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THE OCEAN OF AIR







BY THE SAME AUTHOR.

Sun, Moon, and Stars. Astronomy for Beginners.
With a Preface by Professor PRITCHARD. With
Coloured Illustrations, 16th thousand. Uniform
with ‘Ocean of Air.’ Price 5s., cloth. .

The late Dr. Pusey wrote to Professor Pritchard, of Oxford :
‘Thank you also for telling me of that vivid poetic book, ‘Sun,
Moon, and Stars.” Written so religiously, it is a most fascinating
book, and would at once awaken a young mind to the glories of
the creation, and the manifold wisdom of the Creator. It takes
one’s breath away.’—Z. B. P.

The World’s Foundations. Geology. for, Be-
ginners, With Illustrations.. 5ththousand. Uniform
with ‘Ocean of Air.’ Price 5s., cloth.

‘The exposition is clear, the style simple and attractive.’—
Spectator.

Among the Stars; or, Wonderful Things in the
Sky. Astronomy for Children. With Illustrations,
4th thousand. Price 53.

*We may safely predict that if it does not find the reader with
a taste for Astronomy, it will leave him with one.’—Anowledge.

Father Aldur. The Story ofa River. For Children.
With Sixteen Tinted Illustrations. Price 5s., cloth.
‘The nature of tides, the formation of clouds, the sources of

water, and other kindred subjects, are discussed with much
freshness and charm.’ —Saturday Review.









Lightning. From a photograph by Louis S. Clarke.
By permission of the Royal Meteorological Society.



THE OCEAN OF AIR

METEOROLOGY FOR BEGINNERS

BY

AGNES GIBERNE

AUTHOR OF
‘SUN, MOON, AND STARS,’ ‘THE WORLD'S FOUNDATIONS,’ ETC

WITH A PREFACE

BY THE LATE

REV. C. PRITCHARD, D.D., F.R.S., ere.

Savilian Professor of Astronomy in the University of Oxford

* He causeth the vapours to ascend from the ends of the Earth,

He maketh lightnings for the rain :
He bringeth the wind out of His treasuries.’
Psa. cxxxv. 7.

\ : FIFTH THOUSAND

LONDON
SEELEY AND CO. LIMITED
Essex STREET, STRAND
1894



PREFACE

‘In the year 1879, the proof sheets of a little work
entitled ‘Sun, Moon, and Stars,’ now happily well
known, were placed in my hands bya friend who asked
‘me to give a passing glance over their contents. The
work appeared to me to be so excellent of its kind, and
‘gave, as I thought, so much promise of public useful-
ness, that I volunteered gratuitously the offer of a
Preface, if it were thought that I might thereby con-
tribute to its wider circulation among the intellectual
and educated classes, whether older or younger in
years. Since then I have been gratified by the fulfil-
_ment of this vaticination in the recent appearance ofa
thirteenth edition, and I think it will be for the public
advantage if it shall be even more extensively read.

A. few weeks ago, the same authoress sent me the
revised proof of the present work on the varied and
wonderful properties of the OCEAN oF AIR which
surrounds our earth, and requested my opinion on the
execution and value of the contents. I confess, at first
thought, I considered that so extensive and coniplex a
Subject required an amount of study and of accurate
information which could hardly be expected from an



vi Preface.

unprofessional author. It would, as it seemed to me,
tax the cultivated powers even of a Sir John Herschel,
and if successfully executed might take its place along-
side of his remarkable ‘ Familiar Lectures.’ After an
hour’s cursory perusal, I found myself enchained by
the multitude of pleasant thoughts suggested by the
description of the physical circumstances surrounded
by and immersed in which we pass our being; expressed,
moreover, in language at once so graphic and so simple,
that I offered, for the second time, to exert any in-
fluence which I might possess in the recommendation
of the book to the general notice of educated persons.
The points touched upon in the course of the work
are very multiform, embracing the greater part of the
natural phenomena familiar to us in our daily experi-
ence. Heat and cold, the calm and the storm, thunder
_and lightning, vapour and cloud, and rain and dew,
the passage of light and of sound, each and all of them
in their turns, receive their share of illustration in the
most pleasant of literary styles. Nor does the authoress
hesitate to encounter the marvellous conflicts of the
molecules constituting the phenomena of atmospheric
pressure and of heat and light; while, in due course,
. she extends her flight to the regions of the Aurora and
of the meteoric dust there floating and luminous, then
gradually falling on the earth and on the wide ‘surface
of the ocean, and ultimately dredged up in the form
of mineral nodules from the remotest depths of the
Pacific. A pleasant diversion is then made to the
flight of the birds of the air, and to the locusts which
are driven onwards by itswinds. It is bya fascination |
of this sort that the reader is, almost unconsciously to
himself, led toa general conception of the plan and the



Preface. vii,

!

forces of that part of the course of Nature amidst
which:he draws his breath and lives.

There are more aspects than one in'which a little
work like the present may be intrinsically valuable, and
in which that value reaches to young and old alike.
As‘to the young, it cannot fail to excite those faculties
of curiosity and imagination, which, when restricted
to their proper sphere, are among the most valuable
of our natural endowments. In most cases it will
probably satisfy the curiosity which it excites.

In respect of those who are of an older growth,
it must not be forgotten that though most of us -
are not called upon to become philosophers: or
experts, still we can, all of us, if we choose, obtain
a general and intelligent conception of the nature of
the phenomena in the midst of which we live and
move and have our being. The amount and the
‘intrinsic accuracy of our conceptions of these pheno-
mena need not be great for the ordinary purposes of
life; but to remain wilfully and purposely ignorant of
their existence and their meaning, is hardly worthy of
beings who rank themselves among the rational orders
of the creation.

It will also be found, I think, that very many of our
mental enjoyments spring from a knowledge which is far
from complete or profound, and that the most pleasant
of them are associated with a knowledge which is com-
paratively superficial. It is in the by-plays, the parerga,
of the intellect, that the better part of intellectual en-
joyment is found. It is in this direction, I think, that
we are to look for the chief recommendation of the
little book before us. Beyond this, a casual remark
here and there will probably touch chords within the
trind, which, once ‘so touched, will never cease tc



viii Preface.

vibrate and lead to trains of thought and occupation
at once harmonious and beneficent. In this way, a few
specks of dust swept up from the hearth and placed under
a modern microscope, have revealed to the instructed
eye the wonders of a tropical jungle and the formation
of: coalfields therefrom, and thereby have fired the
mind with a passionate desire for more extended know-
ledge of the primeval formations of our globe, and of
the structure of the grasses which once have clothed
them. It is trifles and accidents such as these which
not rarely have determined the whole bent and aim of
, éntellectual life.

Lastly, I think, there is another aspect under which
this unpretending little book may possess a considerable
value, and it is this: The education at our great public
schools, and even at our Universities, is yearly becom-
ing. more technical, and is falling more and more under
the domination of cram, and of the séhedule, and of
the syllabus, and of the examiner. The schoolboy is
fast becoming hot pressed. He is urged, by considera-
tions which he cannot resist, to maintain or extend the
credit of his school, either by conventional distinction
in Greek or Latin, or in what is miscalled natural
science; or, if he be hopeless in these directions, he
must, at all events, contribute to its fame by athletic |
feats. Thus his young life is marked out for him and
trammeled within narrow limits, while the actual bent
of his mind and the true reach of his natural capacity
become ignored or unsatisfied. In the palmy days of
the old school-life the boy who made but a poor figure
in his form might betake himself to collecting butter-
flies or beetles, or to keeping mice and dissecting them
when dead. In this way the foundations might be laid
for pursuits in life leading to eminence and usefulness.



Preface. ix

As things are, his natural curiosity too often is stifled,
that ‘forward-looking faculty,’ his imagination, becomes
atrophied, and his mental endowments moulded into
a stereotype. From my professional position at the
University, it is my misfortune to observe and deplore
a very large and mischievous amount of this suppres-
sion of curiosity, and a general absence of a knowledge
and love of Nature, which I take to be the necessary
consequence of the modern style of education, when
pushed, as it often is, to an extreme. I cannot doubt
but that the eminent and highly cultured scholars who
adorn the headships of our noble public schools per-
ceive and deplore this result of a system which, through
the varied pressures of social life, they are at presen-
unable to control.

It is here that I think this little volume, with its
multitudinous and interesting peeps into the nature of
the things around us, may become signally useful. If
I had now the opportunity which once I had, I would
place Miss Giberne’s little volume in the hands of the
boys in the upper forms of the school, and encourage
them to read it as an amusement and for a change of
pursuit, under the hope that the pleasant,and varied
information it contains might find a response and a
home not reachable by the ordinary routine of school-
life. What I have here indicated as serviceable
for boys, is at least equally so for the other sex; nor,
as I have already said, do I think its interest or utility
is limited to the years of our youth, seeing that it was
not without a species of fascination that I read it
myself. It is, indeed, but a Httle book, but it treats
of many objects and many phenomena of constant
occurrence, and it possesses the great advantage that it
can be taken up and laid down again piecemeal, and at



x Preface.

fragments: of time. . Bread ‘thus’ cast: upon :the waters
willbe: found hereafter in an abundant harvest. of
~pleasant associations for hours of contemplation or of
leisure: éev.

C. PRITCHARD.

UNIVERSITY OBSERVATORY,
October, 1889.



AUTHOR’S PREFACE

AFTER the generous words of Dr. Pritchard about my
little book, there is small need for me to say much.
First and foremost, I must express my hearty gratitude,
not only for the warm praise which he has accorded,
but also for the infinite trouble which he has taken in
reading the Revise, pointing out some weaknesses and
here and there suggesting improvements. I can never
forget what I owe to his kindness, both with this book
and with ‘Sun, Moon, and Stars.’

In writing ‘The Ocean of Air,’ I have had a wish
to make it one in a trio of volumes. It may be said to
occupy a position between my two earlier scientific
books. ‘Sun, Moon, anp Stars’ had for its subject
the vast realms cf space, dotted with suus and worlds.
‘THE Wortp’s Founpations’ had for its subject the
Crust of our Earth, and the Story of that Crust’s for-
mation. ‘THE OCEAN oF AIR’ has for its subject
the expanse dividing the two—that broad belt of Atmo-
sphere, which rests upon Earth’s Crust and reaches
upward to surrounding Space.

I might end with a catalogue of hooks.and Cyclo-



xii Author's Preface.

pzdias to which I have had recourse for information ;
but many of them are referred to in the following pages,
and the entire list would be cumbrously long. So I will
only close with a word of particular acknowledgment
to the authors of any extracts which I have ventured
to make without writing to ask express leave. I trust
that, in such cases, the omission will be pardoned.

WorTON HOUSE,
EASTBOURNE.

October, 1889.



CONTENTS

PART I.
USES OF THE AIR-OCEAN.

CHAPTER VAGâ„¢
I. THE AIR IN WHICH WE LIVE - - - - 3
Il, WHAT THE WORLD WOULD BE WITHOUT AIR - 15
III], THE WEIGHT AND STATE OF AIR - - - 23
IV. AIR AS A MIXTURE - - - - - 33
V. AIR AS A PART OF EARTH - - - - 38
VI. THE RESISTANCE OF AIR - - - - 44

PART II.

GASES OF THE AIR-OCEAN.

VII. TIIE USES OF OXYGEN - - - - 85
VIII. WHAT IS MEANT BY BURNING - - - 62
IX. THREE FORMS OF CARBON” - - - - 70
X. THE PERILS OF CARBONIC ACID - - - 75
XI. WHAT IS MEANT BY BREATIIING— - - - 89
XII. HOW PLANTS WORK - - . - - 102
PART If,
VAPOURS OF THE AIR-OCEAN.
XIII, WATER IN THE ATMOSPHERE | - - - 113
XIV. ABOUT EVAPORATION - - - - - 121
XV. ABOUT CONDENSATION - - - - 129
XVI. DEW, MIST, AND FOG - - - - - 135
XVII. THE MOUNTAINS OF CLOUDLAND~ - a - 143

XVIII, RAIN, SNOW, AND HAIL - - - - 153



xiv Contents.

PART IV.
MOVEMENTS OF THE AIR-OCEAN.

CHAITER . PAGE
XIX. THE NATURE OF WIND -. - - - 165
XX. THE CIRCULATION OF AIR: - - - - 17>
XXI. MORE ABOUT THE WILD WINDS” - - - 181

XXU. THE GREAT WATER-CIRCULATION - - - 190

PART V.
DISTURBANCES OF THE AIR-OCEAN. |

XXIII. CLIMATE - - - - - - 203

XXIV. WEATHER - .- - - - - 212
XXV. EDDIES OF AIR - - - - - 221

XXVI. WHIRLWINDS AND TORNADOES - - - 230

XXVII. THUNDER AND LIGHTNING - - - + 239

PART VI.
FORCES OF THE AIR-OCEAN.
XXVIII. ELECTRICITY AND MAGNETISM - - - 245

XXIX. HEAT - - - - - - - 259

XXX. SOUND AND LIGHT - - - - - 270

XXXI. ATOMS AND MOLECULES - - - - 283

XXXII. A BUSY WHIRL - - - - - 290
PART VIZ.
LIFE IN THE AIR-OCEAN,
XXXII, DUST OF THE AIR. - - - - - 299
XXXIV. LIVING DUST OF THE AIR - - - - 311
XXXV. INSECTS OF THE AIR - - - - 316°

XXXVI. BIRDS OF THE AIR -_ -. - - - 325



LIST OF ILLUSTRATIONS

Engraved, by permission, from Instantaneous Photographs,

PAGE
LIGHTNING - - - - - - Frontispiece

THE YACHT ‘MOHAWK’ IN A BREEZE - - - I

ao

CLOUDS OVER LOCH EIL, FROM THE SUMMIT OF BEN NEVIS 12

iS}

MIST - - > - - - - - 136
HOAR-FROST - - - - - - 140
CLOUDS ON THE HIMALAYAS = - - - - 146
CUMULUS CLOUDS - - - - - - 150
SNOW ON THE WESTMORELAND MOUNTAINS - - 156
ICICLES FROM A WATERFALL - - - 160
WIND-BLOWN TREES - - - - - - 168
BREAKERS AT BOGNOR - - - - ~ 84
WAVE BREAKING OVER TIIE SEA-WALL AT BOGNOR - 186
SNOW ON THE SLOPES OF THE HIMALAYAS - - - 204
A WAVE AT HASTINGS - - » - - - 226
A FROZEN TORRENT + . . - - - 262

FLIGHT OF SEA-BIRDS - - - - - - 326



PART I.
USES OF THE AIR-OCEAN,



CHAPTER I.
THE AIR IN WHICH WE LIVE.

Our Earth has many robes.

Closely-fitting garments come first, of brown soil
or gray rock and green grass, with wide liquid under-
skirts of deep blue filling up the spaces between.

Outside these are coverings more wonderful still;
fragile yet strong, transparent, almost invisible, folded
around layer upon layer, or, as one might say, veil
upon veil, each more gossamer-like than the last.

These form Earth’s surrounding Atmosphere—a
substance pervading everything, found everywhere.
One may travel from the equator to the poles, one may
journey by sea or by land, one may soar high in a
balloon or descend deep into a mine, but one can
never in this world go to a place where the Atmosphere
is not. —

A substance—for air can be felt; air has weight; air
occupies space; air, like any other body, can be made
hot or cold; air is composed of particles of substantial
matter.

A child, not to speak of a grown-up person, opening
a box which holds only air, will naturally say, ‘ Nothing
here!’ But something is there; something very definite
and real, and of no small possibilities. Those same
quiet air-particles, actually unfelt by the hand moving

I—2



4 _ The Ocean of Air.

gently among them, have strength, when stirred into a
hurricane-blast, to uproot huge trees, to sweep away
vast buildings, to raise ocean-waves upon which mighty
ships are tossed helplessly about ‘ like eggs in a boiling
cauldron.’

Air may be felt. The faintest breeze cannot stir
without a man becoming conscious of the air-particles
striking against his face. He cannot ride or run
through the air without the same sensation. If he
even moves his. hand quickly enough to and fro he is
aware of something resisting his hand.

Air can be made hot or cold. We all know from
experience the difference in our feelings when cold air-
particles on a frosty winter’s day, or hot air-particles
on a sultry summer’s day, strike against our bodies,
either giving over to us of their heat, or stealing away
some heat from us.

Air also has weight, and occupies a certain amount
of room. Just as a mass of iron or of lead weighs so
much, a mass of air has its own particular weight.

This means that air, like iron or lead, is subject to
earth’s attraction ; which is only tantamount to saying
again that air is a substance. Nothing which is not
a substance can possibly be attracted by a substance.

If air is a substance it must occupy space, it must
take up room. It may be very light, very slight, very
elastic, and very compressible. Other bodies may pass
easily among the air-particles, pushing them apart, or
squeezing them closer tog-ther. Yet space it must
have. Air, being distinctly a something, has to be
somewhere.

Air has a faint bluish tint, which on a sunshiny day
becomes in the sky a very pure and deep blue. This



The Air in which we Live. 5

tint is not believed to be the natural colour of the
atmosphere. Were it so, the air would merely act the
part of a blue pane of glass, rendering the white light
of the sun blue as it reaches our eyes; but the blue of
the atmosphere is known to be a reflected blue.

If reflected, there must be something in the atmos-
phere to reflect it; and such indeed is the case. Per-
fectly pure air would doubtless be without colour, but
perfectly pure air we do not find. The whole atmo-
sphere is full of multitudinous minute specks, so small as
to be in themselves invisible, so light as to remain aloft.
To the presence of these the blue tint is believed to be
due. They scatter the light of the sun, and prosace
the blue effect.

A beam of strong white light, caused to pass through
a liquid which contains a large supply of minute floating
particles, is affected by them in a like manner. The
short blue waves are more abundantly reflected than
the long red waves ; and so the water seems to be blue.
This explanation serves for the deep-blue colour of the
ocean, as well as for the blue of the atmosphere.

The whole Earth is surrounded by this marvellous
Air-Ocean; an ocean of gaseous matter, at least one
hundred times as deep as the water-ocean.

At the bottom of the gaseous ocean we small
human creatures crawl about, commonly on flat lower
levels—the ocean bottom, in fact. Sometimes, with
much toil and trouble, we climb the little ridges and
mounds called ‘ mountains ;’ little compared with the
depth of the atmosphere, though not little compared
with ourselves. The highest mountain-peaks of even
the vast Himalayas lie low down near the bottom
of the Ocean ot Air.



6 The Ocean of Air.

Our position is, on a bigger scale, much the same
as that of the crabs and cray-fishes crawling laboriously
about;at the bottom of the sea-water tanks in the
Brighton Aquarium. Only, they are in a minute world
of water, and we are in a large world of air. They
have over their heads only a few feet of the fluid*
in which they live. We have over our heads many
miles of the fluid* in which we live.

Also, it seems probable that they cannot see beyond
their confined regions of water, while we have eyesight
which can pierce far beyond our wide regions of air.

But the very extent of the Ocean of Air adds to our
difficulty in studying its nature. All observations that
we can make must be limited by the state of the
atmosphere just around ourselves. We can never get
out of and beyond the atmosphere, so as to see it asa
whole. At any time a slight local fog is enough to put
a stop altogether to such observations, beyond the
unpleasant experience of the fog itself.

Just so a crab, wishing to study the general condi-
tion of the water in his tank from one corner of it,
would be hampered by the stirring up of a little mud
or sand in his own neighbourhood.

In all study of Earth’s airy envelope we have to
allow for these difficulties ; to confess ourselves apt to
blunder; and not to dogmatize hastily upon questions
about which we are not well informed.

We can never in this life get beyond the Ocean of
Air; for man and beast cannot live without air. To
breathe means life; to cease breathing means death.
That which we breathe is the air around us—the ocean
of almost invisible gases.

* Air and water are both ‘fluids,’ though different in kind,



The Air in which we Live. ”

It used to be supposed that the atmosphere reached
only to a height of about fifty miles above Earth’s
surface.

We are driven here to conjecture, to some reason-
ing from certain tokens, and perhaps to a good deal of
guessing. Being always imprisoned at the bottom of
our ocean, we cannot measure for ourselves how far it
extends above.

Of late years the opinion has gained ground that
the atmosphere reaches to a height certainly of two or
three hundred miles, probably of four or five hundred,
possibly a good deal more. But the condition of the
air far above is different from that of the air in lower
levels, where we live and breathe.

The higher we ascend, the more thin or ‘rare’
becomes the air. A less quantity fills a certain space
up there than down here. The particles float farther
apart one from another.

This difference in the density of the air is chiefly
due to Attraction.

Each separate air-particle is drawn steadily earth-
ward by the Force of Gravitation, and that force is
stronger on the surface of earth than at a distance.
The closer to earth, the heavier the pull; the farther
from earth, the less the pull.

Besides the actual attraction of the earth drawing
the air-particles downward, there is the great weight
of the whole atmosphere above, caused by the same
attraction. Miles and miles of air overhead press
mightily downward, packing tightly together the lower

layers of air near to earth’s surface.

If thousands of bales of cotton-wool were piled
into an enormous heap, the upper layers might be
light and loose in their make, but the lower ones would



8 The Ocean of Air.

be squeezed into a very small compass by the pressure
of the mass above.

Without this pressure of the overlying atmosphere,
the air down here would not be nearly so dense as it
is; and, indeed, would not be fitted to support life. A
man ascending a mountain or rising in a balloon leaves
heavy layers of air below, and has an ever-lightening
weight above, so that the atmosphere around him be-
comes constantly more thin, more difficult to breathe.

This difficulty is felt to a severe extent by those who
climb the greater mountains. Within certain limits of
height the air is only more light and exhilarating, be-
cause a little less dense, than on the plain. But as its
rarity increases, the breath gets short, the heart’s
action is quickened, the sense of oppression grows
painful. If the ascent could be continued indefinitely,
death from suffocation would result. »

The loftiest mountain-top upon earth stands only
about five and a half miles above the sea-level. No
man has ever yet climbed to such a height, and pro-
bably no man ever will. It might not be impossible
to exist for a while upon the summit, but one can
hardly imagine any man able to reach any such level
by climbing. The thinness of the air must long
before have so reduced his powers as to render active
exertion out of the question. If some means could
be devised for bearing him to the summit of Mount
Everest, loftiest of the Himalayan range, he would
probably, when there, be fit for little more than to lie
panting on the ground.

Mount Everest* has never yet been scaled by men,
though ardent mountaineers long ago reached to a

* Mount Everest is over 29,090 feet high; Chimborazo, over
19 500 feet ; Mont Blanc, over 15,700 feet.



The Air'in which we Live. 9

level of over 19,000 feet in the Himalayas. This, too,
has been done with the monsters of the Andes chain,
once supposed to be the highest. mountains in the
world, though now known to be far surpassed by the
giants of North India.

In the beginning of the present century Humboldt
made a vigorous attempt to scale Chimborazo, one of
the loftiest of the Andes. He and his party suffered
severely from sickness, giddiness, and difficulty in
breathing, and the attempt proved a failure. Not till
over seventy years later was the ascent actually
accomplished by Mr. Whymper.

This time, too, the daring climbers were almost
incapacitated by weakness, headache, fever, and breath-
lessness, yet with desperate resolution they held on
till the summit was gained. After camping for a night
at a level above the utmost height of Mont Blanc,
they stood at length victorious, nearly 20,000 feet above
the sea. ‘Theascent of the last thousand feet,’ we are
told, ‘occupied five hours;’ for a large tract of ex-
traordinarily soft snow had to be crossed, and ‘it was
found necessary to flog every yard of it down, and
then to crawl over it on all fours.’ Such exertions, at
so great a height, and in so rare an atmosphere,
speak well for the indomitable spirit of the travellers.

De Saussure, ascending Mont Blanc in August,
1787, suffered from extreme distress and exhaustion.
On the highest ridge he had to halt every fifteen or
sixtcen steps, sometimes even to lie down; and the
robust guides with him were in absolute danger of
fainting. The same excessive weakness was felt by
certain other well-known climbers in 1844. But this
experience is by no means universal. The effect of the
rarefied air differs extremely with different individuals.



10 The Ocean of Air.

Moreover, use greatly modifies and even to some extent
does away with these effects. In the Andes there are
cities full of people, at a height of 12,000 or 13,000 feet,
and no inconvenience results from the thinner air,

Carried upward passively in a balloon, without effort,
men have risen higher than the highest mountains.
Mr. Coxwell and Mr. Glaisher in their celebrated aerial

re An Oa, Onflens

> voyage of 1862 are believed to have mounted seven

3 miles above the sea. No little peril and suffering

© were involved, alike from the extreme thinness of the
Se air, and from the bitter cold.

The wish to fly like a bird is an old wish among
men. Perhaps it is a form of the restlessness which
dislikes to be tied down anywhere; perhaps it partakes
of the ‘excelsior’ feeling which would fain reach
regions inaccessible. Tied down we undoubtedly are
to the lower depths of the Air-Ocean, and inaccessible
the higher regions undoubtedly are to us.

Various mad attempts at flying have been made
from time to time, more or less disastrous to the
makers of them. When, however, near the close of
the eighteenth century, a balloon was first made and
sent up, men thought they had at last won the mastery
of the atmosphere. They did not at once find out that
floating is not flying; that the balloon at its best is still
only ‘an unmanageable despot’—a despot over the
men whom it carries, and itself a complete prey to the
despotic winds and breezes.

No means of steering or guiding a balloon has yet
bcen discovered.* Where the air flows the balloon goes,

Aen? fA thahe th,

dl

/ ar

i

; CK/
C An 1909

* Attempts are now being made to construct an ‘air-ship,’ able
~ to plough its way through opposing winds ; whether successfully
or no, time will show.

a



The Air in which we Live. II

fast or slowly, according to the degree of wind. No
balloon ever cuts its way through the wind, or travels
contrary to a breeze; it is simply swept to and fro by
the atmosphere, as a cork is borne to and fro by the
ocean.

The first public balloon ascent took place in June,
1783. A fire-balloon, made of linen and said to be filled
with smoke, went up from near Lyons, and a furore of
excitement followed. Silk balloons, filled with hydrogen
gas, were made next,‘and the earliest ascent of man
followed. A successful though perilous attempt to
cross the Channel took place about two years later.

Many aerial journeys were made, some ending well,
some fatal to the unfortunate voyagers. As the dangers
of these attempts became better known, and as their
comparative uselessness for almost all except scientific
purposes grew more apparent, public interest in the
matter faded. During the early half of the present
century balloons were little thought of; but more lately
there has been a revival of interest.

Some very remarkable ascents have been made by
the famed aeronauts, Mr. Coxwell and Mr. Glaisher.
One or two of these are especially worth mentioning.

In their second ascent from Wolverhampton, the
balloon sprang rapidly upwards, and in about ten
minutes was hidden by a cloud. It reappeared ;
vanished again; was seen at a height of perhaps
three miles; disappeared anew; then gleamed in the
far distance as a transparent ball, shining moon-like in
the sunbeams. The journey lasted from about one.
o’clock till half-past four; and in that interval the
balloon ascended four miles and a half.

The voyagers suffered from severe ‘sea-sickness,’
though not from bleeding of the nose or singing in the



12 | The Ocean of Att

ears, popularly expected on such occasions. They had
enough to bear without these additions. Mr. Glaisher
held manfully to his task, observing and noting down
the state of the atmosphere minute by minute, despite
sickness, brain-pressure, violent headache, and a pulse
at 108 per minute, all due to the rarity of the air.

The view seen from above must indeed have been
marvellous. No veil of intervening clouds shut off
what lay below, and the earth was visible, not asa
rounded surface, but as a seeming hollow, with a
distant horizon rising high all around, like the.rim of a
saucer or an inverted watch-glass. The intense black-
blue of the sky, as seen from great altitudes, is well
known to mountain-climbers. Here, however, the blue
seemed to be everywhere; a mighty expanse of pure
blue filled the vast hollow, reaching to unlimited depths
above; ‘an immense shoreless ocean ’—the Ocean of
Air in which these daring voyagers floated. A ‘ bound-
less sea’ of ever-changing clouds, piled in mountain
masses, and dazzling the eyes with their snowy glare,
followed more or less the lines of the horizon, often
closing in below to shut off the solid ground.

As the balloon rose higher, the pervading blue grew
brighter, and earthly sounds waxed faint.. One mile
high, human voices might still be heard, raised in a
shout ; two miles high, only a dog’s sharp bark could
be distinguished.

Since a balloon moves with the moving air, there
are no jars or jolts, no struggles to advance, as with
a ship at sea—-nothing resists its passage. The
movements of a balloon seem, indeed, to be charac-
terized by a singular quietness, so far as regards the
voyagers’ sensations. When it first rises, the earth
appears to drop away: when it descends, the earth



The Air in which we Live. Iz

appears to rise. There is little consciousness: of
motion. i

This delusion was quaintly expressed by a certain’
American aeronaut. He was, he says, ‘ preparing to
come down gently, when the earth bounced up against
the bottom of his car.’ A more terse description
could scarcely be offered.

The most remarkable ascent known was that of
Mr. Glaisher and Mr. Coxwell on the 5th of September,
1862, when they rose seven miles. If we remember
that Mount Everest, of the Himalayas, is nearly twice
the height of Mont Blanc, and that the voyagers were
floating a mile and a half higher than the height of
Mount Everest’s topmost peak, we shall better imagine
the perils of this excursion. No human beings have
ever ascended further. The marvel was that they re-:
turned to earth alive.

In those lofty regions of the Air-Ocean no living
creatures exist. The voyagers passed through bound-
less silent solitudes—silent except for the hurried beat-
ing of their own hearts, the sound of their own panting
breath, the sharp ticking of their watches, and the
‘clang of the valve door.’

On leaving earth the thermometer stood at 59°.
Soon afterward the balloon passed through masses of
cloud, thousands of feet in depth, then came out into
dazzling sunshine, with a deep-blue sky above and
countless mountain masses of billowy cloud below.

As they rose, they released at intervals a captive
pigeon. One set free at a height of nearly five miles
‘fell downward like a stone.’ Of two others taken
higher, one died of the cold and the other was stupefied.
When they reached five miles above the sea, the tem-
perature was below zero.



14 The Ocean of Air.

Still upward, further upward, rose the resolute pair.
Then blinding darkness and insensibility seized Mr.
Glaisher. Had he been alone, he could never have
revived. With no one to open the valve, the balloon
must have carried him onward into yet higher and
deathlier regions, where for lack of air he would have
perished. ;

Even then Mr. Coxwell did not at once give in; but
he was strictly on the watch. At the seven miles’ level,
a tremendous height, he too felt signs of failing con-
sciousness. In a few minutes more all would have
been over with them both, and at last he yielded. It
was indeed time that he should. His hands were
powerless to act, but he seized the valve-rope in his
teeth and pulled. The gas rushed out; the balloon
steadily sank. Both lives were saved, and a mighty feat
had been accomplished.

Yes, a mighty feat, and a tremendous height—in
consideration of human powers! Seven miles high
would seem to be the outside limit at which animals
generally can exist for even a short time. Birds may
be to some extent an exception. Certain birds are
believed to soar occasionally two or three miles higher
still.

But what are seven miles—what are even ten miles—
compared with the four or five hundred miles of atmo-
sphere-depth ? With all our utmost efforts, we and the
birds still find ourselves only able to creep and flutter
on or near the floor of the Ocean of Air.



CHAPTER II.
WHAT THE WORLD WOULD BE WITHOUT AIR.

Wuat Earth would be without her surrounding Ocean
of Air, we can scarcely imagine.

The Atmosphere plays so extraordinary and essential
a part in all around, that to picture its entire absence is
not easy.

We see faintly on the moon something of what an
airless world must be. Yet since we only ‘see’ froma
distance of two hundred and forty thousand miles, that
does not mean much. Imagination has to come in,
and imagination is apt to play us curious tricks when
running after affairs which lie outside the range of
human experience. —

No man has ever yet been to an airless world. If
he could get there, he could not live there ten minutes.
He would be worse off than the aeronauts seven miles
above earth’s surface. They had at least some air,
though but a scanty amount; while he would have
absolutely none.

Without air, man and beast cannot breathe. With-
out air, plants and trees cannot grow. Without air, life
as we know it—the lower animal life common to man
and beast—is a thing impossible. Without air, our
world would be, as we suppose the moon to be, a world
of lifelessness.

Air is earth’s outer robe, ‘for use and for beauty ’—~



16 The Ocean of Air.

for use in modes uncountable; for beauty, not so much
in itself, as in the softening, the diffusing, the con-
trolling effects of its presence.

Air is a mighty Ocean, in which all things living
must dwell. Even the living things of the sea are not
exceptions to this rule, for water itself is pervaded by
air. A man, going into and under water, does not get
beyond the touch of air; only, not being provided, like
fishes, with breathing gills, he cannot make use of
what is there—he cannot separate the air from the
water, and so keep himself alive by breathing it.

Some animals living in the water-ocean are as
dependent upon the Air-Ocean as man himself for ‘ the
breath of life.’

Whales are a remarkable example of this. They are
not fishes, though often mistakenly called so, but belong
to the same ‘family’ of creatures as men and land-
quadrupeds generally. A whale is warm-blooded, has
no gills, and breathes atmospheric air, coming to the
surface for it.

A whale, kept forcibly for a long while under water,
would be drowned exactly as a man would be... If
a whale is thrown upon the shore, it does not die of
suffocation, but of inanition. A fish’s gills are no more
fitted to breathe air in bulk, than a man’s lungs are
fitted to breathe air diffused in minute particles through
water. The fish out of water is suffocated by getting
air too rapidly: the man under water by exactly the
reverse. A whale breathes like a man, and on land it
simply starves fast from lack of the incessant food re-
quired by such a huge carcase.

There is a difference certainly between man and
whale in the matter of breathing. A man has to take
in fresh supplies of air constantly, and if he is beyond



What the World would be. without Air. 17

xeach of air for more than’a few minutes he dies. A
whale comes to the surface for about: ten. minutes,
spouting out enormous supplies of used-up air and
taking in enormous supplies of fresh air, after which it
can remain under water for half an hour or more :. some
say an, hour. Then a fresh bout of noisy breathing
becomes an absolute necessity.

This, however, is merely a matter of internal
arrangement. The whale has an immense reservoir
of blood, which, being thoroughly. purified by the air
during ten minutes of vigorous breathing, serves slowly
to supply the creature’s requirements while below. But
the need for air, and the effect of that air upon the
blood, are much the same in man and whale. ~

Small creatures, as well as large ones,. spending
much time under water, and yet breathing air, have to
come regularly to the surface.

The great water-beetle, for instance, while able to
live on land, is a very incapable being there, and seems
at home only in the water. Like other insects, it has
no lungs, and breathes air into its body through tiny
holes in its sides. Lungs or no lungs, air it must
have, or like man and whale it must die. So, after the
fashion of the whale, it rises to the surface to breathe,
:and not having the happy internal arrangement of the
whale, one would expect it to be compelled to dart up
incessantly for fresh air. But here we find another
Provision, equally wonderful. ;

The hard polished wings of the beetle, neatly fitting
and fast shut, inclose between themselves and the body
a water-tight hollow, into which the breathing holes
open... This hollow is filled with air when the creature
comes to the surface of the pond, and while the little
supply is being gradually breathed, the beetle may

2



18 The Ocean of Air.

safely remain below. Not till it is used up does a
journey to the surface for a fresh supply become neces-
sary.

Another such instance is seen in the water-spider,
a creature, again, which can exist on land, but is
more at ease in water. When the spider dives, it
carries downward countless tiny air-bubbles, caught
and imprisoned among the fine hairs which cover its:
body.

This is not all. The spider has also an extra-
ordinary power of conveying down at will, between
body and folded legs, a large bubble of air for a par-
ticular purpose—to supply the little home below. The
said ‘home’ is a cocoon, spun by the female spider in
readiness for eggs. Having prepared a cocoon, the.
spider dives with a big air-bubble, and lets it loose
within the cocoon, where it remains, driving out an
equal quantity of water. Bubble after bubble being
carried to the spot, all the water in the cocoon is.
gradually replaced by air, and the tiny dwelling becomes.
habitable.

So much as to the need of air for living creatures.
If our world had no Ocean of Air, there could be on
earth no men, no quadrupeds, no whales or fishes, no.
birds or insects, no forms of life.

Like the ocean of water, the Ocean of Air knows no.
repose or stagnation. What we call stillness on the
most sultry of summer days does not mean absolute.
stillness. Though not enough wind may stir to lift a
feather, yet the air is in ceaseless motion, to and fro,
hither and thither. The whole atmosphere is a vast
and complicated system of air-currents, and each lesser
portion of air has its own lesser circulation. You





The Vacht“ Mohawk” in a Breeze. From a photograph by G. West & Son.



What the World would be without Air. 19

cannot lift your hand without causing a tiny breeze;
you cannot turn a wheel without making a minute
whirlwind; and every separate air-movement draws
other movements in its train.

There is water enough on earth for all needed
purposes; but we should find ourselves in direful
straits if the whole water-carrying from lakes and
rivers for men and animals had to be performed by
human agencies.

Far from this, a mighty apparatus is provided.
The scanty aid that man can give only shows how
little he is capable of.

The entire atmosphere is a tremendous pumping-
engine, an enormous watering-machine, always at work;
always recciving supplies of liquid from the ocean, from
seas, lakes, rivers; always showering this water down
again upon the land, as needful drink for plants and
animals, as needful cleansing for all things.

Air, the great carrier of water, in its wonderful
strength and restlessness, bears vast layers of cloud to
and fro, wafts away superfluous damp, drenches the
dry and thirsty earth, fills ponds and lakes, feeds—nay,
actually makes—the rivers, never flags in its ceaseless
energy.

If clouds hang low or fogs arise, we are glad of the
moving air which sweeps them elsewhere. If the soil
is caked and plants droop, we are glad of the moving
air which brings rain.

Thus our wants are supplied, and the wide Water
Circulation of earth is carried on. Without circu-
lation, without motion, stir, change, there cannot
be life. Stagnation must mean death. Our Earth,
without her Ocean of moving Air, would be a world of
death.

2—2



20 - The Ocean of Air

Without air, Earth would be in great measure a
soundless world. Silence would reign here, as pro-
bably it does reign on the moon.

Sound, as it commonly reaches our ears, depends
for its very existence upon air. Let the concussion of
two bodies be ever so mighty, if there were no air to
bear away the vibrations of that concussion, there could
be no crash of sound.. True, sound-waves can be
conveyed through a liquid or through a solid as well
as through air; and we might be conscious of the
ground’s vibrations, but our ears would hear no noise.

So an airless world would be a silent world. With-
out air, supposing we could ourselves exist, we should
hear no trickling brooks, no rush of waterfalls, no
breaking ocean waves, no sighing of the wind, no
-whisper of leaves, no singing of birds, no voices of
men, no music, no thunder, no one of the thousand
concomitant sound-waves which together make up the
babble and murmur of country and town. Those only
who are perfectly deaf can know what such silence
means.

Without air our world would not be in darxness;
for light does not, like sound, depend mainly upon air
for its transmission. Light travels through regions
where air is not; and if light is communicated by
waves, they are not waves of air. But though the
absence of air would not deprive the earth of light,
‘it would make a very great difference in the kind and
degree of light received.

Without air the blue sky would be black as ink;
stars would glitter coldly in the daytime beside a
glaring sun; deep shadows would alternate with blind-
ing dazzle, and all the soft tints of sunrise and sunset



Whee the Wold would beret Aine. 88

would be wanting. Earth would be like the almost
airless moon—all fierce whiteness and utter blackness
—with no gray shades, no rosy gleams, no golden
evening clouds; nay, without air there could be no
clouds. =

On the moon is no twilight; for no air-particles
float about, reflecting the sunlight from one to another,
and forming a soft veil of brightness, to reach farther
than the direct sunlight alone can reach.

Sunbeams travel straight to earth, unbending. as
arrows in their flight, and unaided they cannot creep
any distance round a solid body, though they may be
reflected or turned back from it. But the air breaks up
the sunbeams, bends them, diffuses them, spreads them
about, surrounds us with a delicate lacework of woven
light.

A sunbeam travelling through space is invisible till
it strikes upon some object. If that object is solid,
the light of the sunbeam is partly absorbed, partly
reflected ; if the object is transparent, the sunbeam
passes through and onward. Few substances, if any,
are perfectly transparent. We call air transparent, yet
it is so only ina measure. Each sunbeam passing
through the atmosphere loses part of its brightness by
the way, and so the great glare of the sun is softened
before it reaches the lower depths of the Air-Ocean.

The sun’s rays are rays of heat as well as of light.
While the atmosphere softens the glare, giving us
shade and twilight, it also modifies the extremes of
temperature, from which, without air, we should suffer.

When the sun goes down, although we are often
conscious of a chill, it is not the instant and over-
whelming chill which we should feel but for the atmo-
sphere. All day long the sun has been warming the



22 The Ocean of Air.

earth and air. When his direct rays are withdrawn,
the warm air for a while keeps its warmth, and gives
over of that warmth to us.

We talk often of ‘warm winds’ and ‘cold winds’
from different quarters. By ‘warm winds’ we mean
air that has passed over a warm surface of land or sea,
so gathering up and bringing heat to us. By ‘cold
winds’ we mean air that has passed over a cold surface
of land or sea, so parting with some of the heat it had
in a measure, and reaching us in a chilled condition.

People living in England are very much warmer
than their friends across the Atlantic living no further
north. Here the weather is mild when there it is
bitterly cold. There they are ‘frozen up,’ when here
we have only a little fitful frost and snow.

The main reason for this difference is that abund-
ance of soft warm air comes drifting over us from a
certain ocean-current, called the Gulf Stream, flowing
northward in our direction from the tropics. Our
friends across the ocean receive a like abundance of
cold air from a cold ocean-current, flowing southward
from the frigid zone.

All this would be altered had we no enfolding Ocean
of Air.



CHAPTER III.
THE WEIGHT AND STATE OF AIR.

IF one would understand the Atmosphere as a whole,
one must learn something about the laws which govern
its movements.

That air is a substance, and therefore is heavy like
any other substance, has already been explained.

We are apt to talk of things as heavy and not
heavy, as if some things had weight and some had
not. But every substance without exception has
weight.

A certain gas, called hydrogen, does not commonly
fall downward, but rises through the air upward. If
we wish to send a balloon towards the sky, we only
have to fill it with hydrogen gas, and it is sure to
ascend.

Yet, hydrogen gas is a substance, and has weight.
Only its weight is so very much less than the weight
of common air, that the air-particles fall naturally
below, and press the lighter particles of hydrogen up-
ward. This is how a balloon rises; not because it
has no weight, but because it weighs less than air.
A cork has weight, yet in water it springs to the top,
because it weighs less than the same bulk of water.

A feather, light as we count it, has weight, and if
dropped in a closed vessel, emptied of air, it will reach



24 The Ocean of Air.

the bottom quite as fast asa lump of iron. From its:
light and spreading make, it is easily buoyed up and
carried along by the slightest breeze; but if the air is
still it soon finds its way downward.

Until nearly the middle of the seventeenth century,
nobody so much as suspected the fact that air had
weight. When Galileo was an old man of seventy-
six, he was the first to gain a glimpse of the long-
hidden truth; and his pupil, Torricelli, followed out
his experiments, proving him to be in the right:

Weight is caused by a wonderful force or power,
which holds sway, not only on earth, but in the sun
and the planets, and throughout the universe—the
Force of Gravitation.

Every substance attracts every other substance to-
wards itself with a greater or less degree of strength, de-
pendent on the size, the make, and the distance of each.

If no substance attracted any other substance,
there would be no such thing as ‘weight.’ When we
speak of a mass of iron being ‘heavy,’ we mean that
the earth draws it downward. When we speak of the
whole Atmosphere having weight, we mean that it,
too, is pulled earthward.

The attractive force which causes all objects to
draw nearer together, when not prevented, we know
by its effects, and by its effects only. We see what
it does, not what it is. That such a force exists we
perceive; that such a law or order prevails we know.
But what the force is in itself, and in what mode one
substance influences another, none can tell us. Search
as we may, and rightly may, into these things, solving
one perplexity after another, we find ourselves sur-
rounded still by baffling walls of mystery.

We call Attraction one of Nature’s Laws, or one of



The Weight and State of Air. 25

Nature’s Forces. Either term leaves us where we stood
before. The forces of Nature are the forces of the God
of Nature. The laws of Nature are the laws of the
God of Nature; they constitute the ‘Plan’ on which
the Universe and all that is therein are framed. And
because they are His laws, His forces, and because
He is our Father, we, His children, may well search
into them with the utmost of such powers as He has
givenus.

The Air of our almost invisible Ocean is often de-
scribed as an elastic fluid, but this gives no clear idea.
of its condition. A fluid may be either a liquid or a
gas; and liquids are by no means the same as gases.

There are three distinct forms known to us of
the same substances upon Earth. These three states
or forms are—the Solid; the Liquid; the Gaseous. A
simple illustration is to be found in water.

Suppose a man should travel to earth from some
far-off region of space, having never seen our common
earthly substances, having never come across water in
any of its various conditions. He must not, by-the-bye,
‘hail from’ the planet Mars, since there, at least, we
haye good reason to believe, snow not only exists but
thaws, which means the presence of water as well
as of ice.

Suppose, on arrival, he should alight first upon a
Greenland glacier, having hard ice all around him.
He would naturally describe water as ‘a species of
rock.’ For thus far he would know it only in the solid
or frozen form.

If he landed first on the border of the ocean, in a
temperate climate, he would describe water as ‘a
liquid.’



26 The Ocean of Air.

If his first acquaintance with it were in the shape
of steam escaping from a boiler, he would describe it
as ‘a vapour,’ or as ‘a gas.’

He would not at once, without further observation,
know that these three are one and the same substance,
under different forms. He would not yet know that
ice can be turned into water, water into steam, steam
into water, and water into ice. Nor could he guess
that the Force which by its presence or absence works
these changes is Heat.

You have a solid block of ice, and a certain amount
of heat is brought to bear upon it. Gradually the ice
‘becomes water; and the solid has changed into a
liquid. But the substance isthe same. The particles
which form the water are the same which formed the
ice, only under altered conditions.

Again, more heat is brought to bear upon the water
until it boils. Then gradually it changes into steam ;
and the liquid has become a vapour. But still the
substance is the same. The particles which form the
steam are the identical particles which formed the
water, and before that the ice, only a change has come
over them.

If the steam is not allowed to escape, but is kept in
a confined space and cooled down, the particles will
draw together again, and the steam will once more
become water. If the cooling is continued, more heat
being taken away until the freezing-point is reached, it
will turn again to ice.

-To the same ice which it was originally! The
particles of matter are the same. The substance is
not altered. It has merely passed through a scries
of changes of form.

All solid substances are formed of minute particles,



The Weight and State of Air. 27

more or less closely bound together by a certain mutual
attractive power, which we call the Force of Cohesion.

Cohesion means ‘sticking together. When we
speak of the Force of Cohesion, we simply speak of the
Force of Sticking Together.

But to speak of the parts of a substance sticking
together is by no means to say why they stick together;
and to talk of the cause as a ‘force’ is not at all to
tell how it acts.

The ‘how’ of this matter is again beyond us; for
the attraction of cohesion is even more mysterious
than the attraction of gravitation. We see both by
their effects; but we do not know in what manner
those effects are brought about.

In a general way, when we speak of a ‘law’ we
mean a command which has to be obeyed. By a ‘law’
in Nature we mean rather a rule of action constantly
followed by certain bodies under certain conditions.
The word signifies, not that the Divine Ruler has given
definite commands which the world of matter obeys,
but that the Divine Creator has impressed or endued
each particle of matter with certain characteristics
which, under the same circumstances, always result in the
same modes of action or work.

We speak often of substances ‘obeying’ certain
‘laws;’ but since the word ‘ obey’ implies choice and
a possibility of disobedience, it is hardly a correct
term. Each particle of substance merely does in each
set of circumstances, and does inevitably, that which is
its nature to do.

But how and why one minute particle of matter
should differ so utterly in its nature from another is a
profound mystery.*

* Since writing these chapters, I have come across the following



28 : ‘The Ocean of Air.

In addition to the Force of Cohesion, which holds
together the particles of any substance, there is
another and opposite force, sometimes described as
the Force of Repulsion, or the Force of Driving
Away.

It seems singular that two such opposite forces
should be at work in one lump of iron or one piece of
wood ; that the very particles which are trying to get
closer to other particles should also be trying to get
farther from them. Many things in Nature are, how-
ever, brought about by such working of opposite
powers.

We are well able to see a need in the present
case for both, if our world is to remain in its present
form.

Without the force of cohesion there would be no
solid substances at all. The whole earth, and all it
contains, would be a scattered mass of loose im-
palpable dust, too fine for the human eye to see.
There would be no shapes or forms of separate bodies,
were it not for the force which binds their particles
together.

If, on the other hand, there were no check upon
cohesion, changes of an exactly opposite kind would
come about. The particles of each lesser substance
and of the earth itself would shrink closer and closer
together, till the entire mass would have grown in-
conceivably small and hard.

sentence in a letter of Charles Kingsley’s: ‘Everywhere, skin-

deep below our boasted science, we are brought up short by

mystery impalpable, and by the adamantine gates of transcendental

forces and incomprehensible laws, of which the Lord Who is both

God and Man alone holds the key, and alone can break the seal.’
* Lite of Kingsley,’ ii. 7.



The Weight and State of Air. 29

’ ‘This shrinking and hardening would include the
Ocean of Air. It is what we call ‘repulsion’ among
the air-particles which keeps them apart. If the
particles of any gas are forced closer together by cold
or pressure it becomes a liquid; if they are forced
still closer it changes into a solid. |

‘Probably all earthly substances are capable of
taking these three forms, under certain conditions,
though man has not always means at his command to
work the changes. There are solids which have not
yet been made liquid, and there are gases which remain
persistently gases. For a long while atmospheric air
resisted all efforts; but at length, under intense
pressure and cold, it was liquefied, and even rendered
solid.

So if no force of repulsion existed to counterbalance
the force of cohesion, not only would the whole Earth
become amazingly small and hard, but the whole Ocean
of Air would be transformed into a solid harder than
iron.

It is through the eanodite workings of these two
forces that we have the three forms BF matter—solid,
liquid, and gaseous.

In a solid, the cohesion is said to be eidsiee than
the repulsion. In a liquid, the cohesion and repulsion
are said to be equal. Ina gas, the repulsion is said to
be greater than the cohesion.

The particles of a gas struggle to get far apart one
from another. Unless confined on all sides, they fly
away and are lost. This would happen with our entire
atmosphere if it were not for the controlling power of
gravitation. The Ocean of Airis tied and bound to
earth by gravitation alone. In upper layers, where
both the attraction of the earth and the weight of the



30 The Ocean of Air.

overlying air are lessened, the separate air-particles
float much more widely apart; yet even there, even on
the outermost limits of the atmosphere, they are still
under the restraint of gravitation.

At the level of the sea, the atmosphere presses
upon each square inch of the ground, and of every
creature and thing upon earth, with a weight of about
fifteen pounds. The whole atmosphere all around the
whole earth is said to weigh a great many millions
of millions of tons. So really it is not astonishing
that the lower layers of air should be packed tightly
together.

It seems extraordinary that we do not ourselves fee!
the pressure, since it is upon us as well as upon the
earth. On each square inch of our bodies the atmo-
sphere bears hard with a force of about fifteen pounds’
weight, which means over two thousand pounds upon
the square foot, and something like thirty thousand
pounds upon the whole body of an ordinary-sized
man.

Try to lift a load of one hundred pounds; then
think what it would be to have twenty times that
weight lying upon your chest. You could only expect
to be crushed and killed.

Some such result would doubtless come about, but
for the fact that the pressure exists everywhere. Air
is not only outside but also inside us. It not only
surrounds, but pervades our frames. We, it is true,
are in the air, and no less truly the air is in us.
Pressure from without is counterbalanced by resistance
from within.

This fact of air-pressure can be shown byan ordinary
air-pump. Before the air is pumped out of the beli-



The Weight and State of Air. 31

shaped glass, it may be lifted by a finger; but when
the air is gone from within, the outside air bears
upon it so heavily as to make the glass immovable
under one’s utmost efforts. It is literally jammed down
upon the wooden stand. If the glass were not very
strong, and shaped for resistance, it would be shivered
to pieces.

Atmospheric pressure, acting equally in all direc-
tions, is due to its make asa gas. The particles of a
gas are in a state of ceaseless unrest, for ever hurrying
to and fro one among another with immense speed,
perpetually striking against each other and against the
sides of any vessel in which the gas may be confined.
Each particle of air is always ‘on the rush,’ always
striking and rebounding from its neighbours and any
solid or liquid substances which lie in its path.

If a tumbler is filled to the brim with water, and a
piece of blotting-paper or other soft paper is laid over
it, the glass may be carefully turned upside down, and
the whole body of water will be borne up by the wet
paper. That which keeps the paper in position is
neither more nor less than the ceaseless cannonade of
invisible air-particles—millions of millions of minute
pellets of air banging upwards each instant against the
paper from outside and holding it up.

It is this incessant battery of air-particles which con-
stitutes the pressure of air against the sides of a vessel
—upward, downward, within, without, and all ways. It
is this which, as above stated, when acting inside a
closed box or within the limits of the human frame, is
sufficient completely to counterbalance the outside pres-
sure. It is in this way—through the unceasing hail of
innumerable air-particles on the basin of a barometer—
that the mercury is held up in the barometer-tube.



32 The Ocean of Air.

The same explanation serves also for the rising 0
water in a pump.

Moreover, the degree of pressure varies at different
times and in different places.

A cubic foot of common air near the surface a the
earth generally weighs a little more than an ounce and
a quarter; in other words it generally presses with that
degree of force, not downward only, but in all directions.

Generally: not always.

The degree of pressure is proportional to the number
of air-particles within the cubic foot of air. The more
dense a certain portion of air is—that is to say, the
more closely its particles are packed together—the
heavier its pressure. Thus the weight of the atmo-
sphere generally, caused by gravitation, increases the
density of air near the surface of the Earth, and there-
by increases its pressure.

The amount of pressure is also increased by heat.
If a cubic foot of air is enclosed in a vessel of the same
size and is then heated, the pressure against the top,
bottom and sides of the inside of the vessel becomes
greater, because heat increases the energy of the air-
particles and so adds to the force of their battery.



CHAPTER IV.
AIR AS A MIXTURE.

Tue Air breathed by us and by all living creatures
upon earth is not a simple gas, but a mixture of gases.

Now, there are more ways than one in which
different substances can be mingled together.

You may put a lump of sugar into a cup of tea, and
stir well; the sugar vanishes, yet it is still there.
The separated particles float in the liquid, sweetening
it; though not seen, they may be tasted. No chemical
change has taken place, no real union of two substances
into one. The tea remains tea; the sugar remains
sugar.

Or you may mix together a small quantity of
powdered iron with powdered sulphur. Mixed thus,
they are not united. The iron is iron still; the sulphur
is sulphur still.

But push the mixed powder into a little heap, and
touch it with a lighted match. A red glow will creep
through the whole, and an entirely new black powder
will be the result; formed itself out of the iron and
sulphur, yet in itself neither iron nor sulphur but an
utterly different thing. The iron is gone; the sulphur
is gone ; and something else has sprung into being.

This is chemical change. It is the combining of
two or more separate substances into another and

3



34 The Ocean of Air.

different substance. It is not the mere mixing together
of two substances, which remain still the same that
they were before.

Every substance that we see or know is either Simple:
or Compound. If simple, it consists of one original
substance, which—so far as we at present know—can-
not be broken up into other substances. If compound,
it is formed out of the union of other substances, and
therefore it can by one mode or another be broken up.

Iron is a simple substance. A mass of pure iron
cannot be divided by the chemist into any other sub-
stances. It can be melted into a liquid, and trans-
formed into a gas; but the liquid and the gas are iron
still. Gold is another. It can be melted, and with
enough heat it might be vaporized; but the gold
always remains gold, undergoing no real change.

The chemist can split up or ‘analyze’ many things;
but when he comes to a simple substance, he has
reached a shut door, and can make no further advance.

It would not be safe to assert that all so-called
simple substances are absolutely simple. They may be
compound, though man has not yet discovered the fact.
But in relation to our knowledge they are, at least for
the present, simple.

Water is a compound substance. It is made of
two gases, oxygen and hydrogen The two gases,
separate, are each invisible. When united they are
seen and known as the liquid substance water, the solid
substance ice, the gaseous substance steam or vapour.

Simple Substances are also called Elementary Sub-
stances, or Elements. About sixty-seven are known.
A few among the sixty-seven are enormously abundant;
while others are scarcely ever met with.

They fill much the same place in the world of



Air as a Mixture. 35

matter as the alphabet fills in the world of litera-
ture. All words are made out of the letters of the
alphabet variously put together. All substances are
either simple—that is, they are single letters of the
alphabet—or else they are made up out of the simple
substances variously combined.

The Air of the Atmosphere is a simple mixture of
two simple substances, Nitrogen Gas and Oxygen Gas.

A mixture—not a chemical combination. The two
are mingled together much as tea and sugar are mingled,
floating in close companionship without becoming one.
No change has passed upon the nature of either; and
no third substance is formed. Each gas keeps its own
character.

Oxygen is rather heavier then nitrogen, so one would
expect the oxygen sometimes to sink, the nitrogen to
rise. But this is not the case. Almost invariably, air
is found to be a mixture of the two gases in the same
proportions. No doubt this is more or less due to the
ceaseless movements of air, the perpetual mixing by
winds.

Whether a portion of air is examined from a moun-
tain-top, from a level plain, or from a deep mine,
the mixture is almost exactly the same. Variations
there are, enough to tell upon man’s health, yet they
are at most extremely slight. The amount of nitrogen
in the air is always about four times as much by
measure * as the amount of oxygen.

If one should divide a certain quantity of air into
five almost equal parts, separating the two gases, one
part should be oxygen, four nitrogen.

* By measure, not by weight, since oxygen is the heaviest.
2-2



36 The Ocean of Air.

Or, to put it differently: suppose you have four
gallons of nitrogen gas, and you wish to transform it
into common air. You only have to add one gallon of
oxygen gas, and the thing is done.

Besides the two chief gases of which air is made, a
small quantity of Carbonic Acid Gas, and a still smaller
quantity of Ammonia Gas, are also to be found in it.

If you had ten thousand gallons of air, one fifth of
which would be oxygen, and four-fifths nitrogen: only
about one gallon of carbonic acid gas would be dis-
tributed thinly through the whole. As for ammonia
gas, only one gallon in amount is spread among one
million gallons of air.

So we can hardly speak of these two as having a
large share in the ‘make’ of the atmosphere. They
are rather a slight addition to it, a kind of ‘ flavouring,’
if one may so express it.

Yet carbonic acid gas, despite its comparatively
small amount, is of the greatest possible importance.
And indeed, though the quantity may seem slight,
viewed beside the other gases, it is by no means slight
as a whole. The entire mass of carbonic acid gas
always present in the Ocean of Air is simply enor-
mous.

Besides the gases, there is invariably more or less
water in the atmosphere, hidden away in the form
of Vapour. If you had one thousand gallons of air,
you would find spread through them from four to
sixteen gallons of invisible water-gas, or vapour.

The amount of carbonic acid gas and of water-
vapour is not constant, but varies incessantly at
different times and in different places.

There are also countless specks of matter floating
through the Air-Ocean, especially in its lower regions.



Air as a Mixture. 37

But the amount of these specks I cannot give in gallons.
Probably no one has ever even tried to reckon their
quantity.
We have now found in the air we breathe these

things :

Nitrogen Gas,

Oxygen Gas,

Carbonic Acid Gas,

Ammonia Gas,

Vapour of Water.

Floating Dust.



CHAPTER V.
AIR AS A PART OF EARTH.

Most people know that the Earth is not at rest, but is
in perpetual motion, spinning like a huge top, and also
rushing like an enormous ball round the sun.

I want you now to think steadily about the spinning
movement of Earth—about her daily whirl, top-like,
round and round upon her own axis.

If you stick a knitting-needle through an orange,
and spin the orange upon the knitting-needle, keeping
the needle itself fixed, this will help you to see the
‘ daily rotation’ of earth.

The earth is a huge globe, about eight thousand
miles straight through, from the north to the south
pole, or from the equator on one side to the equator on
the other side.

The movement of Earth’s surface as she spins is
very little indeed near the poles; while on the equator
the surface travels round at the rate of over one thou-
sand miles an hour. A man standing on the equatoris
carried along at that rate always, without the slightest
effort on his own part, borne onward irresistibly by the
rush of the solid ground on which he stands.

But suppose he gets into a balloon and rises into
the air—one, two, three miles upward—what happens
then?



Air as a Part of Earth. 39

Why, then, of course, as thé earth whirls away
from beneath him, he will be left behind, floating in the
still atmosphere. What more simple ?

Well, yes, it sounds very simple—a ‘most natural
answer. There was a time when it would have been
counted entirely correct. Yet the consequences of
such a state of things would be by no means simple.

We know a litile more about the matter now.

Suppose the balloon to start from the Island
Sumatra, exactly on the equator, to the south of Siam.
The solid’ ground there spins’ perpetually round the
centre of’ the earth, at the rate of one thousand miles
an hour.

The balloon rises upward in the calm air, on a still
day, towards the blue tropical sky.

As the surface of the earth below rushes from west
to east at this tremendous speed, more than fourteen
times as fast as the fastest express-train, you would
expect the man in the balloon to be left behind. I do
not mean that he would be blown by winds in any
particular direction, but merely that, as the earth
rushes away, the balloon would be stationary, floating
placidly at rest.

If this were the case, and the balloon‘¢ould remain
undisturbed by currents of air, the man would only
have to float reposefully in the same spot, and in the
course of twenty-four hours the whole circle of the
equator would pass beneath him. He would see in
succession the Indian Ocean, Africa, the Atlantic:
Ocean, South America, the 'Pacific- Ocean, and,. lastly,
the islands from which he started:: “A: wonderful ‘vista
indeed !

But ' practically a man’ in such'a ‘position has no
such magnificent diorama presented to-hims



40 The Ocean of Air.

He rises from Sumatra, and the earth’s surface
is spinning at the rate of one thousand miles an hour
—spinning along, but not spinning away. For as he
rises he looks down upon Sumatra still. If the air
were perfectly breezeless, he might rise to any height
at which he could breathe, and Sumatra still would lie
outspread below. If the wind were easterly, he would
find himself soon looking down on the Indian Ocean.
If the wind were westerly, he would travel towards the
Pacific Ocean.

The explanation lies in the fact that the atmo-
sphere is attached to the earth and whirls with the
earth.

Air, remember, is a material substance, not solid,
but formed of particles of matter. It is held fast to
earth by the force of gravitation. Each particle of air
has its share in the motion of the solid body to which
it belongs, to which it is tied by its own weight, that
weight being due to gravitation. Earth and Atmo-
sphere are practically one, and they act as one in the
daily whirl.

I do not say that there is no lagging behind of upper
layers of air anywhere upon earth. But taking the
matter generally, the entire atmosphere spins with the
spinning earth. The air in any one part has precisely
the same motion as the ground on or near which it
rests.

So a balloon or a bird in the air is carried with the
air in its daily rush around earth’s axis.

Imagine what the results would be if things were
otherwise, if the air remained fixed, while the surface
of the earth whirled away beneath.

We all know the effects of a high wind or a
hurricane. Now, wind is simply air in motion.



Air as a Part of Earth. 4I

If the air were utterly at rest, you may say that at
all events we could then have no wind.

But the effects of wind may be brought about in
two ways. One way is by the motion of air against
still objects; the other is by the motion of objects
through still air. Whether the air rushes fast against
a man, or whether a man rushes fast through the air,
makes no real difference. In either case the effect is
the same; in either case he is struck with the same
degree of force, by the resisting particles of air.

If the atmosphere were at rest, there would perhaps
not be a wind, strictly speaking. Nevertheless, if you
on the equator were careering at the rate of one
thousand miles an hour through still air, the effects
upon yourself would be precisely the same as if you
were at rest, and the wind were careering past you at
that rate.

A powerful hurricane travels at the rate of ninety
miles or more an hour, and the most solid buildings
often cannot stand against it. The heavy pressure of
air-particles, crowding one upon another in their frantic
rush, will level massive walls, tear off roofs, lay trees flat.

You may suppose, then, the destruction that would
be wrought by a hurricane blowing, not at the rate of
ninety milcs, but of one thousand miles an hour. The
results must prove equally overwhelming, whether
caused by the rush of air past us or by our rush through
the air; for in either case the fierce resistance of air-
particles would be the same.

A man standing on an engine going at the rate of
sixty miles an hour has a powerful wind in his face.
The air may be entirely still, no breeze stirring it, yet
his steady advance among the motionless air-particles
will cause him to have exactly the same sensations as



42 The Ocean of Air.

if he were at rest and a-strong gale were blowing.
To all intents and purposes it is a gale. The pressure
of air, resisting his passage, is in no whit different,
whether iis movement or its movement be the cause.

In the case that we have supposed of the solid
earth revolving while the atmosphere above remains at
rest, the resistance of the air in equatorial regions
would be tremendous, past imagination. Nothing
loose or movable on earth’s surface could stand.
against it.

Men and animals, trees and buildings, rocks and
stones, boats and ships—nay, the whole mass of ocean-
water itself—would be kept back by the enormous
pressure of the atmosphere, acting as a terrific hurri-
cane, and would be swept in one rushing pell-mell
torrent of ruin over the revolving surface of earth, in
the contrary direction to earth’s whirl. Complete
chaos and destruction could alone ensue.

This widespread destruction is prevented by the
simple fact that, as Earth whirls, her enfolding vesture
of air whirls with her. Practically, indeed, things not
only are so, but must be so. The atmosphere, weighted
by gravitation, clinging to earth, must move with the
earth. That the earth should revolve and the atmo-
sphere not revolve is an impossibility. The layer of air
lying close to earth’s surface is dragged round by the
earth, and drags round the layer above, which in its
turn does the same for the next, and so on, upward.
Or, rather, if the atmosphere were by any possibility at
rest, it would in this manner be speedily set going.
Once made to revolve, it is certain to go on revolving
until stopped by some other force.

Yet so calm, so soft, so steady is the motion,
despite its great speed, that we upon earth, carried.



Air as a@ Part of Earth. 43

smoothly along by the solid ground and the elastic* air,
are not conscious of it by sensation.

This same partaking of the motion of another body
may be seen on a smaller scale in common life.

Suppose a ship to be sailing over the sea, and a
man standing on the deck. That man is borne onward
by no exertion of his own. He remains perfectly still;
he makes no effort to advance. With relation to the
ship, though not with relation to the sea, he is at rest.
He does move, but only as a part of the ship, as sharer
in the ship’s motion.

A man seated in a train has a motion in common
with the train. As the train travels so he travels; and
so the air in the closed compartment travels. Outside,
the particles of still air strike the moving train with
sharp resistance; inside, both air and man are borne
along as part of the train.

The resistance of air-particles to any body passing
among them may appear a slight matter ; yet it works
a weighty part in the affairs of this world, not to speak
of other worlds, where also enfolding atmospheres
exist.

* Airis not only an elastic but also a viscous substance. An
elastic body yields for the moment to force, and springs back to its
original form when the force ceases to act. A viscous body yields
slowly to long-continued force ; but having yielded it retains its
new shape permanently ; and so long as the force continues to act,
it continues more and more to alter. Viscosity in a body implies a
certain amount of steady resistance to strain or pressure, with
gradual yielding to it, and lasting change of form in consequence.

There is some amount of elasticity in Air, and some amount of
viscosity also,



CHAPTER VI.
THE RESISTANCE OF AIR.

IF you draw your hand quickly through water you are
aware of a counter-pressure; the water seems trying
to hinder or push it back. A man swimming in the
sea or rowing a boat is keenly conscious of this.

The same resistance, though not to the same extent,
is found in the Ocean of Air. The particles of a gasare
less densely placed, less close together, than those of a
liquid; therefore a body moving in their midst can more
easily thrust them aside to make way for itself. Still,
there always is a measure of resistance.

This fact of Air-resistance is a serious item for con-
sideration in the matter of motion generally.

There are many bodies on earth at rest, and many
in motion. Those at rest have usually to move sooner
or later; those in motion come, as a rule, sooner or
later to rest. Two main rules govern the condition of
objects in motion or at rest. One is well known, the
other not so well known. They are these:

I. A body at rest is never set in motion except by
force.

II. A body in motion is never brought to rest except
by force. ,

The first of the two everybody will assent to at
once. We all know that a ball does not set itself



The Resistance of Air. 45

rolling; that a train will not start itself; that a cannon
cannot fire itself off. A certain amount of power or
force must be exerted upon a body from outside to
make it move, and it must always be enough force to
cause the particular movement required. A man’s
hand can throw or roll a ball of india-rubber, but a
man’s hand cannot start a train.

Even in the case of a man walking, though in a
sense he does set himself going, yet this only means
that his will takes the place of the outside force, and
causes his muscles to act.

But to say that a body in motion can only be
stopped by force—that is another matter !

Do we not all know that nothing on earth continues
moving for ever? Do we not all know that everything
inevitably stops sooner or later? Have we not seen
for ourselves how the swift cannon-ball, the whirling
grindstone, the spinning-top, the swinging pendulum, all
come to repose? Did not our ancestors search in vain
for ‘ perpetual motion,’ wasting time and money in a
hopeless quest, because no motion of bodies on earth
ever is perpetual ?

Yes, true enough, all this. Yet none the less true is
the rule given: motion is never stopped but by force.
No single body will ever move unless it is made to
move. Once set going it will never cease moving,
unless it is brought to rest by the exercise of a counter-
force.

For motion is as naturally permanent as rest!

Rather difficult to believe—is it nct ? Yet this is a
fundamental fact.

You see a big rock lying on a mountain-side, and
you are quite ready to assent, when somebody remarks
that the rock will not stir without being made to do so



46 The Ocean of Air.

There is a certain reluctance to change its present
condition, a stubbornness or inertia about the rock.
This inertia chains it to the spot where it lies, until
some outside force shall be exerted to set it
going.

But suppose such a force is exerted, and the great
rock is sent rolling, leaping, crashing, fiercely down the
steep mountain-side.

We have now a new state of things. The rock is
no longer at rest; it is in motion. The stubbornness,
the reluctance to change its present state, a state of
motion—the inertia, in short, of the rock—continue
as before, though manifested differently. Then the
rock was at rest, and it would not move without being
made to move. Now the rock is in motion, and it will
not stop without being made to stop.

Not stop! You are hardly so ready to assent to
this as to the former statement. Of course it will
stop, So soon as it reaches level ground!

Yes, of course. Concussion with the level ground
will prove to be a sufficient checking force. I did not
say that the rock would never cease to move. I only
said that it would not stop without the exercise of
force. No doubt a sufficient force will be exercised by
the resisting ground.

In this world there always is a sufficient checking
force to bring all moving bodies to rest. That fact
does not in the least detract from the truth of the _
opposite fact that, if no checking force existed, the
body would not cease to move. .

Take a tennis-ball in your hand, and fling it high.
That tennis-ball will go on for ever, unless stopped.

Fire a bullet from a rifle. That bullet will speed
onward for ever, unless stopped.



The. Resistance of Air. 47

Set a. grindstone whirling fast. That grindstone
will whirl for ever, unless stopped.

Make a top spin steadily. That top will spin for
ever, unless stopped.

These things always are stopped. But they do
not stop themselves; they do not come to rest of
themselves. Always, invariably, sufficient force is used
by something or somebody to bring them to a state of
repose. ;

The great checks to continued movement on earth
are commonly reckoned as two—Friction and the
Resistance of the Air. ;

These two may almost be reduced to one; for the
resistance of the air is really only a delicate form of
friction. It means simply the striking and rubbing of
the tiny particles of air against anything passing
through the midst of them.

The attraction of the earth is another great
hindrance to motion, but this also comes under the
head of friction. The earth draws the moving or
falling body downward; then friction against the
ground, rocks, or water, causes it to stop.

So by friction we mean the touching and rubbing
of other substances. If you touch a spinning top
ever so lightly with your finger, you will see at once
how great is the checking power of a touch to anything
in motion. Asa rule the word is used with reference
to solid bodies; but the resistance of water-particles
and air-particles practically amounts to the same
thing.

A great cannon-ball is despatched from the mouth
of a huge cannon, whizzing, whirling, tearing along,
ready to destroy aught that may lie in its path. The



48 The Ocean of Air.

force which has started the ball is the gunpowder
explosion, the sudden change of a solid into a gaseous
form, and the consequent tremendous pressure of
gaseous particles fighting to escape, thus overcoming
utterly the stubborn inertia of the ball at rest.

But when once the ball is off, some other force,
equal in degree, is needed to overcome the stubborn
inertia of the ball in motion, before it can be brought
to rest once more. Only, instead of being a single
sharp exercise of power, pent up in a tiny space and
in one moment, it may be a slow and continued
exercise of force, gradually acting.

If no such force is exerted, the ball will rush on
for ever, always in a straight line, always at the same
speed.

First the air-particles begin. It is wonderful to
think that such weak floating infinitesimal specks of
matter can have the smallest effect upon a mighty
cannon-ball. Perhaps you have never been underneath
a cannon-ball fired from a large gun, and so have not
heard the furious rush and whiz of its passage among
those air-particles, sounding like a small express-train
careering over your head. If you had, you would
realize that the opposition which they offer is by no
means contemptible. Singly they are soft and weak,
but banded together, acting in concert, they are
strong.

From the moment that the ball leaves the cannon .
they are at work. Each air-particle which lies in the
path of the ball, only to be fiercely thrust aside, only
to seem an utter failure, has done its tiny task. The
air-particles alone, unaided, would in time bring the
great ball to rest.

But something else is at work also, in conjunction



The Resistance of Air. 49

with the struggling particles of air. Earth is drag-
ging at the ball with her ceaseless pull. The force
of the explosion may send it far upward, yet soon the
pull of Earth tells, and a downward curve begins which
presently lands the ball upon the ground. For awhile
still it may leap and bound forward, but with every
crash of contact a further check is given, and at length
the moving body is at rest.

Yet, remember—the cannon-ball would never of
itself have travelled in a curved path or with slacken-
ing speed. It would have gone on interminably,
always straight forward, always at the same speed.
Without the resistance of the air, the attraction of the
earth, and the friction of the ground, it would not
have stopped.

So there was a sufficient cause for the starting of
the cannon-ball; there was a sufficient cause for its
moving in a bent path; there was a sufficient cause
for its going more slowly; there was a sufficient cause
for its coming to a standstill.

There is always a sufficient cause for every move-
ment, and for every change of movement, in a moving
body, just as much as for any movement at all in a
body hitherto at rest.

We thus see distinctly that it was the inertia of the
heavy cannon-ball which made a strong explosive force
needful to start it in swift career. Once started, it was
the very same inertia, differently shown, which made
the continued resistance of air and earth needful to
bring it to repose.

A curious calculation has been made illustrating
how great is the resistance of air-particles to a body
moving with great rapidity. A cannon-ball is fired off,
and travels, let us say, some six thousand feet before

4



50 The Ocean of Ain

touching the ground. If the air offered no resistance,
it would have sped to a distance of over twenty thou-
sand feet in one unbroken rush.*

The nearest approach to unceasing motion on earth
is to be found in a pendulum, hung in a vacuum from a
hard fine point. There, no soft elastic atmosphere
checks the steady swing. Nothing checks it, except a
very slight degree of friction at the point from which it
hangs. Still, some amount of rubbing always does
and must exist at that point. The pendulum may
swing for hours, even through a whole day, but sooner
or later it has to stop.

The only apparently perpetual motion, of which we
can speak with confidence, is that of the heavenly
bodies—the whirling and revolving suns and worlds.

Our Earth is one of those worlds. Her movements
have lasted through ages unchanged, since the Hand
of God sent her forth upon her celestial pathway.

How she was first set going we do not know; and
how long she will continue to move we do not know.
All we know is that sufficient force must have been
exerted to set her whirling and revolving; and that
no sufficient force has ever since been exerted to bring
her to a standstill.

In the wide regions of space no air exists to check
her movements. The Earth carries the Atmosphere
with her as she rolls onward; a soft surrounding
vesture; a deep translucent ocean; a very part of
herself. There is no vast Ocean of Air throughout
space. The stars and planets roll unhindered through
centuries of centuries, with calm continuous whirl.

Something, indeed, there probably is, though not
air, something unspeakably thinner and lighter than

* Todhunter.



The Resistance of Air. 51

our atmosphere, something so rare and fine that we
can scarcely more than guess at its existence. But if
this ‘something,’ which we call ‘ther,’ does indeed
extend through space, and can exercise any checking
force upon the heavenly bodies, it is a force so slight,
so slow in action, that no results are yet apparent. To
man, watching with dim eyes from the lower levels
of the Air-Ocean, the motions of suns and worlds
through thousands of years show no change.






PART II.
GASES OF THE AIR-OCEAN,







CHAPTER VII.
THE USES OF OXYGEN.

WE must now learn a little more about the separate
Gases which, mixed together, make our Ocean of Air.

Wherever Atmospheric Air is found, it consists, as
explained earlier, of about four-fifths by measure of
nitrogen to one of oxygen. Though the quantity of
nitrogen is so much greater than that of oxygen, yet
the oxygen may well claim our chief attention.

Oxygen is the great Life-supporting power on earth.
Without oxygen, plants could not grow. Without
oxygen, animals could not exist. Also, without oxygen,
fire could not burn. Nitrogen does little positive work
in comparison, but rather fills the humble office of a
make-weight and a drag upon the intense activity of
its companion.

One of the compounds of nitrogen, from which,
indeed, comes its name, is nitre. Another is nitrous
oxide, well known under its old name of ‘ laughing gas.’
If breathed under particular conditions it causes a
kind of intoxication, and when in that state men act in
a strange and laughable manner. It is now much used
by dentists, and also by surgeons in smaller surgical
cases for the deadening of pain. As its name tells, it
is formed of nitrogen and oxygen.

Nitrogen is found in the solid earth, as well as



56 . The Ocean of Air.

in the Ocean of Air. It has a share in the make of
plants and animals; no unimportant share in the case
of animals, for without nitrogen neither blood nor
muscle could be formed.

Pure nitrogen is colourless, tasteless, and scentless.
It is called ‘ inert,’ or slow and heavy, from its seeming
reluctance to unite with other substances. It does
unite with some, but not readily. Oxygen, on the
other hand, seems always to hold itself open to com-
bine as fast as possible with almost any other substance.

One might liken those two gases, with their very
opposite characteristics, to two opposite characters
often seen in men—the first, dull, slow, holding aloof
from other people, cautious and cold, rarely making
friends; the second, eager, sparkling, warm-hearted,
prepared to rush into enthusiastic friendship with
nearly anybody who may come in his way.

Nor is it difficult to understand how, if these two
lived and worked together, the slowness, caution, and
coldness of the one would act as a check upon the
eagerness of his impulsive companion,—just as nitrogen
does upon oxygen.

Suppose you have two closed jars, one full of pure
nitrogen gas, the other full of pure oxygen gas; and
also a little wax candle, like those which are used for
Christmas trees.

If you light the candle and lower it into the
nitrogen gas, not letting the gas escape and not letting
any air get in, the flame will at once go out. Butif you
put the lighted candle into the jar of oxygen gas, it
will burn much more quickly and brightly than in
common air.

Nitrogen gas cannot support combustion. In
common air oxygen does all that work, and nitrogen



The Uses of Oxygen.

Cae

7
only hinders it. Pure oxygen, apart from nitrogen, is
a tremendous quickener of fire.

Suppose, instead of putting a lighted candle into
either of the closed jars, you were to put a poor little
mouse into each? Jam not advising this act, for if
needless it would be cruel; but suppose it had to be
done.

The mouse in the nitrogen would quickly die of
suffocation. He would not be poisoned, for, strictly
speaking, nitrogen is not poisonous. The little creature
would simply die from lack of oxygen—would die
because the nitrogen is dull and powerless to do for
his little frame what is needed to keep it going.
Nitrogen can no more support life than it can support
fire.

The mouse placed in pure oxygen would not be
suffocated, but it too would die, though not so quickly,
of the too strong oxygen.

We all know the effects of a very strong pure alr—
that is, air which has rather more than the usual
quantity of oxygen. It excites and exhilarates the
whole frame.

To breathe perfectly pure oxygen for any length of
time would have the same effect, but in a very intense
degree. It would be an extreme case of what is called
‘over-stimulation.’ If our atmosphere could get rid of
all its nitrogen, ard consist of oxygen alone, the whole
of mankind would be speedily laid low or driven mad
with desperate fevers, burning away their strength.
And if any building in a town caught fire, the whole
town would be doomed, the flames spreading with such
ruthless fury that all efforts to check them would be in
vain.

Thus we find the need of the dull deadening nitrogen



58 The Ocean of Air.

to control the too exciting oxygen. The oxygen has,
in fact, to be weakened for our use, just as many a
strong medicine has to be diluted with water before
we can safely drink it.

Nitrogen gas has been changed by chemists to a
liquid, and even to a solid, described as ‘a snow-like
crystalline mass.’ Oxygen gas, also, has been liquefied,
and is capable of becoming a solid—in other words, of
being frozen. Both these are always gases on earth
in their natural state, great cold or great pressure
being needed to change their state. When either is
combined, however, with other substances, the result
is often a liquid or a solid.

Like nitrogen gas, oxygen is colourless, invisible,
tasteless and scentless.

There are enormous quantities of oxygen on Earth,
apart from what is constantly floating free in the Ocean
of Air.

The rocks of earth, piled often to mountainous
heights, are in their make, nearly one-half oxygen, by
weight. The stones, big and little, which lie scattered
by millions on earth’s surface, are in their make nearly
one-half oxygen by weight. The soils of earth, from
which sprout grasses, plants, and trees, are in their
make nearly one-half oxygen by weight. The waters.of
Earth—seas and rivers, ice-fields, clouds and vapour—
are in their make not only one-half, but eight-ninths,
oxygen by weight. And when we come to examine
the bodies of living things, both plants and animals,
we find them also to contain in their make a goodly
amount of oxygen.

In fact, if the whole of our solid globe were broken
up into all its ‘component parts’—that is, into the
separate substances of which it is composed—each



The Uses of Oxygen. 59

different substance being placed alone—the heaviest
supply of all would be the oxygen supply. Nearly one-
half, by weight, of the entire mass would be. pure
oxygen.

I say distinctly ‘by weight,’ and not ‘in size.’
Oxygen might be far the heaviest heap without being
the biggest. Many light substances take up more room
than heavy ones.

If you have a gallon of water, that water has in its
make eight times as much oxygen as hydrogen by
weight ; yet if the water is divided into the two gases,
it will be found that the hydrogen takes twice as much
room, or is twice as large, as the oxygen; for hydrogen
is light, and oxygen is heavy.

So we see that oxygen is one of the most important
elements on earth, and also that we have a very large
supply of it.

But if questioned what oxygen really is, 1 can omy
answer that it is, or appears to be, a simple substance.
It will unite with or separate from other substances;
yet in itself it remains unchanged. It can never be
broken up into other substances. Seeking to analyze
the make of oxygen, we come to one of those fast-shut
doors spoken of earlier. ‘Thus far,’ seems to be
uttered, and we can go no farther.

By-and-by, it is true, science may find a mode of
opening that closed door and getting through. If so,
the mystery will only be pushed a little farther back.
Another closed door is sure to lie not far behind. This
is always the case. With our present powers we never
do or can get to the end of anything, with no mystery
lying beyond. One might almost say that, if we could,
that would be the greatest mystery of all.



60 The Ocean of Air.

At present oxygen is—as to its real nature—a
shut door. We know of its existence; we see what it
does, and what it cannot do; we are acquainted with its
peculiar characteristics, its especial modes of action;
we are aware what to expect from oxygen in particular
circumstances. That is about all.

Oxygen is by no means stationary, fixed in certain
positions through countless ages. Portions of oxygen
may remain very long fixed in such solid bodies as
rocks and stones, though even they are subject to
waste. But oxygen in general is remarkable for its
activity, its love of change.

A perpetual intercourse is kept up between the
oxygen of the earth, of the sea, and of the air ; between
the oxygen of living creatures and of things without life.

Oxygen is for ever passing into structures and out

of them again; becoming part of organisms and leaving
them ; uniting with other elements, and breaking loose
from them; entering into the make of liquids, only to
separate itself anew; feeding flame, and life, and
_growth, but in the very act finding renewed freedom;
ready always to be, caught and ‘fixed’ by the next
substance which may come in its way under the right
conditions, yet seldom content to stay long in any
combination where escape is possible. Thus a cease-
less Circulation of Oxygen is kept up.

There are other circulation systems to be noticed
later. There is the Circulation of Blood in a living
animal; there is the Circulation of Air; there is the
Circulation of Water. But this Circulation of Oxygen
is not the least remarkable among them.

Almost all substances will unite with oxygen to
form fresh substances. These others, springing from



The Uses of Oxygen. 61

the union, are called Oxides, and the act of combining
is called Oxidation.

To cause such union, a certain amount of heat
must be brought to bear upon the different sub-
stances, and not always the same amount. Some
substances require more, some less, before they will
unite.

Whenever chemical combination takes place, under
the influence of heat, there is also a giving-off of heat
by the bodies as they unite.

This is an invariable rule, though the heat may not
always be felt or seen by us.

If the union takes place very slowly, as in the
forming of iron-rust, the heat given out will be gentle
and imperceptible. If the union takes place: fast,
as in the burning of a piece of wood, there will be
sensible warmth and a red glow, perhaps flame. If
the union takes place with extreme suddenness, as in
a gunpowder explosion, there will be great heat, a
bright flash of flame, and a loud noise.



CHAPTER VIII.
WHAT IS MEANT BY BURNING?

SOMETHING is meant by Burning which has a great deal
to do with the Ocean of Air around us. For if there
were no air, there could be no Combustion.

On a cold winter’s day we have a fire in the sitting-
room. The flames play about the coal, and gradually
the lumps of coal grow smaller, till they disappear. If
more coal is not heaped on in time, the fire goes
out.

What becomes of the coal ?

It is burnt, of course. Any child could answer that
question.

But what does ‘ being burnt’ mean?

Suppose we have an iron ball in the grate, lying
among the burning coals, to fill up some of the space.
This ball gets red-hot, like the coals, though it does
not, like them, send out flames. Heat is very ‘ catch-
ing,’ and passes readily from one object to another.

The iron ball seems to burn, like the coals; yet,
unlike the coals, it shows no tendency to disappear.
It does not even get perceptibly smaller. When the
fire dies out and the red-hot ball grows cool, it is seen
to be unchanged.

If the one burns and vanishes, why does the other
burn and not vanish ?



What is meant by Burning ? 63

This question is easily answered. The iron ball
does not burn. Some substances burn easily, and some
not easily. Some will burn at any time in common
air, and some only under particular circumstances.

Iron is a substance which will ‘stand fire.’ It can
be made red-hot or white-hot, melted, and even turned
into a gas; but it will not burn in common air.

So becoming red-hot or white-hot is not necessarily
the same as burning.

But though iron will not burn in air, it can be made
to burn—really to burn, lessen in size, and disappear—
like wood. If a piece of iron-wire is placed in a vessel
filled with pure oxygen gas, it can be set alight, and will
burn away as easily as a wooden match.

In the end of the last chapter I spoke of fast and
slow combining, and mentioned iron-rust as an example
of the slow combining.

Now, iron-rust simply comes from the union of iron
with oxygen—generally at a slow rate in a damp place
—and it is called Oxide of Iron.

But this same oxide of iron, or iron rust, can also
be produced quickly by burning a piece of iron in
oxygen gas, as above described. Then, again, the iron
unites with oxygen, and iron oxide, or rust, is formed.
Only, as the union takes place fast, much more heat is
given forth in a few seconds. The more rapidly heat is
sent out in burning, the more intense it is.

Whether the rust is formed fast or slowly, the
actual process is the same. It is Oxidation. We call
the one a case of ‘burning,’ and not the other; yet
the only real difference between the two is in respect
of temperature and speed. The common trusting of
iron in a damp place really is a species of very slow and
languid combustion.



64 The Ocean of Arr.

What becomes of the coal in the grate when it
burns and diminishes in size ?

The coal is divided, and goes three ways. Part
rises up the chimney as smoke or soot. Part falls
below as ashes. Part unites invisibly with oxygen
from the air, causing heat and flame in the act of union.

You have seen that iron can unite quickly with
oxygen by burning, as we usually understand the term,
only when it has to do with pure oxygen, unweakened
by nitrogen. But coal or wood, when sufficiently
heated, can take the oxygen out of the air, leaving
the nitrogen behind. So we say that they ‘burn
easily.’

If the fire has been allowed to get too low, and
fresh coal put on will not ‘catch,’ what then? Why,
then we use the bellows, and pour a supply of fresh air
in gentle streams upon the reddest spot remaining, in
the hope that a new and abundant supply of oxygen
gas will waken the half-dead embers and revive the
flame. The oxygen gas in the air lying close to the
coals has been pretty well used up, but a fresh supply
will give what is needed.

Coal alone, without oxygen gas, cannot give us
flame and heat. For oxygen is the great quickener
and supporter of fire.

If we could banish all the oxygen gas from the
room, keeping only nitrogen gas, any amount of paper,
wood, and coal might be put into the grate, and the
bellows might be used to any extent, yet to no avail.
The fire would at once die out. Nitrogen is powerless
to keep it alive.

So now we see the object of bellows to waken a

dying fire—just that a fresh supply of the needful
oxygen may be given.



What is meant by Burning ? 65

‘Wisdom is profitable to direct,’ saith the wisest
of kings. One cannot but remember these words,
when watching an uneducated maid puffing away at
a lump of black coal, without the slightest result. A
very little wisdom would teach her to direct the stream
of fresh air towards a ved spot, where alone it can take
effect.

If bellows could be so made as to feed the fire with
pure oxygen gas, then at any time the last spark of a
dying ember might be roused with ease into fresh
life.

Such bellows would also have a curious effect on
the red-hot iron ball. Under a steady play of oxygen
gas, the ball would begin to waste away like burning
coal.

When anything ‘burns,’ it not only gets red-hot, but
also there is a rapid loss of material. It grows smaller
and smaller, and almost or quite disappears. Either
part or the whole of its substance unites with the
oxygen of the air, and passes out of sight into the
atmosphere.

This is what we mean by a body ‘ burning,’ or being
‘in combustion.’

To make a body red-hot is enough often for com-
bustion, without flames. Where inflammable gas
exists—that is, a gas which will unite quickly with
oxygen—there will be flame. Usually, flame arises,
not from a solid or a liquid but from a gas in combus-
tion. When flames play round a burning lump of coal,
they are caused by the escaping hydrogen. Some sub-
stances will only grow red-hot and waste, but will not
show flame.

Any body intensely heated and glowing, yet not
lessening in size, losing weight, or uniting with oxygen,

5



66 The Ocean of Atr.

does not burn. The heated object is then said to be
‘ignited,’ or ‘incandescent,’ but not ‘in combustion.’

If a piece of magnesium wire is held in the flame of
a gas-burner it will take fire, burn brightly, and waste
away, growing shorter.

If a piece of coiled platinum wire is held in the
flame it will become hot and glow brightly, but there
will be no perceptible loss of material.

So the magnesium wire is said to be ‘in com-
bustion ;’ the platinum wire is said to be ‘in a state of
* incandescence.’

We see an instance of the latter in many of the
new electric lamps. A thread of carbon is shut up in
a glass bulb from which all air has been expelled, and
it is then made red or white hot by a stream of elec-
tricity. But it does not burn; it only glows. It
cannot burn, for there is no oxygen within reach, and
the ‘burning’ of a substance means its union with
oxygen.

Another instance is known to us in the glowing
gases which play fiercely over the sun. In common
speech we talk of the ‘burning’ surface of the sun;
yet the term is wrong. The gases which send out so
intense a glare are, it is believed, only glowing, not
burning. They give forth heat and light, but they do
not unite with oxygen and waste away. To speak of
flames on the sun is equally incorrect. Flame is gas
in combustion, and the gases of the sun are believed
to be only incandescent, not in combustion.

For true burning the presence of oxygen is generally
needful, and the presence of some other combustible
substance to combine with the oxygen is equally needful.

We can no more make a fire of oxygen without



What is meant by Burning ? 67°

coal than of coal without oxygen, for both are required.
Having both, we must bring them together, and must
place them under the touch of sufficient heat. When
this is done, and the union of the two is started, enough
heat will be given out for carrying on the work and for
warming the room.

In the lighting of an ordinary fire, heat is first ap-
plied by a lighted match to the paper or shavings.
Some of the paper or shaving substance at once unites
with a little oxygen in the air, and that act—the
breaking loose of particles from the solid substance to
join with particles of oxygen—causes a setting free of
fresh heat. This heat spreads to the wood, and another
union then takes place, particles of wood breaking
loose to form a combination with more oxygen.
Further heat is again given out, which spreads to the
coal, which in its turn catches fire, entering on a course
of union with the ever-ready oxygen. Thus heat both
causes and springs from combustion. Now, what of
the new substances formed by these various’ com-
binations ? é

The particular substance which is formed must de-
pend in each case upon the particular substance which
is burnt. As a matter of fact, in the common every-
day burnings around us, two especial substances are
by far the most common as the ‘second party’ in this
union. They are—Carbon and Hydrogen.

When a lump of coal is burnt, part goes up the
chimney as soot, part falls below as white ash, part
vanishes. So with the burning of a wax candle: part
passes away as soot, while the greater part slowly
disappears.

Yet, though the coal and the wax pass out of our

5—2



68 The Ocean of Air.

sight, their substance is not destroyed. So far as we
can tell, no matter once created is ever put out of
existence. "We cannot say that it never will be, for the
future of the Universe of Matter is utterly unknown to
us. But man has no power to destroy a particle of it.

True, he can by using the Forces of Nature break
up many materials, change their form, cause them to
vanish. Yet the vanished particles may reappear.
The old form may be restored. There is no real de-
struction of the tiniest atom.

In the case of burning coal or wax, each particle
exists still, afterwards, somewhere and in some shape.

Part of the coal drops below as white ash. This
is the mineral- substance which cannot burn. Part
escapes as soot, or unburnt carbon. The great mass
of the carbon, which is the chief portion of the coal,
unites itself with oxygen, and forms a new combination.
This new combination, called Carbonic Acid Gas, floats
away, invisible, joining the hot smoke in its passage up
the chimney. Meanwhile the hydrogen gas, held in
the coal, also joins itself to oxygen, causing bright
flames as it does so. The result of that union is-—
Water, in the form of vapour.

The same takes place in the burning of a cande.
Some of the carbon escapes as unburnt soot, while the
greater part unites itself to oxygen, and those two,
losing their separate individuality, pass away into the
air as carbonic acid gas. The hydrogen combines
with surrounding oxygen, and these also float off as
invisible vapour of water.

If a clear cold tumbler is held over a candle-flame
it will grow dim with fine moisture. This moisture is
some of the newly-made water, condensed into a tiny
dew by the chill of the glass.



What is meant by Burning ? 69

The bright light given out by a candle or gas flame
springs mainly from the glowing of fine carbon-points
which float within the flame. Whereany of the carbon
is within touch of the air, it unites with oxygen and goes
off as carbonic acid. Inside the body of the flame the
air has no access, and there the carbon-specks can only
glow. For lack of oxygen they cannot burn, and so
they pass away as smoke.

If the whole of the carbon contained in the wax
could be at once burnt up as the flame creeps down
the wick, there would be no smoke and very little light,
but there would be much more heat.

Hundreds of tons of coal are daily consumed in
every great English city, especially in winter. It is
a wonderful fact, if we consider what is meant by
‘burning.’ A mighty mass of solid black coal is in
twenty-four hours utterly disposed of by the soft
translucent air, not swept aside in one mighty hurri-
cane blast, but gently lifted particle by particle, carried
off, and hidden away by the busy oxygen.



CHAPTER IX.
THREE FORMS OF CARBON.

BEFORE going into the carbonic acid gas of the Atmo-
sphere, we must think a little about Carbon, from the
union of which with oxygen springs carbonic acid.

Carbon is another simple substance—another of
those mysterious shut doors, beyond which, at present,
we cannot pass. It cannot by any means yet dis-
covered be split up or divided into other substances.

We have had so far to do with simple substances,
which in their ordinary free state on earth are gases,
such as nitrogen and oxygen.

Carbon in its natural earthly state is a solid, and
not only so, but it is one of the most stubborn solids
known. For a long while it resisted all attempts to
thaw it into a liquid.

When united with other substances, carbon appears
in multifarious forms, the names of which are legion.
It is a most abundant material, and it enters enormously
into the make of all vegetable and animal bodies—of
all ‘organized’ bodies, or creatures with life.

Without carbon our earth would be an uninhabited
desert. Without carbon we should have no grass, no
plants, no corn, no trees. Without carbon we should
have no birds or beasts. Without carbon there could
be no men, as now constituted.



Three Forms of Carbon. 71

For ‘men are built up of carbon !’—of course, with
the addition of other ingredients. In charred wood,
charred meat, charred human flesh, the underlying
black carbon is plainly to be seen. If the wood, meat,
or flesh is entirely burnt up, then no carbon remains:
the whole has united with oxygen, and has vanished as
carbonic acid gas.

White loaf-sugar is a Compound Substance, being
formed of carbon and water, for sugar is a vegetable
product. If sulphuric acid or oil of vitriol is poured
upon thick sugar-syrup, the mass blackens and swells
upward into a large quantity of loose charcoal.

Carbon is abundant in many rocks, such as marble
and limestone; also in chalk, coral, and shells, which
are largely of animal make. But while all this
is true—while numberless forms of vegetable and
animal substance are composed in a great measure of
carbon—yet in its most pure form, free from combina-
tion with other substances, carbon appears mainly in
three distinct characters.

The first form of pure carbon is CHARCOAL.

Perfectly pure charcoal is not common, any more
than perfectly pure aught else in this world. Every-
thing gets mixed up more or less with other things;
but if wood is slowly burnt in a vessel nearly closed,
tolerably pure charcoal will remain.

A far more important form of carbon, very nearly
allied to wood-charcoal, though less pure, is COAL.

What the world would be without coal, we can
only imagine by looking back in fancy to those times
when coal had not been discovered. All modern life,
modern comforts, modern appliances, modern dis-
coveries, modern experiments and inventions, seem to



72 The Ocean of Air.

depend upon the existence of coal. Without coal,
unless something else should take its place, England
would sink back into a kind of semi-barbarism.

Coal is a form of carbon. It is made from wood,
which consists largely of carbon, since trees, like men,
are very much built up of carbon.

Coal-fields are the buried remains of mighty ancient
forests, and the structure of wood can often be traced
in a piece of coal.

But this structure has generally vanished; for a
change has passed over. the woody substance, trans-
forming it into the fossil substance called coal.

The change has been brought about by an under-
ground operation, which is in fact much the same as
that by which a log of wood is transformed into char-
coal, only in the one case the action has been very slow,
in the other it is quick. The transformation of those
buried forests into not very pure charcoal has really
been through a course of exceedingly slow combustion
or oxidation, spread out over ages. Coal is the charred
remains of a former vegetation.

Combustion, as we have seen, does not always
mean becoming red-hot; though it always means
some amount of union with oxygen.

Is it not wonderful that all this preparation of fuel
was going on through long ages, man never dreaming
of any such merciful provision for the future of his
race ?

So charcoal, coke, or coal, is one form of carbon in
its natural state.

The second form of pure or nearly pure carbon is
GRAPHITE or PLUMBAGO,
We all know graphite as blacklead—wrongly so



Three Forms of Carbon. ‘73

called—the soft black substance used in pencils,
curiously unlike hard porous charcoal or shining coal.
Graphite is found in granite rocks, and elsewhere
underground. It has other uses besides that of ‘lead’
for pencils, not needful to be considered here.

Charcoal and graphite are not so very startlingly
Opposite in appearance and character. But it is when
we come to the third form of carbon that we find
an astonishing difference.

The third form of pure carbon is DIAMOND.

Certainly, no one would ever dream at first sight
of putting the brilliant rare diamond under the same
head as common black charcoal and graphite.

Yet the three are the same, absolutely identical in
nature. Each is carbon; carbon in its natural free
state, uncombined, or very nearly so, with any other
substance. Unlike in colour, unlike in shape, unlike in
hardness, unlike, we should say, in every single parti-
cular—they are one in nature, formed of the same
simple substance.

So we see that—

Charcoal is Carbon ;
Plumbago is Carbon;
Diamond is Carbon.

If each of the three were formed of carbon united
with other materials, we should think nothing of it.
The extraordinary thing is, that. each of the three is
carbon only, carbon throughout.

How and under what conditions carbon takes that
peculiar form, becoming a translucent flashing gem,
we do not know. The formation of the diamond is
still a mystery. We can only assert that, as the black-
lead of a vencil is carbon, as lampblack is carbon, as



74 The Ocean of Air.

coke is carbon, as charcoal is carbon, so diamond is
carbon. Charcoal, plumbago, and diamond, however
unlike in appearance, are one in nature. They are all
three merely different developments of the one simple
substance—carbon.

Thus vast quantities of carbon are present on
earth; floating through the atmosphere in union with
oxygen as carbonic acid gas; lying underground in
rocks and coal; residing in the bodies of plants and
animals.

Moreover, as we shall see, a perpetual interchange
is kept up between the carbon of the atmosphere and
the carbon of living bodies dwelling in the Ocean of
Air. Carbon is incessantly passing from the air into
living structures, and out of those structures into the
air again. Nay, the very carbon which, ages ago,
passed into living forests of trees, is in these latter
days poured back into the atmosphere, whenever coal
is burnt.

So there is a Circulation of Carbon in the world, as
well as a Circulation of Oxygen; not less active, not
less constant, not less widely extended. The whirl-
pool of life and change knows no cessation.

By means of the spectroscope we know that this
same substance, Carbon, which is so abundant on earth,
exists also in the stars and comets of distant space.



CHAPTER xX.
THE PERILS OF CARBONIC ACID.

Cargonic Acip Gas is being perpetually made, per-
petually poured into the Atmosphere, and perpetually
broken up once more into the carbon and oxygen of
which it is formed.

The quantity of it present in the air at any one
time or place varies exceedingly.

At some times and in some places a much larger
supply is being made, and is sent floating through the
Air-Ocean than elsewhere, and on other days.

There are certain especial modes through which
this gas comes into existence.

Carbonic Acid Gas is found wherever any substance
burns which is partly made of carbon.

Part or the whole of that carbon unites itself, in the
act of burning, with some of the oxygen round about,
so forming carbonic acid gas.

One of the chief perils of a house on fire arises from
the above fact. The carbon of the great mass of
burning materials combines rapidly with oxygen, and
large quantities of carbonic acid gas are poured forth.
Many a human being, unable to escape, is mercifully
stifled by the deadly fumes, long before any flames can
reach him.



76 The Ocean of Air.

If a wind blows, so much the worse; for the moving
air brings constant fresh supplies of oxygen; and as
these sweep over the house, the making of carbonic acid
gas goes on the more rapidly. In common speech, the
wind ‘ fans the flames,’ and the house ‘ burns faster.’

When a haystack ora bonfire is alight, and we go
to the side where the wind bears down upon us, we are
speedily aware of the over-abundance of carbonic acid
gas. Whether or no we can tell its name, the fact is
apparent by the choking stifling rush which drives us
from the spot.

The same danger exists in the burning of a charcoal
brazier in a room which has no fireplace. Terrible risk
to life is involved here; for as the charcoal wastes, it
gradually unites with oxygen to make carbonic acid, and
this gas has no escape except into the air of the room.
Many a solitary being has gone to sleep in such a case,
enjoying the warmth, and has been stifled in his sleep,
never waking again.

A sad instance happened not many years ago in
Paris. A young English girl had gone there in quest of
work—a quest which long proved fruitless. Success at
last came ; and she went joyously to tell her friend, an
English clergyman, who had kindly helped in the search.
Returning to her lonely room, she lit a little charcoal
fire, feeling in delight that she might now indulge her-
self, and never dreaming of danger. Full of hope, the
poor girl went to bed, leaving no outlet for the deadly
gas; and when morning came a hasty messenger
summoned the clergyman. He arrived, only to finda
dead body lying in the small room. All had been over
hours before.

The danger is greater at night than in the day,
because one is taken unawares in unconsciousness,



The Perils of Carbonic Acid. 27

because, too, of the recumbent position of a sleeper.
Carbonic acid is a heavy gas, much heavier than oxygen
or nitrogen. Except when stirred up by air-currents,
it always sinks downward ; and it will remain so dis-
tinct from the other gases that the lower part of a
room may be full of it, while the upper part has com-
paratively pure air. Through this heaviness it can with
care be poured from one vessel to another.

Carbonic Acid Gas is made in the fermentation
of wine. The sugar contained in the grape-juice is
broken up by the fermenting process, and fresh sub-
stances are formed from it, one of those substances
being carbonic acid.

A rapid fermentation first takes place, the liquid
needing to be occasionally stirred up. For this purpose,
in olden days and in some countries it was customary
fora man to enter in bodily. The warmth of his frame
was supposed to be advantageous, by promoting quicker
fermentation. It was, however, a perilous business for
the man himself, on account of the large quantities of
carbonic acid gas escaping, and several lives were thus
lost at different times.

When the more rapid fermentation is over, the wine
is moved to other barrels, and the slow ‘ after-fermenta-
tion’ begins, lasting for months. Here,again, the same
danger attends those who have to visit the wine-vats.
As a rule, the escaping gas lies low, and a man may
walk safely upright, where his dog will fall senseless
and die; but if he stoops to care for the dog, he too
may be overpowered. Sometimes the gas collects and
rises to such a height as to imperil men also. Too
hasty an entrance into the place may mean no less than
death, and fatal results have come about not seldom.



78 The Ocean of Ain

The following memoranda are of a visit paid by my
Father to a brewery many years ago: .

‘I was taken over one of the largest breweries in
London, in company with friends. The thing that
struck me most was the large fermenting vat, of the
size and form of a small room, in which the fermenta-
tion of “wort” was proceeding at a rapid pace. The
liquor was some feet in depth, and on the surface of it
floated a dense body of clear bright carbonic acid gas,
which overflowed at the gangway where I was standing,
like a waterfall, some twelve or fifteen inchesdeep. On
looking upwards through the bright colourless gas-fall,
it was very curious to see the dingy dirty London air
resting upon its surface, and gently waving along when
set in motion by blowing or fanning.

‘I stooped down, and ventured to take a small breath
of the gas-fall, but I did not attempt to take a second.
It was like a sword passing down my throat.

‘Subsequently I inquired the cause of the pain
given by inhaling the carbonic acid gas given off by
fermentation, whereas that given off by burning char-
coal is only stifling in its effect. I was told that there
is no pain in inhaling dry carbonic acid gas, but when
mixed with damp it has the effect I experienced.’

Carbonic Acid Gas, formed by the burning of
coal, would, if we had no chimneys, be poured into
our rooms to the detriment of health, if not to the
destroying of life. Where a chimney fails to ‘draw
well,’ that is, when the upward draught is not sufficient
to carry away all the gas with the smoke, we are soon
conscious of stinging and choking sensations, ex-
tremely unpleasant in kind.

Long, long ago, English fireplaces boasted no
chimneys. The fire was made in the middle of the



The Perils of Carbonic Acid. 79

room, and the smoke and newly-formed gases had to
meander about till they found their way out through a
hole in the roof. But since glazed windows were in
those days unknown, the absence of chimneys
mattered less; for there would always be a plentiful
supply of pure air pouring in below. As cold air is
the heaviest, while hot air is light, the fresh cold in-
coming air would speedily drive upward and outward
the dangerous gas.

Most of us have felt more or less the ill effects of
burning gas in a closed room. Gas, like coal, con-
tains much carbon, and when it burns, supplies of
carbonic acid gas are being steadily poured into the
air. Unless there is a way of escape through open
door, window, or ventilator, the air of the room changes
' fast from good to bad.

Some people are very sensitive to this, suffering
even in the earlier stages from headache, faintness,
and other trying sensations, while some can endure
an extraordinary amount of bad air without being
aware of it. Sooner or later, however, the hardiest
and most insensitive frame must suffer, the condition
of things produced being one in a succession of stages
on the highroad towards suffocation.

Carbonic Acid Gas is found wherever living creatures
are. No need to say ‘ living creatures which are largely
made of carbon,’ for all living creatures are largely made
ofcarbon. From them is poured out a regular intermit-
tent stream of carbonic acid gas with every breath.

This is why a room containing human beings, if
no fresh air is allowed to enter, becomes close and un-
healthy. Burning gas would make matters worse by
hurrying on the evil. But without any burning gas;
or lamp, or candle, we have still the same result.



89 The Ocean of Air.

It is no rare spectacle to see a Church or a room
in cold weather, full of men and women, having every
door and window fast shut from dread of the slightest
draught. Elderly people and nervous people are often
afflicted with an almost morbid horror of moving air,
while they are placidly indifferent to poisonous air..
The state of things is curious but common.

Now, the air of any closed place, steadily breathed
by men or animals, becomes gradually transformed to
a slow poison ; nay, in time, to a quick poison, though
affairs are seldom allowed to go quite so far. People
are usually content to give themselves and_ their
children over-pale or over-flushed faces, sickly sensa-
tions, and bad headaches, without advancing to actual
suffocation.

We hear a great deal of ill-health among the poor,
of stunted frames, pallid cheeks, and constant suffering.
Of course, much of this in certain cases may be due to
scanty food or to overwork. But it is a grave question
how much of it is not owing to the habitual breathing
of air, which has been allowed to gain too large an
amount of carbonic acid gas, simply from the lack of
an opened window.

There is a wonderful carelessness among the poor
as to fresh air. True, the fresh air at their command
is not always of the purest; yet it is better than none.
Nor is it in town-alleys alone, but also in country
cottages, that windows are built up with plants, never
to be opened, and that frequent ‘airing’ of a room
is a thing unthought of.

It would be hardly fair, however, to speak of this
indifference as a characteristic of the poor only. There
are houses in a higher station of society, houses in-
habited by the cultivated and refined, where the window



The Perils of Carbonic Acsd. 81

rof a much-used sitting-room is closed before breakfast,
and is never opened again before night.

Naturally, by evening the air of that room has
grown into a most undesirable compound. The mix-
ture of little oxygen with much carbonic acid is
rendered not more pleasant by various floating vapours
and particles of matter, given off in the course of many
hours from the lungs and skin of each human being
present.

A sharp current of air between window and fire-
place, or window and door, would speedily expel them
all, bringing a sufficient supply of fresh oxygen. But,
no; that would be too much trouble; or nobody thinks
of it; or somebody might complain of cold. So the
unhealthy mixture has to be patiently breathed by the
unfortunate individuals assembled there. However,
as already said, many people are not sensitive.

In the space of twenty-four hours a man, not
‘especially exerting himself, takes into his system about
eighteen cubic feet of oxygen gas. He also gives off
from lungs and skin about the same amount of car-
-bonic acid gas.

Suppose a man were in a room seven feet high,
seven feet wide, and seven feet broad, shut up com-
pletely, with no opening to admit fresh air. The whole
mass of air in that little room would, in twenty-four
hours, have passed through his lungs. Of all the
oxygen originally held by the air, one quarter would
have disappeared, its place being filled by about the
‘same amount of carbonic acid gas.

Suppose no air were then admitted, but the same
state of things were continued for another twenty-four
hours. By that time half the oxygen present would
thave been exchanged for carbonic acid gas.



82 .° ° The Ocean of Air.

Following out the same idea, we may say that in
three days three-quarters of the oxygen would have
given place to carbonic acid gas; while in four days
the oxygen would be all gone, and only carbonic acid
mixed with nitrogen would remain.

Of course this experiment could never be really
tried, because long before the close the man must,
after great suffering, have died of suffocation. By
burning charcoal continuously in a shut room, from
which all fresh air is shut off, the result described
could be actually brought about; but through a man’s
breathing cnly the earlier stages are possible.

Not far from the middle of the last century, a
terrible deed was worked in Calcutta by the guards
of the so-called ‘Nabob’ Surajah Dowlah, upon his
English prisoners. No more awfully forcible illustra-
tion could be found of the desperate need for fresh
air to keep human beings alive.

The story may well be given in the vivid words of
Macaulay :

‘Then was committed that great crime, memorable
for its singular atrocity, memorable for the tremendous
retribution by which it was followed. The English
captives were left to the mercy of the guards, and the
guards determined to secure them for the night in the
prison of the garrison, a chamber known by the fearful
name of the Black Hole. Even for a single European
malefactor that dungeon would, in such a climate, have
been too close and narrow. The space was only
twenty feet square. The air-holes were small and
obstructed. “It was the summer solstice, the season
when the fierce heat of Bengal can scarcely be rendered
tolerable to natives of England by lofty halls and
by the constant waving of fans. The number of

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The Baldwin Library
University

RmB whe


THE OCEAN OF AIR




BY THE SAME AUTHOR.

Sun, Moon, and Stars. Astronomy for Beginners.
With a Preface by Professor PRITCHARD. With
Coloured Illustrations, 16th thousand. Uniform
with ‘Ocean of Air.’ Price 5s., cloth. .

The late Dr. Pusey wrote to Professor Pritchard, of Oxford :
‘Thank you also for telling me of that vivid poetic book, ‘Sun,
Moon, and Stars.” Written so religiously, it is a most fascinating
book, and would at once awaken a young mind to the glories of
the creation, and the manifold wisdom of the Creator. It takes
one’s breath away.’—Z. B. P.

The World’s Foundations. Geology. for, Be-
ginners, With Illustrations.. 5ththousand. Uniform
with ‘Ocean of Air.’ Price 5s., cloth.

‘The exposition is clear, the style simple and attractive.’—
Spectator.

Among the Stars; or, Wonderful Things in the
Sky. Astronomy for Children. With Illustrations,
4th thousand. Price 53.

*We may safely predict that if it does not find the reader with
a taste for Astronomy, it will leave him with one.’—Anowledge.

Father Aldur. The Story ofa River. For Children.
With Sixteen Tinted Illustrations. Price 5s., cloth.
‘The nature of tides, the formation of clouds, the sources of

water, and other kindred subjects, are discussed with much
freshness and charm.’ —Saturday Review.






Lightning. From a photograph by Louis S. Clarke.
By permission of the Royal Meteorological Society.
THE OCEAN OF AIR

METEOROLOGY FOR BEGINNERS

BY

AGNES GIBERNE

AUTHOR OF
‘SUN, MOON, AND STARS,’ ‘THE WORLD'S FOUNDATIONS,’ ETC

WITH A PREFACE

BY THE LATE

REV. C. PRITCHARD, D.D., F.R.S., ere.

Savilian Professor of Astronomy in the University of Oxford

* He causeth the vapours to ascend from the ends of the Earth,

He maketh lightnings for the rain :
He bringeth the wind out of His treasuries.’
Psa. cxxxv. 7.

\ : FIFTH THOUSAND

LONDON
SEELEY AND CO. LIMITED
Essex STREET, STRAND
1894
PREFACE

‘In the year 1879, the proof sheets of a little work
entitled ‘Sun, Moon, and Stars,’ now happily well
known, were placed in my hands bya friend who asked
‘me to give a passing glance over their contents. The
work appeared to me to be so excellent of its kind, and
‘gave, as I thought, so much promise of public useful-
ness, that I volunteered gratuitously the offer of a
Preface, if it were thought that I might thereby con-
tribute to its wider circulation among the intellectual
and educated classes, whether older or younger in
years. Since then I have been gratified by the fulfil-
_ment of this vaticination in the recent appearance ofa
thirteenth edition, and I think it will be for the public
advantage if it shall be even more extensively read.

A. few weeks ago, the same authoress sent me the
revised proof of the present work on the varied and
wonderful properties of the OCEAN oF AIR which
surrounds our earth, and requested my opinion on the
execution and value of the contents. I confess, at first
thought, I considered that so extensive and coniplex a
Subject required an amount of study and of accurate
information which could hardly be expected from an
vi Preface.

unprofessional author. It would, as it seemed to me,
tax the cultivated powers even of a Sir John Herschel,
and if successfully executed might take its place along-
side of his remarkable ‘ Familiar Lectures.’ After an
hour’s cursory perusal, I found myself enchained by
the multitude of pleasant thoughts suggested by the
description of the physical circumstances surrounded
by and immersed in which we pass our being; expressed,
moreover, in language at once so graphic and so simple,
that I offered, for the second time, to exert any in-
fluence which I might possess in the recommendation
of the book to the general notice of educated persons.
The points touched upon in the course of the work
are very multiform, embracing the greater part of the
natural phenomena familiar to us in our daily experi-
ence. Heat and cold, the calm and the storm, thunder
_and lightning, vapour and cloud, and rain and dew,
the passage of light and of sound, each and all of them
in their turns, receive their share of illustration in the
most pleasant of literary styles. Nor does the authoress
hesitate to encounter the marvellous conflicts of the
molecules constituting the phenomena of atmospheric
pressure and of heat and light; while, in due course,
. she extends her flight to the regions of the Aurora and
of the meteoric dust there floating and luminous, then
gradually falling on the earth and on the wide ‘surface
of the ocean, and ultimately dredged up in the form
of mineral nodules from the remotest depths of the
Pacific. A pleasant diversion is then made to the
flight of the birds of the air, and to the locusts which
are driven onwards by itswinds. It is bya fascination |
of this sort that the reader is, almost unconsciously to
himself, led toa general conception of the plan and the
Preface. vii,

!

forces of that part of the course of Nature amidst
which:he draws his breath and lives.

There are more aspects than one in'which a little
work like the present may be intrinsically valuable, and
in which that value reaches to young and old alike.
As‘to the young, it cannot fail to excite those faculties
of curiosity and imagination, which, when restricted
to their proper sphere, are among the most valuable
of our natural endowments. In most cases it will
probably satisfy the curiosity which it excites.

In respect of those who are of an older growth,
it must not be forgotten that though most of us -
are not called upon to become philosophers: or
experts, still we can, all of us, if we choose, obtain
a general and intelligent conception of the nature of
the phenomena in the midst of which we live and
move and have our being. The amount and the
‘intrinsic accuracy of our conceptions of these pheno-
mena need not be great for the ordinary purposes of
life; but to remain wilfully and purposely ignorant of
their existence and their meaning, is hardly worthy of
beings who rank themselves among the rational orders
of the creation.

It will also be found, I think, that very many of our
mental enjoyments spring from a knowledge which is far
from complete or profound, and that the most pleasant
of them are associated with a knowledge which is com-
paratively superficial. It is in the by-plays, the parerga,
of the intellect, that the better part of intellectual en-
joyment is found. It is in this direction, I think, that
we are to look for the chief recommendation of the
little book before us. Beyond this, a casual remark
here and there will probably touch chords within the
trind, which, once ‘so touched, will never cease tc
viii Preface.

vibrate and lead to trains of thought and occupation
at once harmonious and beneficent. In this way, a few
specks of dust swept up from the hearth and placed under
a modern microscope, have revealed to the instructed
eye the wonders of a tropical jungle and the formation
of: coalfields therefrom, and thereby have fired the
mind with a passionate desire for more extended know-
ledge of the primeval formations of our globe, and of
the structure of the grasses which once have clothed
them. It is trifles and accidents such as these which
not rarely have determined the whole bent and aim of
, éntellectual life.

Lastly, I think, there is another aspect under which
this unpretending little book may possess a considerable
value, and it is this: The education at our great public
schools, and even at our Universities, is yearly becom-
ing. more technical, and is falling more and more under
the domination of cram, and of the séhedule, and of
the syllabus, and of the examiner. The schoolboy is
fast becoming hot pressed. He is urged, by considera-
tions which he cannot resist, to maintain or extend the
credit of his school, either by conventional distinction
in Greek or Latin, or in what is miscalled natural
science; or, if he be hopeless in these directions, he
must, at all events, contribute to its fame by athletic |
feats. Thus his young life is marked out for him and
trammeled within narrow limits, while the actual bent
of his mind and the true reach of his natural capacity
become ignored or unsatisfied. In the palmy days of
the old school-life the boy who made but a poor figure
in his form might betake himself to collecting butter-
flies or beetles, or to keeping mice and dissecting them
when dead. In this way the foundations might be laid
for pursuits in life leading to eminence and usefulness.
Preface. ix

As things are, his natural curiosity too often is stifled,
that ‘forward-looking faculty,’ his imagination, becomes
atrophied, and his mental endowments moulded into
a stereotype. From my professional position at the
University, it is my misfortune to observe and deplore
a very large and mischievous amount of this suppres-
sion of curiosity, and a general absence of a knowledge
and love of Nature, which I take to be the necessary
consequence of the modern style of education, when
pushed, as it often is, to an extreme. I cannot doubt
but that the eminent and highly cultured scholars who
adorn the headships of our noble public schools per-
ceive and deplore this result of a system which, through
the varied pressures of social life, they are at presen-
unable to control.

It is here that I think this little volume, with its
multitudinous and interesting peeps into the nature of
the things around us, may become signally useful. If
I had now the opportunity which once I had, I would
place Miss Giberne’s little volume in the hands of the
boys in the upper forms of the school, and encourage
them to read it as an amusement and for a change of
pursuit, under the hope that the pleasant,and varied
information it contains might find a response and a
home not reachable by the ordinary routine of school-
life. What I have here indicated as serviceable
for boys, is at least equally so for the other sex; nor,
as I have already said, do I think its interest or utility
is limited to the years of our youth, seeing that it was
not without a species of fascination that I read it
myself. It is, indeed, but a Httle book, but it treats
of many objects and many phenomena of constant
occurrence, and it possesses the great advantage that it
can be taken up and laid down again piecemeal, and at
x Preface.

fragments: of time. . Bread ‘thus’ cast: upon :the waters
willbe: found hereafter in an abundant harvest. of
~pleasant associations for hours of contemplation or of
leisure: éev.

C. PRITCHARD.

UNIVERSITY OBSERVATORY,
October, 1889.
AUTHOR’S PREFACE

AFTER the generous words of Dr. Pritchard about my
little book, there is small need for me to say much.
First and foremost, I must express my hearty gratitude,
not only for the warm praise which he has accorded,
but also for the infinite trouble which he has taken in
reading the Revise, pointing out some weaknesses and
here and there suggesting improvements. I can never
forget what I owe to his kindness, both with this book
and with ‘Sun, Moon, and Stars.’

In writing ‘The Ocean of Air,’ I have had a wish
to make it one in a trio of volumes. It may be said to
occupy a position between my two earlier scientific
books. ‘Sun, Moon, anp Stars’ had for its subject
the vast realms cf space, dotted with suus and worlds.
‘THE Wortp’s Founpations’ had for its subject the
Crust of our Earth, and the Story of that Crust’s for-
mation. ‘THE OCEAN oF AIR’ has for its subject
the expanse dividing the two—that broad belt of Atmo-
sphere, which rests upon Earth’s Crust and reaches
upward to surrounding Space.

I might end with a catalogue of hooks.and Cyclo-
xii Author's Preface.

pzdias to which I have had recourse for information ;
but many of them are referred to in the following pages,
and the entire list would be cumbrously long. So I will
only close with a word of particular acknowledgment
to the authors of any extracts which I have ventured
to make without writing to ask express leave. I trust
that, in such cases, the omission will be pardoned.

WorTON HOUSE,
EASTBOURNE.

October, 1889.
CONTENTS

PART I.
USES OF THE AIR-OCEAN.

CHAPTER VAGâ„¢
I. THE AIR IN WHICH WE LIVE - - - - 3
Il, WHAT THE WORLD WOULD BE WITHOUT AIR - 15
III], THE WEIGHT AND STATE OF AIR - - - 23
IV. AIR AS A MIXTURE - - - - - 33
V. AIR AS A PART OF EARTH - - - - 38
VI. THE RESISTANCE OF AIR - - - - 44

PART II.

GASES OF THE AIR-OCEAN.

VII. TIIE USES OF OXYGEN - - - - 85
VIII. WHAT IS MEANT BY BURNING - - - 62
IX. THREE FORMS OF CARBON” - - - - 70
X. THE PERILS OF CARBONIC ACID - - - 75
XI. WHAT IS MEANT BY BREATIIING— - - - 89
XII. HOW PLANTS WORK - - . - - 102
PART If,
VAPOURS OF THE AIR-OCEAN.
XIII, WATER IN THE ATMOSPHERE | - - - 113
XIV. ABOUT EVAPORATION - - - - - 121
XV. ABOUT CONDENSATION - - - - 129
XVI. DEW, MIST, AND FOG - - - - - 135
XVII. THE MOUNTAINS OF CLOUDLAND~ - a - 143

XVIII, RAIN, SNOW, AND HAIL - - - - 153
xiv Contents.

PART IV.
MOVEMENTS OF THE AIR-OCEAN.

CHAITER . PAGE
XIX. THE NATURE OF WIND -. - - - 165
XX. THE CIRCULATION OF AIR: - - - - 17>
XXI. MORE ABOUT THE WILD WINDS” - - - 181

XXU. THE GREAT WATER-CIRCULATION - - - 190

PART V.
DISTURBANCES OF THE AIR-OCEAN. |

XXIII. CLIMATE - - - - - - 203

XXIV. WEATHER - .- - - - - 212
XXV. EDDIES OF AIR - - - - - 221

XXVI. WHIRLWINDS AND TORNADOES - - - 230

XXVII. THUNDER AND LIGHTNING - - - + 239

PART VI.
FORCES OF THE AIR-OCEAN.
XXVIII. ELECTRICITY AND MAGNETISM - - - 245

XXIX. HEAT - - - - - - - 259

XXX. SOUND AND LIGHT - - - - - 270

XXXI. ATOMS AND MOLECULES - - - - 283

XXXII. A BUSY WHIRL - - - - - 290
PART VIZ.
LIFE IN THE AIR-OCEAN,
XXXII, DUST OF THE AIR. - - - - - 299
XXXIV. LIVING DUST OF THE AIR - - - - 311
XXXV. INSECTS OF THE AIR - - - - 316°

XXXVI. BIRDS OF THE AIR -_ -. - - - 325
LIST OF ILLUSTRATIONS

Engraved, by permission, from Instantaneous Photographs,

PAGE
LIGHTNING - - - - - - Frontispiece

THE YACHT ‘MOHAWK’ IN A BREEZE - - - I

ao

CLOUDS OVER LOCH EIL, FROM THE SUMMIT OF BEN NEVIS 12

iS}

MIST - - > - - - - - 136
HOAR-FROST - - - - - - 140
CLOUDS ON THE HIMALAYAS = - - - - 146
CUMULUS CLOUDS - - - - - - 150
SNOW ON THE WESTMORELAND MOUNTAINS - - 156
ICICLES FROM A WATERFALL - - - 160
WIND-BLOWN TREES - - - - - - 168
BREAKERS AT BOGNOR - - - - ~ 84
WAVE BREAKING OVER TIIE SEA-WALL AT BOGNOR - 186
SNOW ON THE SLOPES OF THE HIMALAYAS - - - 204
A WAVE AT HASTINGS - - » - - - 226
A FROZEN TORRENT + . . - - - 262

FLIGHT OF SEA-BIRDS - - - - - - 326
PART I.
USES OF THE AIR-OCEAN,
CHAPTER I.
THE AIR IN WHICH WE LIVE.

Our Earth has many robes.

Closely-fitting garments come first, of brown soil
or gray rock and green grass, with wide liquid under-
skirts of deep blue filling up the spaces between.

Outside these are coverings more wonderful still;
fragile yet strong, transparent, almost invisible, folded
around layer upon layer, or, as one might say, veil
upon veil, each more gossamer-like than the last.

These form Earth’s surrounding Atmosphere—a
substance pervading everything, found everywhere.
One may travel from the equator to the poles, one may
journey by sea or by land, one may soar high in a
balloon or descend deep into a mine, but one can
never in this world go to a place where the Atmosphere
is not. —

A substance—for air can be felt; air has weight; air
occupies space; air, like any other body, can be made
hot or cold; air is composed of particles of substantial
matter.

A child, not to speak of a grown-up person, opening
a box which holds only air, will naturally say, ‘ Nothing
here!’ But something is there; something very definite
and real, and of no small possibilities. Those same
quiet air-particles, actually unfelt by the hand moving

I—2
4 _ The Ocean of Air.

gently among them, have strength, when stirred into a
hurricane-blast, to uproot huge trees, to sweep away
vast buildings, to raise ocean-waves upon which mighty
ships are tossed helplessly about ‘ like eggs in a boiling
cauldron.’

Air may be felt. The faintest breeze cannot stir
without a man becoming conscious of the air-particles
striking against his face. He cannot ride or run
through the air without the same sensation. If he
even moves his. hand quickly enough to and fro he is
aware of something resisting his hand.

Air can be made hot or cold. We all know from
experience the difference in our feelings when cold air-
particles on a frosty winter’s day, or hot air-particles
on a sultry summer’s day, strike against our bodies,
either giving over to us of their heat, or stealing away
some heat from us.

Air also has weight, and occupies a certain amount
of room. Just as a mass of iron or of lead weighs so
much, a mass of air has its own particular weight.

This means that air, like iron or lead, is subject to
earth’s attraction ; which is only tantamount to saying
again that air is a substance. Nothing which is not
a substance can possibly be attracted by a substance.

If air is a substance it must occupy space, it must
take up room. It may be very light, very slight, very
elastic, and very compressible. Other bodies may pass
easily among the air-particles, pushing them apart, or
squeezing them closer tog-ther. Yet space it must
have. Air, being distinctly a something, has to be
somewhere.

Air has a faint bluish tint, which on a sunshiny day
becomes in the sky a very pure and deep blue. This
The Air in which we Live. 5

tint is not believed to be the natural colour of the
atmosphere. Were it so, the air would merely act the
part of a blue pane of glass, rendering the white light
of the sun blue as it reaches our eyes; but the blue of
the atmosphere is known to be a reflected blue.

If reflected, there must be something in the atmos-
phere to reflect it; and such indeed is the case. Per-
fectly pure air would doubtless be without colour, but
perfectly pure air we do not find. The whole atmo-
sphere is full of multitudinous minute specks, so small as
to be in themselves invisible, so light as to remain aloft.
To the presence of these the blue tint is believed to be
due. They scatter the light of the sun, and prosace
the blue effect.

A beam of strong white light, caused to pass through
a liquid which contains a large supply of minute floating
particles, is affected by them in a like manner. The
short blue waves are more abundantly reflected than
the long red waves ; and so the water seems to be blue.
This explanation serves for the deep-blue colour of the
ocean, as well as for the blue of the atmosphere.

The whole Earth is surrounded by this marvellous
Air-Ocean; an ocean of gaseous matter, at least one
hundred times as deep as the water-ocean.

At the bottom of the gaseous ocean we small
human creatures crawl about, commonly on flat lower
levels—the ocean bottom, in fact. Sometimes, with
much toil and trouble, we climb the little ridges and
mounds called ‘ mountains ;’ little compared with the
depth of the atmosphere, though not little compared
with ourselves. The highest mountain-peaks of even
the vast Himalayas lie low down near the bottom
of the Ocean ot Air.
6 The Ocean of Air.

Our position is, on a bigger scale, much the same
as that of the crabs and cray-fishes crawling laboriously
about;at the bottom of the sea-water tanks in the
Brighton Aquarium. Only, they are in a minute world
of water, and we are in a large world of air. They
have over their heads only a few feet of the fluid*
in which they live. We have over our heads many
miles of the fluid* in which we live.

Also, it seems probable that they cannot see beyond
their confined regions of water, while we have eyesight
which can pierce far beyond our wide regions of air.

But the very extent of the Ocean of Air adds to our
difficulty in studying its nature. All observations that
we can make must be limited by the state of the
atmosphere just around ourselves. We can never get
out of and beyond the atmosphere, so as to see it asa
whole. At any time a slight local fog is enough to put
a stop altogether to such observations, beyond the
unpleasant experience of the fog itself.

Just so a crab, wishing to study the general condi-
tion of the water in his tank from one corner of it,
would be hampered by the stirring up of a little mud
or sand in his own neighbourhood.

In all study of Earth’s airy envelope we have to
allow for these difficulties ; to confess ourselves apt to
blunder; and not to dogmatize hastily upon questions
about which we are not well informed.

We can never in this life get beyond the Ocean of
Air; for man and beast cannot live without air. To
breathe means life; to cease breathing means death.
That which we breathe is the air around us—the ocean
of almost invisible gases.

* Air and water are both ‘fluids,’ though different in kind,
The Air in which we Live. ”

It used to be supposed that the atmosphere reached
only to a height of about fifty miles above Earth’s
surface.

We are driven here to conjecture, to some reason-
ing from certain tokens, and perhaps to a good deal of
guessing. Being always imprisoned at the bottom of
our ocean, we cannot measure for ourselves how far it
extends above.

Of late years the opinion has gained ground that
the atmosphere reaches to a height certainly of two or
three hundred miles, probably of four or five hundred,
possibly a good deal more. But the condition of the
air far above is different from that of the air in lower
levels, where we live and breathe.

The higher we ascend, the more thin or ‘rare’
becomes the air. A less quantity fills a certain space
up there than down here. The particles float farther
apart one from another.

This difference in the density of the air is chiefly
due to Attraction.

Each separate air-particle is drawn steadily earth-
ward by the Force of Gravitation, and that force is
stronger on the surface of earth than at a distance.
The closer to earth, the heavier the pull; the farther
from earth, the less the pull.

Besides the actual attraction of the earth drawing
the air-particles downward, there is the great weight
of the whole atmosphere above, caused by the same
attraction. Miles and miles of air overhead press
mightily downward, packing tightly together the lower

layers of air near to earth’s surface.

If thousands of bales of cotton-wool were piled
into an enormous heap, the upper layers might be
light and loose in their make, but the lower ones would
8 The Ocean of Air.

be squeezed into a very small compass by the pressure
of the mass above.

Without this pressure of the overlying atmosphere,
the air down here would not be nearly so dense as it
is; and, indeed, would not be fitted to support life. A
man ascending a mountain or rising in a balloon leaves
heavy layers of air below, and has an ever-lightening
weight above, so that the atmosphere around him be-
comes constantly more thin, more difficult to breathe.

This difficulty is felt to a severe extent by those who
climb the greater mountains. Within certain limits of
height the air is only more light and exhilarating, be-
cause a little less dense, than on the plain. But as its
rarity increases, the breath gets short, the heart’s
action is quickened, the sense of oppression grows
painful. If the ascent could be continued indefinitely,
death from suffocation would result. »

The loftiest mountain-top upon earth stands only
about five and a half miles above the sea-level. No
man has ever yet climbed to such a height, and pro-
bably no man ever will. It might not be impossible
to exist for a while upon the summit, but one can
hardly imagine any man able to reach any such level
by climbing. The thinness of the air must long
before have so reduced his powers as to render active
exertion out of the question. If some means could
be devised for bearing him to the summit of Mount
Everest, loftiest of the Himalayan range, he would
probably, when there, be fit for little more than to lie
panting on the ground.

Mount Everest* has never yet been scaled by men,
though ardent mountaineers long ago reached to a

* Mount Everest is over 29,090 feet high; Chimborazo, over
19 500 feet ; Mont Blanc, over 15,700 feet.
The Air'in which we Live. 9

level of over 19,000 feet in the Himalayas. This, too,
has been done with the monsters of the Andes chain,
once supposed to be the highest. mountains in the
world, though now known to be far surpassed by the
giants of North India.

In the beginning of the present century Humboldt
made a vigorous attempt to scale Chimborazo, one of
the loftiest of the Andes. He and his party suffered
severely from sickness, giddiness, and difficulty in
breathing, and the attempt proved a failure. Not till
over seventy years later was the ascent actually
accomplished by Mr. Whymper.

This time, too, the daring climbers were almost
incapacitated by weakness, headache, fever, and breath-
lessness, yet with desperate resolution they held on
till the summit was gained. After camping for a night
at a level above the utmost height of Mont Blanc,
they stood at length victorious, nearly 20,000 feet above
the sea. ‘Theascent of the last thousand feet,’ we are
told, ‘occupied five hours;’ for a large tract of ex-
traordinarily soft snow had to be crossed, and ‘it was
found necessary to flog every yard of it down, and
then to crawl over it on all fours.’ Such exertions, at
so great a height, and in so rare an atmosphere,
speak well for the indomitable spirit of the travellers.

De Saussure, ascending Mont Blanc in August,
1787, suffered from extreme distress and exhaustion.
On the highest ridge he had to halt every fifteen or
sixtcen steps, sometimes even to lie down; and the
robust guides with him were in absolute danger of
fainting. The same excessive weakness was felt by
certain other well-known climbers in 1844. But this
experience is by no means universal. The effect of the
rarefied air differs extremely with different individuals.
10 The Ocean of Air.

Moreover, use greatly modifies and even to some extent
does away with these effects. In the Andes there are
cities full of people, at a height of 12,000 or 13,000 feet,
and no inconvenience results from the thinner air,

Carried upward passively in a balloon, without effort,
men have risen higher than the highest mountains.
Mr. Coxwell and Mr. Glaisher in their celebrated aerial

re An Oa, Onflens

> voyage of 1862 are believed to have mounted seven

3 miles above the sea. No little peril and suffering

© were involved, alike from the extreme thinness of the
Se air, and from the bitter cold.

The wish to fly like a bird is an old wish among
men. Perhaps it is a form of the restlessness which
dislikes to be tied down anywhere; perhaps it partakes
of the ‘excelsior’ feeling which would fain reach
regions inaccessible. Tied down we undoubtedly are
to the lower depths of the Air-Ocean, and inaccessible
the higher regions undoubtedly are to us.

Various mad attempts at flying have been made
from time to time, more or less disastrous to the
makers of them. When, however, near the close of
the eighteenth century, a balloon was first made and
sent up, men thought they had at last won the mastery
of the atmosphere. They did not at once find out that
floating is not flying; that the balloon at its best is still
only ‘an unmanageable despot’—a despot over the
men whom it carries, and itself a complete prey to the
despotic winds and breezes.

No means of steering or guiding a balloon has yet
bcen discovered.* Where the air flows the balloon goes,

Aen? fA thahe th,

dl

/ ar

i

; CK/
C An 1909

* Attempts are now being made to construct an ‘air-ship,’ able
~ to plough its way through opposing winds ; whether successfully
or no, time will show.

a
The Air in which we Live. II

fast or slowly, according to the degree of wind. No
balloon ever cuts its way through the wind, or travels
contrary to a breeze; it is simply swept to and fro by
the atmosphere, as a cork is borne to and fro by the
ocean.

The first public balloon ascent took place in June,
1783. A fire-balloon, made of linen and said to be filled
with smoke, went up from near Lyons, and a furore of
excitement followed. Silk balloons, filled with hydrogen
gas, were made next,‘and the earliest ascent of man
followed. A successful though perilous attempt to
cross the Channel took place about two years later.

Many aerial journeys were made, some ending well,
some fatal to the unfortunate voyagers. As the dangers
of these attempts became better known, and as their
comparative uselessness for almost all except scientific
purposes grew more apparent, public interest in the
matter faded. During the early half of the present
century balloons were little thought of; but more lately
there has been a revival of interest.

Some very remarkable ascents have been made by
the famed aeronauts, Mr. Coxwell and Mr. Glaisher.
One or two of these are especially worth mentioning.

In their second ascent from Wolverhampton, the
balloon sprang rapidly upwards, and in about ten
minutes was hidden by a cloud. It reappeared ;
vanished again; was seen at a height of perhaps
three miles; disappeared anew; then gleamed in the
far distance as a transparent ball, shining moon-like in
the sunbeams. The journey lasted from about one.
o’clock till half-past four; and in that interval the
balloon ascended four miles and a half.

The voyagers suffered from severe ‘sea-sickness,’
though not from bleeding of the nose or singing in the
12 | The Ocean of Att

ears, popularly expected on such occasions. They had
enough to bear without these additions. Mr. Glaisher
held manfully to his task, observing and noting down
the state of the atmosphere minute by minute, despite
sickness, brain-pressure, violent headache, and a pulse
at 108 per minute, all due to the rarity of the air.

The view seen from above must indeed have been
marvellous. No veil of intervening clouds shut off
what lay below, and the earth was visible, not asa
rounded surface, but as a seeming hollow, with a
distant horizon rising high all around, like the.rim of a
saucer or an inverted watch-glass. The intense black-
blue of the sky, as seen from great altitudes, is well
known to mountain-climbers. Here, however, the blue
seemed to be everywhere; a mighty expanse of pure
blue filled the vast hollow, reaching to unlimited depths
above; ‘an immense shoreless ocean ’—the Ocean of
Air in which these daring voyagers floated. A ‘ bound-
less sea’ of ever-changing clouds, piled in mountain
masses, and dazzling the eyes with their snowy glare,
followed more or less the lines of the horizon, often
closing in below to shut off the solid ground.

As the balloon rose higher, the pervading blue grew
brighter, and earthly sounds waxed faint.. One mile
high, human voices might still be heard, raised in a
shout ; two miles high, only a dog’s sharp bark could
be distinguished.

Since a balloon moves with the moving air, there
are no jars or jolts, no struggles to advance, as with
a ship at sea—-nothing resists its passage. The
movements of a balloon seem, indeed, to be charac-
terized by a singular quietness, so far as regards the
voyagers’ sensations. When it first rises, the earth
appears to drop away: when it descends, the earth
The Air in which we Live. Iz

appears to rise. There is little consciousness: of
motion. i

This delusion was quaintly expressed by a certain’
American aeronaut. He was, he says, ‘ preparing to
come down gently, when the earth bounced up against
the bottom of his car.’ A more terse description
could scarcely be offered.

The most remarkable ascent known was that of
Mr. Glaisher and Mr. Coxwell on the 5th of September,
1862, when they rose seven miles. If we remember
that Mount Everest, of the Himalayas, is nearly twice
the height of Mont Blanc, and that the voyagers were
floating a mile and a half higher than the height of
Mount Everest’s topmost peak, we shall better imagine
the perils of this excursion. No human beings have
ever ascended further. The marvel was that they re-:
turned to earth alive.

In those lofty regions of the Air-Ocean no living
creatures exist. The voyagers passed through bound-
less silent solitudes—silent except for the hurried beat-
ing of their own hearts, the sound of their own panting
breath, the sharp ticking of their watches, and the
‘clang of the valve door.’

On leaving earth the thermometer stood at 59°.
Soon afterward the balloon passed through masses of
cloud, thousands of feet in depth, then came out into
dazzling sunshine, with a deep-blue sky above and
countless mountain masses of billowy cloud below.

As they rose, they released at intervals a captive
pigeon. One set free at a height of nearly five miles
‘fell downward like a stone.’ Of two others taken
higher, one died of the cold and the other was stupefied.
When they reached five miles above the sea, the tem-
perature was below zero.
14 The Ocean of Air.

Still upward, further upward, rose the resolute pair.
Then blinding darkness and insensibility seized Mr.
Glaisher. Had he been alone, he could never have
revived. With no one to open the valve, the balloon
must have carried him onward into yet higher and
deathlier regions, where for lack of air he would have
perished. ;

Even then Mr. Coxwell did not at once give in; but
he was strictly on the watch. At the seven miles’ level,
a tremendous height, he too felt signs of failing con-
sciousness. In a few minutes more all would have
been over with them both, and at last he yielded. It
was indeed time that he should. His hands were
powerless to act, but he seized the valve-rope in his
teeth and pulled. The gas rushed out; the balloon
steadily sank. Both lives were saved, and a mighty feat
had been accomplished.

Yes, a mighty feat, and a tremendous height—in
consideration of human powers! Seven miles high
would seem to be the outside limit at which animals
generally can exist for even a short time. Birds may
be to some extent an exception. Certain birds are
believed to soar occasionally two or three miles higher
still.

But what are seven miles—what are even ten miles—
compared with the four or five hundred miles of atmo-
sphere-depth ? With all our utmost efforts, we and the
birds still find ourselves only able to creep and flutter
on or near the floor of the Ocean of Air.
CHAPTER II.
WHAT THE WORLD WOULD BE WITHOUT AIR.

Wuat Earth would be without her surrounding Ocean
of Air, we can scarcely imagine.

The Atmosphere plays so extraordinary and essential
a part in all around, that to picture its entire absence is
not easy.

We see faintly on the moon something of what an
airless world must be. Yet since we only ‘see’ froma
distance of two hundred and forty thousand miles, that
does not mean much. Imagination has to come in,
and imagination is apt to play us curious tricks when
running after affairs which lie outside the range of
human experience. —

No man has ever yet been to an airless world. If
he could get there, he could not live there ten minutes.
He would be worse off than the aeronauts seven miles
above earth’s surface. They had at least some air,
though but a scanty amount; while he would have
absolutely none.

Without air, man and beast cannot breathe. With-
out air, plants and trees cannot grow. Without air, life
as we know it—the lower animal life common to man
and beast—is a thing impossible. Without air, our
world would be, as we suppose the moon to be, a world
of lifelessness.

Air is earth’s outer robe, ‘for use and for beauty ’—~
16 The Ocean of Air.

for use in modes uncountable; for beauty, not so much
in itself, as in the softening, the diffusing, the con-
trolling effects of its presence.

Air is a mighty Ocean, in which all things living
must dwell. Even the living things of the sea are not
exceptions to this rule, for water itself is pervaded by
air. A man, going into and under water, does not get
beyond the touch of air; only, not being provided, like
fishes, with breathing gills, he cannot make use of
what is there—he cannot separate the air from the
water, and so keep himself alive by breathing it.

Some animals living in the water-ocean are as
dependent upon the Air-Ocean as man himself for ‘ the
breath of life.’

Whales are a remarkable example of this. They are
not fishes, though often mistakenly called so, but belong
to the same ‘family’ of creatures as men and land-
quadrupeds generally. A whale is warm-blooded, has
no gills, and breathes atmospheric air, coming to the
surface for it.

A whale, kept forcibly for a long while under water,
would be drowned exactly as a man would be... If
a whale is thrown upon the shore, it does not die of
suffocation, but of inanition. A fish’s gills are no more
fitted to breathe air in bulk, than a man’s lungs are
fitted to breathe air diffused in minute particles through
water. The fish out of water is suffocated by getting
air too rapidly: the man under water by exactly the
reverse. A whale breathes like a man, and on land it
simply starves fast from lack of the incessant food re-
quired by such a huge carcase.

There is a difference certainly between man and
whale in the matter of breathing. A man has to take
in fresh supplies of air constantly, and if he is beyond
What the World would be. without Air. 17

xeach of air for more than’a few minutes he dies. A
whale comes to the surface for about: ten. minutes,
spouting out enormous supplies of used-up air and
taking in enormous supplies of fresh air, after which it
can remain under water for half an hour or more :. some
say an, hour. Then a fresh bout of noisy breathing
becomes an absolute necessity.

This, however, is merely a matter of internal
arrangement. The whale has an immense reservoir
of blood, which, being thoroughly. purified by the air
during ten minutes of vigorous breathing, serves slowly
to supply the creature’s requirements while below. But
the need for air, and the effect of that air upon the
blood, are much the same in man and whale. ~

Small creatures, as well as large ones,. spending
much time under water, and yet breathing air, have to
come regularly to the surface.

The great water-beetle, for instance, while able to
live on land, is a very incapable being there, and seems
at home only in the water. Like other insects, it has
no lungs, and breathes air into its body through tiny
holes in its sides. Lungs or no lungs, air it must
have, or like man and whale it must die. So, after the
fashion of the whale, it rises to the surface to breathe,
:and not having the happy internal arrangement of the
whale, one would expect it to be compelled to dart up
incessantly for fresh air. But here we find another
Provision, equally wonderful. ;

The hard polished wings of the beetle, neatly fitting
and fast shut, inclose between themselves and the body
a water-tight hollow, into which the breathing holes
open... This hollow is filled with air when the creature
comes to the surface of the pond, and while the little
supply is being gradually breathed, the beetle may

2
18 The Ocean of Air.

safely remain below. Not till it is used up does a
journey to the surface for a fresh supply become neces-
sary.

Another such instance is seen in the water-spider,
a creature, again, which can exist on land, but is
more at ease in water. When the spider dives, it
carries downward countless tiny air-bubbles, caught
and imprisoned among the fine hairs which cover its:
body.

This is not all. The spider has also an extra-
ordinary power of conveying down at will, between
body and folded legs, a large bubble of air for a par-
ticular purpose—to supply the little home below. The
said ‘home’ is a cocoon, spun by the female spider in
readiness for eggs. Having prepared a cocoon, the.
spider dives with a big air-bubble, and lets it loose
within the cocoon, where it remains, driving out an
equal quantity of water. Bubble after bubble being
carried to the spot, all the water in the cocoon is.
gradually replaced by air, and the tiny dwelling becomes.
habitable.

So much as to the need of air for living creatures.
If our world had no Ocean of Air, there could be on
earth no men, no quadrupeds, no whales or fishes, no.
birds or insects, no forms of life.

Like the ocean of water, the Ocean of Air knows no.
repose or stagnation. What we call stillness on the
most sultry of summer days does not mean absolute.
stillness. Though not enough wind may stir to lift a
feather, yet the air is in ceaseless motion, to and fro,
hither and thither. The whole atmosphere is a vast
and complicated system of air-currents, and each lesser
portion of air has its own lesser circulation. You


The Vacht“ Mohawk” in a Breeze. From a photograph by G. West & Son.
What the World would be without Air. 19

cannot lift your hand without causing a tiny breeze;
you cannot turn a wheel without making a minute
whirlwind; and every separate air-movement draws
other movements in its train.

There is water enough on earth for all needed
purposes; but we should find ourselves in direful
straits if the whole water-carrying from lakes and
rivers for men and animals had to be performed by
human agencies.

Far from this, a mighty apparatus is provided.
The scanty aid that man can give only shows how
little he is capable of.

The entire atmosphere is a tremendous pumping-
engine, an enormous watering-machine, always at work;
always recciving supplies of liquid from the ocean, from
seas, lakes, rivers; always showering this water down
again upon the land, as needful drink for plants and
animals, as needful cleansing for all things.

Air, the great carrier of water, in its wonderful
strength and restlessness, bears vast layers of cloud to
and fro, wafts away superfluous damp, drenches the
dry and thirsty earth, fills ponds and lakes, feeds—nay,
actually makes—the rivers, never flags in its ceaseless
energy.

If clouds hang low or fogs arise, we are glad of the
moving air which sweeps them elsewhere. If the soil
is caked and plants droop, we are glad of the moving
air which brings rain.

Thus our wants are supplied, and the wide Water
Circulation of earth is carried on. Without circu-
lation, without motion, stir, change, there cannot
be life. Stagnation must mean death. Our Earth,
without her Ocean of moving Air, would be a world of
death.

2—2
20 - The Ocean of Air

Without air, Earth would be in great measure a
soundless world. Silence would reign here, as pro-
bably it does reign on the moon.

Sound, as it commonly reaches our ears, depends
for its very existence upon air. Let the concussion of
two bodies be ever so mighty, if there were no air to
bear away the vibrations of that concussion, there could
be no crash of sound.. True, sound-waves can be
conveyed through a liquid or through a solid as well
as through air; and we might be conscious of the
ground’s vibrations, but our ears would hear no noise.

So an airless world would be a silent world. With-
out air, supposing we could ourselves exist, we should
hear no trickling brooks, no rush of waterfalls, no
breaking ocean waves, no sighing of the wind, no
-whisper of leaves, no singing of birds, no voices of
men, no music, no thunder, no one of the thousand
concomitant sound-waves which together make up the
babble and murmur of country and town. Those only
who are perfectly deaf can know what such silence
means.

Without air our world would not be in darxness;
for light does not, like sound, depend mainly upon air
for its transmission. Light travels through regions
where air is not; and if light is communicated by
waves, they are not waves of air. But though the
absence of air would not deprive the earth of light,
‘it would make a very great difference in the kind and
degree of light received.

Without air the blue sky would be black as ink;
stars would glitter coldly in the daytime beside a
glaring sun; deep shadows would alternate with blind-
ing dazzle, and all the soft tints of sunrise and sunset
Whee the Wold would beret Aine. 88

would be wanting. Earth would be like the almost
airless moon—all fierce whiteness and utter blackness
—with no gray shades, no rosy gleams, no golden
evening clouds; nay, without air there could be no
clouds. =

On the moon is no twilight; for no air-particles
float about, reflecting the sunlight from one to another,
and forming a soft veil of brightness, to reach farther
than the direct sunlight alone can reach.

Sunbeams travel straight to earth, unbending. as
arrows in their flight, and unaided they cannot creep
any distance round a solid body, though they may be
reflected or turned back from it. But the air breaks up
the sunbeams, bends them, diffuses them, spreads them
about, surrounds us with a delicate lacework of woven
light.

A sunbeam travelling through space is invisible till
it strikes upon some object. If that object is solid,
the light of the sunbeam is partly absorbed, partly
reflected ; if the object is transparent, the sunbeam
passes through and onward. Few substances, if any,
are perfectly transparent. We call air transparent, yet
it is so only ina measure. Each sunbeam passing
through the atmosphere loses part of its brightness by
the way, and so the great glare of the sun is softened
before it reaches the lower depths of the Air-Ocean.

The sun’s rays are rays of heat as well as of light.
While the atmosphere softens the glare, giving us
shade and twilight, it also modifies the extremes of
temperature, from which, without air, we should suffer.

When the sun goes down, although we are often
conscious of a chill, it is not the instant and over-
whelming chill which we should feel but for the atmo-
sphere. All day long the sun has been warming the
22 The Ocean of Air.

earth and air. When his direct rays are withdrawn,
the warm air for a while keeps its warmth, and gives
over of that warmth to us.

We talk often of ‘warm winds’ and ‘cold winds’
from different quarters. By ‘warm winds’ we mean
air that has passed over a warm surface of land or sea,
so gathering up and bringing heat to us. By ‘cold
winds’ we mean air that has passed over a cold surface
of land or sea, so parting with some of the heat it had
in a measure, and reaching us in a chilled condition.

People living in England are very much warmer
than their friends across the Atlantic living no further
north. Here the weather is mild when there it is
bitterly cold. There they are ‘frozen up,’ when here
we have only a little fitful frost and snow.

The main reason for this difference is that abund-
ance of soft warm air comes drifting over us from a
certain ocean-current, called the Gulf Stream, flowing
northward in our direction from the tropics. Our
friends across the ocean receive a like abundance of
cold air from a cold ocean-current, flowing southward
from the frigid zone.

All this would be altered had we no enfolding Ocean
of Air.
CHAPTER III.
THE WEIGHT AND STATE OF AIR.

IF one would understand the Atmosphere as a whole,
one must learn something about the laws which govern
its movements.

That air is a substance, and therefore is heavy like
any other substance, has already been explained.

We are apt to talk of things as heavy and not
heavy, as if some things had weight and some had
not. But every substance without exception has
weight.

A certain gas, called hydrogen, does not commonly
fall downward, but rises through the air upward. If
we wish to send a balloon towards the sky, we only
have to fill it with hydrogen gas, and it is sure to
ascend.

Yet, hydrogen gas is a substance, and has weight.
Only its weight is so very much less than the weight
of common air, that the air-particles fall naturally
below, and press the lighter particles of hydrogen up-
ward. This is how a balloon rises; not because it
has no weight, but because it weighs less than air.
A cork has weight, yet in water it springs to the top,
because it weighs less than the same bulk of water.

A feather, light as we count it, has weight, and if
dropped in a closed vessel, emptied of air, it will reach
24 The Ocean of Air.

the bottom quite as fast asa lump of iron. From its:
light and spreading make, it is easily buoyed up and
carried along by the slightest breeze; but if the air is
still it soon finds its way downward.

Until nearly the middle of the seventeenth century,
nobody so much as suspected the fact that air had
weight. When Galileo was an old man of seventy-
six, he was the first to gain a glimpse of the long-
hidden truth; and his pupil, Torricelli, followed out
his experiments, proving him to be in the right:

Weight is caused by a wonderful force or power,
which holds sway, not only on earth, but in the sun
and the planets, and throughout the universe—the
Force of Gravitation.

Every substance attracts every other substance to-
wards itself with a greater or less degree of strength, de-
pendent on the size, the make, and the distance of each.

If no substance attracted any other substance,
there would be no such thing as ‘weight.’ When we
speak of a mass of iron being ‘heavy,’ we mean that
the earth draws it downward. When we speak of the
whole Atmosphere having weight, we mean that it,
too, is pulled earthward.

The attractive force which causes all objects to
draw nearer together, when not prevented, we know
by its effects, and by its effects only. We see what
it does, not what it is. That such a force exists we
perceive; that such a law or order prevails we know.
But what the force is in itself, and in what mode one
substance influences another, none can tell us. Search
as we may, and rightly may, into these things, solving
one perplexity after another, we find ourselves sur-
rounded still by baffling walls of mystery.

We call Attraction one of Nature’s Laws, or one of
The Weight and State of Air. 25

Nature’s Forces. Either term leaves us where we stood
before. The forces of Nature are the forces of the God
of Nature. The laws of Nature are the laws of the
God of Nature; they constitute the ‘Plan’ on which
the Universe and all that is therein are framed. And
because they are His laws, His forces, and because
He is our Father, we, His children, may well search
into them with the utmost of such powers as He has
givenus.

The Air of our almost invisible Ocean is often de-
scribed as an elastic fluid, but this gives no clear idea.
of its condition. A fluid may be either a liquid or a
gas; and liquids are by no means the same as gases.

There are three distinct forms known to us of
the same substances upon Earth. These three states
or forms are—the Solid; the Liquid; the Gaseous. A
simple illustration is to be found in water.

Suppose a man should travel to earth from some
far-off region of space, having never seen our common
earthly substances, having never come across water in
any of its various conditions. He must not, by-the-bye,
‘hail from’ the planet Mars, since there, at least, we
haye good reason to believe, snow not only exists but
thaws, which means the presence of water as well
as of ice.

Suppose, on arrival, he should alight first upon a
Greenland glacier, having hard ice all around him.
He would naturally describe water as ‘a species of
rock.’ For thus far he would know it only in the solid
or frozen form.

If he landed first on the border of the ocean, in a
temperate climate, he would describe water as ‘a
liquid.’
26 The Ocean of Air.

If his first acquaintance with it were in the shape
of steam escaping from a boiler, he would describe it
as ‘a vapour,’ or as ‘a gas.’

He would not at once, without further observation,
know that these three are one and the same substance,
under different forms. He would not yet know that
ice can be turned into water, water into steam, steam
into water, and water into ice. Nor could he guess
that the Force which by its presence or absence works
these changes is Heat.

You have a solid block of ice, and a certain amount
of heat is brought to bear upon it. Gradually the ice
‘becomes water; and the solid has changed into a
liquid. But the substance isthe same. The particles
which form the water are the same which formed the
ice, only under altered conditions.

Again, more heat is brought to bear upon the water
until it boils. Then gradually it changes into steam ;
and the liquid has become a vapour. But still the
substance is the same. The particles which form the
steam are the identical particles which formed the
water, and before that the ice, only a change has come
over them.

If the steam is not allowed to escape, but is kept in
a confined space and cooled down, the particles will
draw together again, and the steam will once more
become water. If the cooling is continued, more heat
being taken away until the freezing-point is reached, it
will turn again to ice.

-To the same ice which it was originally! The
particles of matter are the same. The substance is
not altered. It has merely passed through a scries
of changes of form.

All solid substances are formed of minute particles,
The Weight and State of Air. 27

more or less closely bound together by a certain mutual
attractive power, which we call the Force of Cohesion.

Cohesion means ‘sticking together. When we
speak of the Force of Cohesion, we simply speak of the
Force of Sticking Together.

But to speak of the parts of a substance sticking
together is by no means to say why they stick together;
and to talk of the cause as a ‘force’ is not at all to
tell how it acts.

The ‘how’ of this matter is again beyond us; for
the attraction of cohesion is even more mysterious
than the attraction of gravitation. We see both by
their effects; but we do not know in what manner
those effects are brought about.

In a general way, when we speak of a ‘law’ we
mean a command which has to be obeyed. By a ‘law’
in Nature we mean rather a rule of action constantly
followed by certain bodies under certain conditions.
The word signifies, not that the Divine Ruler has given
definite commands which the world of matter obeys,
but that the Divine Creator has impressed or endued
each particle of matter with certain characteristics
which, under the same circumstances, always result in the
same modes of action or work.

We speak often of substances ‘obeying’ certain
‘laws;’ but since the word ‘ obey’ implies choice and
a possibility of disobedience, it is hardly a correct
term. Each particle of substance merely does in each
set of circumstances, and does inevitably, that which is
its nature to do.

But how and why one minute particle of matter
should differ so utterly in its nature from another is a
profound mystery.*

* Since writing these chapters, I have come across the following
28 : ‘The Ocean of Air.

In addition to the Force of Cohesion, which holds
together the particles of any substance, there is
another and opposite force, sometimes described as
the Force of Repulsion, or the Force of Driving
Away.

It seems singular that two such opposite forces
should be at work in one lump of iron or one piece of
wood ; that the very particles which are trying to get
closer to other particles should also be trying to get
farther from them. Many things in Nature are, how-
ever, brought about by such working of opposite
powers.

We are well able to see a need in the present
case for both, if our world is to remain in its present
form.

Without the force of cohesion there would be no
solid substances at all. The whole earth, and all it
contains, would be a scattered mass of loose im-
palpable dust, too fine for the human eye to see.
There would be no shapes or forms of separate bodies,
were it not for the force which binds their particles
together.

If, on the other hand, there were no check upon
cohesion, changes of an exactly opposite kind would
come about. The particles of each lesser substance
and of the earth itself would shrink closer and closer
together, till the entire mass would have grown in-
conceivably small and hard.

sentence in a letter of Charles Kingsley’s: ‘Everywhere, skin-

deep below our boasted science, we are brought up short by

mystery impalpable, and by the adamantine gates of transcendental

forces and incomprehensible laws, of which the Lord Who is both

God and Man alone holds the key, and alone can break the seal.’
* Lite of Kingsley,’ ii. 7.
The Weight and State of Air. 29

’ ‘This shrinking and hardening would include the
Ocean of Air. It is what we call ‘repulsion’ among
the air-particles which keeps them apart. If the
particles of any gas are forced closer together by cold
or pressure it becomes a liquid; if they are forced
still closer it changes into a solid. |

‘Probably all earthly substances are capable of
taking these three forms, under certain conditions,
though man has not always means at his command to
work the changes. There are solids which have not
yet been made liquid, and there are gases which remain
persistently gases. For a long while atmospheric air
resisted all efforts; but at length, under intense
pressure and cold, it was liquefied, and even rendered
solid.

So if no force of repulsion existed to counterbalance
the force of cohesion, not only would the whole Earth
become amazingly small and hard, but the whole Ocean
of Air would be transformed into a solid harder than
iron.

It is through the eanodite workings of these two
forces that we have the three forms BF matter—solid,
liquid, and gaseous.

In a solid, the cohesion is said to be eidsiee than
the repulsion. In a liquid, the cohesion and repulsion
are said to be equal. Ina gas, the repulsion is said to
be greater than the cohesion.

The particles of a gas struggle to get far apart one
from another. Unless confined on all sides, they fly
away and are lost. This would happen with our entire
atmosphere if it were not for the controlling power of
gravitation. The Ocean of Airis tied and bound to
earth by gravitation alone. In upper layers, where
both the attraction of the earth and the weight of the
30 The Ocean of Air.

overlying air are lessened, the separate air-particles
float much more widely apart; yet even there, even on
the outermost limits of the atmosphere, they are still
under the restraint of gravitation.

At the level of the sea, the atmosphere presses
upon each square inch of the ground, and of every
creature and thing upon earth, with a weight of about
fifteen pounds. The whole atmosphere all around the
whole earth is said to weigh a great many millions
of millions of tons. So really it is not astonishing
that the lower layers of air should be packed tightly
together.

It seems extraordinary that we do not ourselves fee!
the pressure, since it is upon us as well as upon the
earth. On each square inch of our bodies the atmo-
sphere bears hard with a force of about fifteen pounds’
weight, which means over two thousand pounds upon
the square foot, and something like thirty thousand
pounds upon the whole body of an ordinary-sized
man.

Try to lift a load of one hundred pounds; then
think what it would be to have twenty times that
weight lying upon your chest. You could only expect
to be crushed and killed.

Some such result would doubtless come about, but
for the fact that the pressure exists everywhere. Air
is not only outside but also inside us. It not only
surrounds, but pervades our frames. We, it is true,
are in the air, and no less truly the air is in us.
Pressure from without is counterbalanced by resistance
from within.

This fact of air-pressure can be shown byan ordinary
air-pump. Before the air is pumped out of the beli-
The Weight and State of Air. 31

shaped glass, it may be lifted by a finger; but when
the air is gone from within, the outside air bears
upon it so heavily as to make the glass immovable
under one’s utmost efforts. It is literally jammed down
upon the wooden stand. If the glass were not very
strong, and shaped for resistance, it would be shivered
to pieces.

Atmospheric pressure, acting equally in all direc-
tions, is due to its make asa gas. The particles of a
gas are in a state of ceaseless unrest, for ever hurrying
to and fro one among another with immense speed,
perpetually striking against each other and against the
sides of any vessel in which the gas may be confined.
Each particle of air is always ‘on the rush,’ always
striking and rebounding from its neighbours and any
solid or liquid substances which lie in its path.

If a tumbler is filled to the brim with water, and a
piece of blotting-paper or other soft paper is laid over
it, the glass may be carefully turned upside down, and
the whole body of water will be borne up by the wet
paper. That which keeps the paper in position is
neither more nor less than the ceaseless cannonade of
invisible air-particles—millions of millions of minute
pellets of air banging upwards each instant against the
paper from outside and holding it up.

It is this incessant battery of air-particles which con-
stitutes the pressure of air against the sides of a vessel
—upward, downward, within, without, and all ways. It
is this which, as above stated, when acting inside a
closed box or within the limits of the human frame, is
sufficient completely to counterbalance the outside pres-
sure. It is in this way—through the unceasing hail of
innumerable air-particles on the basin of a barometer—
that the mercury is held up in the barometer-tube.
32 The Ocean of Air.

The same explanation serves also for the rising 0
water in a pump.

Moreover, the degree of pressure varies at different
times and in different places.

A cubic foot of common air near the surface a the
earth generally weighs a little more than an ounce and
a quarter; in other words it generally presses with that
degree of force, not downward only, but in all directions.

Generally: not always.

The degree of pressure is proportional to the number
of air-particles within the cubic foot of air. The more
dense a certain portion of air is—that is to say, the
more closely its particles are packed together—the
heavier its pressure. Thus the weight of the atmo-
sphere generally, caused by gravitation, increases the
density of air near the surface of the Earth, and there-
by increases its pressure.

The amount of pressure is also increased by heat.
If a cubic foot of air is enclosed in a vessel of the same
size and is then heated, the pressure against the top,
bottom and sides of the inside of the vessel becomes
greater, because heat increases the energy of the air-
particles and so adds to the force of their battery.
CHAPTER IV.
AIR AS A MIXTURE.

Tue Air breathed by us and by all living creatures
upon earth is not a simple gas, but a mixture of gases.

Now, there are more ways than one in which
different substances can be mingled together.

You may put a lump of sugar into a cup of tea, and
stir well; the sugar vanishes, yet it is still there.
The separated particles float in the liquid, sweetening
it; though not seen, they may be tasted. No chemical
change has taken place, no real union of two substances
into one. The tea remains tea; the sugar remains
sugar.

Or you may mix together a small quantity of
powdered iron with powdered sulphur. Mixed thus,
they are not united. The iron is iron still; the sulphur
is sulphur still.

But push the mixed powder into a little heap, and
touch it with a lighted match. A red glow will creep
through the whole, and an entirely new black powder
will be the result; formed itself out of the iron and
sulphur, yet in itself neither iron nor sulphur but an
utterly different thing. The iron is gone; the sulphur
is gone ; and something else has sprung into being.

This is chemical change. It is the combining of
two or more separate substances into another and

3
34 The Ocean of Air.

different substance. It is not the mere mixing together
of two substances, which remain still the same that
they were before.

Every substance that we see or know is either Simple:
or Compound. If simple, it consists of one original
substance, which—so far as we at present know—can-
not be broken up into other substances. If compound,
it is formed out of the union of other substances, and
therefore it can by one mode or another be broken up.

Iron is a simple substance. A mass of pure iron
cannot be divided by the chemist into any other sub-
stances. It can be melted into a liquid, and trans-
formed into a gas; but the liquid and the gas are iron
still. Gold is another. It can be melted, and with
enough heat it might be vaporized; but the gold
always remains gold, undergoing no real change.

The chemist can split up or ‘analyze’ many things;
but when he comes to a simple substance, he has
reached a shut door, and can make no further advance.

It would not be safe to assert that all so-called
simple substances are absolutely simple. They may be
compound, though man has not yet discovered the fact.
But in relation to our knowledge they are, at least for
the present, simple.

Water is a compound substance. It is made of
two gases, oxygen and hydrogen The two gases,
separate, are each invisible. When united they are
seen and known as the liquid substance water, the solid
substance ice, the gaseous substance steam or vapour.

Simple Substances are also called Elementary Sub-
stances, or Elements. About sixty-seven are known.
A few among the sixty-seven are enormously abundant;
while others are scarcely ever met with.

They fill much the same place in the world of
Air as a Mixture. 35

matter as the alphabet fills in the world of litera-
ture. All words are made out of the letters of the
alphabet variously put together. All substances are
either simple—that is, they are single letters of the
alphabet—or else they are made up out of the simple
substances variously combined.

The Air of the Atmosphere is a simple mixture of
two simple substances, Nitrogen Gas and Oxygen Gas.

A mixture—not a chemical combination. The two
are mingled together much as tea and sugar are mingled,
floating in close companionship without becoming one.
No change has passed upon the nature of either; and
no third substance is formed. Each gas keeps its own
character.

Oxygen is rather heavier then nitrogen, so one would
expect the oxygen sometimes to sink, the nitrogen to
rise. But this is not the case. Almost invariably, air
is found to be a mixture of the two gases in the same
proportions. No doubt this is more or less due to the
ceaseless movements of air, the perpetual mixing by
winds.

Whether a portion of air is examined from a moun-
tain-top, from a level plain, or from a deep mine,
the mixture is almost exactly the same. Variations
there are, enough to tell upon man’s health, yet they
are at most extremely slight. The amount of nitrogen
in the air is always about four times as much by
measure * as the amount of oxygen.

If one should divide a certain quantity of air into
five almost equal parts, separating the two gases, one
part should be oxygen, four nitrogen.

* By measure, not by weight, since oxygen is the heaviest.
2-2
36 The Ocean of Air.

Or, to put it differently: suppose you have four
gallons of nitrogen gas, and you wish to transform it
into common air. You only have to add one gallon of
oxygen gas, and the thing is done.

Besides the two chief gases of which air is made, a
small quantity of Carbonic Acid Gas, and a still smaller
quantity of Ammonia Gas, are also to be found in it.

If you had ten thousand gallons of air, one fifth of
which would be oxygen, and four-fifths nitrogen: only
about one gallon of carbonic acid gas would be dis-
tributed thinly through the whole. As for ammonia
gas, only one gallon in amount is spread among one
million gallons of air.

So we can hardly speak of these two as having a
large share in the ‘make’ of the atmosphere. They
are rather a slight addition to it, a kind of ‘ flavouring,’
if one may so express it.

Yet carbonic acid gas, despite its comparatively
small amount, is of the greatest possible importance.
And indeed, though the quantity may seem slight,
viewed beside the other gases, it is by no means slight
as a whole. The entire mass of carbonic acid gas
always present in the Ocean of Air is simply enor-
mous.

Besides the gases, there is invariably more or less
water in the atmosphere, hidden away in the form
of Vapour. If you had one thousand gallons of air,
you would find spread through them from four to
sixteen gallons of invisible water-gas, or vapour.

The amount of carbonic acid gas and of water-
vapour is not constant, but varies incessantly at
different times and in different places.

There are also countless specks of matter floating
through the Air-Ocean, especially in its lower regions.
Air as a Mixture. 37

But the amount of these specks I cannot give in gallons.
Probably no one has ever even tried to reckon their
quantity.
We have now found in the air we breathe these

things :

Nitrogen Gas,

Oxygen Gas,

Carbonic Acid Gas,

Ammonia Gas,

Vapour of Water.

Floating Dust.
CHAPTER V.
AIR AS A PART OF EARTH.

Most people know that the Earth is not at rest, but is
in perpetual motion, spinning like a huge top, and also
rushing like an enormous ball round the sun.

I want you now to think steadily about the spinning
movement of Earth—about her daily whirl, top-like,
round and round upon her own axis.

If you stick a knitting-needle through an orange,
and spin the orange upon the knitting-needle, keeping
the needle itself fixed, this will help you to see the
‘ daily rotation’ of earth.

The earth is a huge globe, about eight thousand
miles straight through, from the north to the south
pole, or from the equator on one side to the equator on
the other side.

The movement of Earth’s surface as she spins is
very little indeed near the poles; while on the equator
the surface travels round at the rate of over one thou-
sand miles an hour. A man standing on the equatoris
carried along at that rate always, without the slightest
effort on his own part, borne onward irresistibly by the
rush of the solid ground on which he stands.

But suppose he gets into a balloon and rises into
the air—one, two, three miles upward—what happens
then?
Air as a Part of Earth. 39

Why, then, of course, as thé earth whirls away
from beneath him, he will be left behind, floating in the
still atmosphere. What more simple ?

Well, yes, it sounds very simple—a ‘most natural
answer. There was a time when it would have been
counted entirely correct. Yet the consequences of
such a state of things would be by no means simple.

We know a litile more about the matter now.

Suppose the balloon to start from the Island
Sumatra, exactly on the equator, to the south of Siam.
The solid’ ground there spins’ perpetually round the
centre of’ the earth, at the rate of one thousand miles
an hour.

The balloon rises upward in the calm air, on a still
day, towards the blue tropical sky.

As the surface of the earth below rushes from west
to east at this tremendous speed, more than fourteen
times as fast as the fastest express-train, you would
expect the man in the balloon to be left behind. I do
not mean that he would be blown by winds in any
particular direction, but merely that, as the earth
rushes away, the balloon would be stationary, floating
placidly at rest.

If this were the case, and the balloon‘¢ould remain
undisturbed by currents of air, the man would only
have to float reposefully in the same spot, and in the
course of twenty-four hours the whole circle of the
equator would pass beneath him. He would see in
succession the Indian Ocean, Africa, the Atlantic:
Ocean, South America, the 'Pacific- Ocean, and,. lastly,
the islands from which he started:: “A: wonderful ‘vista
indeed !

But ' practically a man’ in such'a ‘position has no
such magnificent diorama presented to-hims
40 The Ocean of Air.

He rises from Sumatra, and the earth’s surface
is spinning at the rate of one thousand miles an hour
—spinning along, but not spinning away. For as he
rises he looks down upon Sumatra still. If the air
were perfectly breezeless, he might rise to any height
at which he could breathe, and Sumatra still would lie
outspread below. If the wind were easterly, he would
find himself soon looking down on the Indian Ocean.
If the wind were westerly, he would travel towards the
Pacific Ocean.

The explanation lies in the fact that the atmo-
sphere is attached to the earth and whirls with the
earth.

Air, remember, is a material substance, not solid,
but formed of particles of matter. It is held fast to
earth by the force of gravitation. Each particle of air
has its share in the motion of the solid body to which
it belongs, to which it is tied by its own weight, that
weight being due to gravitation. Earth and Atmo-
sphere are practically one, and they act as one in the
daily whirl.

I do not say that there is no lagging behind of upper
layers of air anywhere upon earth. But taking the
matter generally, the entire atmosphere spins with the
spinning earth. The air in any one part has precisely
the same motion as the ground on or near which it
rests.

So a balloon or a bird in the air is carried with the
air in its daily rush around earth’s axis.

Imagine what the results would be if things were
otherwise, if the air remained fixed, while the surface
of the earth whirled away beneath.

We all know the effects of a high wind or a
hurricane. Now, wind is simply air in motion.
Air as a Part of Earth. 4I

If the air were utterly at rest, you may say that at
all events we could then have no wind.

But the effects of wind may be brought about in
two ways. One way is by the motion of air against
still objects; the other is by the motion of objects
through still air. Whether the air rushes fast against
a man, or whether a man rushes fast through the air,
makes no real difference. In either case the effect is
the same; in either case he is struck with the same
degree of force, by the resisting particles of air.

If the atmosphere were at rest, there would perhaps
not be a wind, strictly speaking. Nevertheless, if you
on the equator were careering at the rate of one
thousand miles an hour through still air, the effects
upon yourself would be precisely the same as if you
were at rest, and the wind were careering past you at
that rate.

A powerful hurricane travels at the rate of ninety
miles or more an hour, and the most solid buildings
often cannot stand against it. The heavy pressure of
air-particles, crowding one upon another in their frantic
rush, will level massive walls, tear off roofs, lay trees flat.

You may suppose, then, the destruction that would
be wrought by a hurricane blowing, not at the rate of
ninety milcs, but of one thousand miles an hour. The
results must prove equally overwhelming, whether
caused by the rush of air past us or by our rush through
the air; for in either case the fierce resistance of air-
particles would be the same.

A man standing on an engine going at the rate of
sixty miles an hour has a powerful wind in his face.
The air may be entirely still, no breeze stirring it, yet
his steady advance among the motionless air-particles
will cause him to have exactly the same sensations as
42 The Ocean of Air.

if he were at rest and a-strong gale were blowing.
To all intents and purposes it is a gale. The pressure
of air, resisting his passage, is in no whit different,
whether iis movement or its movement be the cause.

In the case that we have supposed of the solid
earth revolving while the atmosphere above remains at
rest, the resistance of the air in equatorial regions
would be tremendous, past imagination. Nothing
loose or movable on earth’s surface could stand.
against it.

Men and animals, trees and buildings, rocks and
stones, boats and ships—nay, the whole mass of ocean-
water itself—would be kept back by the enormous
pressure of the atmosphere, acting as a terrific hurri-
cane, and would be swept in one rushing pell-mell
torrent of ruin over the revolving surface of earth, in
the contrary direction to earth’s whirl. Complete
chaos and destruction could alone ensue.

This widespread destruction is prevented by the
simple fact that, as Earth whirls, her enfolding vesture
of air whirls with her. Practically, indeed, things not
only are so, but must be so. The atmosphere, weighted
by gravitation, clinging to earth, must move with the
earth. That the earth should revolve and the atmo-
sphere not revolve is an impossibility. The layer of air
lying close to earth’s surface is dragged round by the
earth, and drags round the layer above, which in its
turn does the same for the next, and so on, upward.
Or, rather, if the atmosphere were by any possibility at
rest, it would in this manner be speedily set going.
Once made to revolve, it is certain to go on revolving
until stopped by some other force.

Yet so calm, so soft, so steady is the motion,
despite its great speed, that we upon earth, carried.
Air as a@ Part of Earth. 43

smoothly along by the solid ground and the elastic* air,
are not conscious of it by sensation.

This same partaking of the motion of another body
may be seen on a smaller scale in common life.

Suppose a ship to be sailing over the sea, and a
man standing on the deck. That man is borne onward
by no exertion of his own. He remains perfectly still;
he makes no effort to advance. With relation to the
ship, though not with relation to the sea, he is at rest.
He does move, but only as a part of the ship, as sharer
in the ship’s motion.

A man seated in a train has a motion in common
with the train. As the train travels so he travels; and
so the air in the closed compartment travels. Outside,
the particles of still air strike the moving train with
sharp resistance; inside, both air and man are borne
along as part of the train.

The resistance of air-particles to any body passing
among them may appear a slight matter ; yet it works
a weighty part in the affairs of this world, not to speak
of other worlds, where also enfolding atmospheres
exist.

* Airis not only an elastic but also a viscous substance. An
elastic body yields for the moment to force, and springs back to its
original form when the force ceases to act. A viscous body yields
slowly to long-continued force ; but having yielded it retains its
new shape permanently ; and so long as the force continues to act,
it continues more and more to alter. Viscosity in a body implies a
certain amount of steady resistance to strain or pressure, with
gradual yielding to it, and lasting change of form in consequence.

There is some amount of elasticity in Air, and some amount of
viscosity also,
CHAPTER VI.
THE RESISTANCE OF AIR.

IF you draw your hand quickly through water you are
aware of a counter-pressure; the water seems trying
to hinder or push it back. A man swimming in the
sea or rowing a boat is keenly conscious of this.

The same resistance, though not to the same extent,
is found in the Ocean of Air. The particles of a gasare
less densely placed, less close together, than those of a
liquid; therefore a body moving in their midst can more
easily thrust them aside to make way for itself. Still,
there always is a measure of resistance.

This fact of Air-resistance is a serious item for con-
sideration in the matter of motion generally.

There are many bodies on earth at rest, and many
in motion. Those at rest have usually to move sooner
or later; those in motion come, as a rule, sooner or
later to rest. Two main rules govern the condition of
objects in motion or at rest. One is well known, the
other not so well known. They are these:

I. A body at rest is never set in motion except by
force.

II. A body in motion is never brought to rest except
by force. ,

The first of the two everybody will assent to at
once. We all know that a ball does not set itself
The Resistance of Air. 45

rolling; that a train will not start itself; that a cannon
cannot fire itself off. A certain amount of power or
force must be exerted upon a body from outside to
make it move, and it must always be enough force to
cause the particular movement required. A man’s
hand can throw or roll a ball of india-rubber, but a
man’s hand cannot start a train.

Even in the case of a man walking, though in a
sense he does set himself going, yet this only means
that his will takes the place of the outside force, and
causes his muscles to act.

But to say that a body in motion can only be
stopped by force—that is another matter !

Do we not all know that nothing on earth continues
moving for ever? Do we not all know that everything
inevitably stops sooner or later? Have we not seen
for ourselves how the swift cannon-ball, the whirling
grindstone, the spinning-top, the swinging pendulum, all
come to repose? Did not our ancestors search in vain
for ‘ perpetual motion,’ wasting time and money in a
hopeless quest, because no motion of bodies on earth
ever is perpetual ?

Yes, true enough, all this. Yet none the less true is
the rule given: motion is never stopped but by force.
No single body will ever move unless it is made to
move. Once set going it will never cease moving,
unless it is brought to rest by the exercise of a counter-
force.

For motion is as naturally permanent as rest!

Rather difficult to believe—is it nct ? Yet this is a
fundamental fact.

You see a big rock lying on a mountain-side, and
you are quite ready to assent, when somebody remarks
that the rock will not stir without being made to do so
46 The Ocean of Air.

There is a certain reluctance to change its present
condition, a stubbornness or inertia about the rock.
This inertia chains it to the spot where it lies, until
some outside force shall be exerted to set it
going.

But suppose such a force is exerted, and the great
rock is sent rolling, leaping, crashing, fiercely down the
steep mountain-side.

We have now a new state of things. The rock is
no longer at rest; it is in motion. The stubbornness,
the reluctance to change its present state, a state of
motion—the inertia, in short, of the rock—continue
as before, though manifested differently. Then the
rock was at rest, and it would not move without being
made to move. Now the rock is in motion, and it will
not stop without being made to stop.

Not stop! You are hardly so ready to assent to
this as to the former statement. Of course it will
stop, So soon as it reaches level ground!

Yes, of course. Concussion with the level ground
will prove to be a sufficient checking force. I did not
say that the rock would never cease to move. I only
said that it would not stop without the exercise of
force. No doubt a sufficient force will be exercised by
the resisting ground.

In this world there always is a sufficient checking
force to bring all moving bodies to rest. That fact
does not in the least detract from the truth of the _
opposite fact that, if no checking force existed, the
body would not cease to move. .

Take a tennis-ball in your hand, and fling it high.
That tennis-ball will go on for ever, unless stopped.

Fire a bullet from a rifle. That bullet will speed
onward for ever, unless stopped.
The. Resistance of Air. 47

Set a. grindstone whirling fast. That grindstone
will whirl for ever, unless stopped.

Make a top spin steadily. That top will spin for
ever, unless stopped.

These things always are stopped. But they do
not stop themselves; they do not come to rest of
themselves. Always, invariably, sufficient force is used
by something or somebody to bring them to a state of
repose. ;

The great checks to continued movement on earth
are commonly reckoned as two—Friction and the
Resistance of the Air. ;

These two may almost be reduced to one; for the
resistance of the air is really only a delicate form of
friction. It means simply the striking and rubbing of
the tiny particles of air against anything passing
through the midst of them.

The attraction of the earth is another great
hindrance to motion, but this also comes under the
head of friction. The earth draws the moving or
falling body downward; then friction against the
ground, rocks, or water, causes it to stop.

So by friction we mean the touching and rubbing
of other substances. If you touch a spinning top
ever so lightly with your finger, you will see at once
how great is the checking power of a touch to anything
in motion. Asa rule the word is used with reference
to solid bodies; but the resistance of water-particles
and air-particles practically amounts to the same
thing.

A great cannon-ball is despatched from the mouth
of a huge cannon, whizzing, whirling, tearing along,
ready to destroy aught that may lie in its path. The
48 The Ocean of Air.

force which has started the ball is the gunpowder
explosion, the sudden change of a solid into a gaseous
form, and the consequent tremendous pressure of
gaseous particles fighting to escape, thus overcoming
utterly the stubborn inertia of the ball at rest.

But when once the ball is off, some other force,
equal in degree, is needed to overcome the stubborn
inertia of the ball in motion, before it can be brought
to rest once more. Only, instead of being a single
sharp exercise of power, pent up in a tiny space and
in one moment, it may be a slow and continued
exercise of force, gradually acting.

If no such force is exerted, the ball will rush on
for ever, always in a straight line, always at the same
speed.

First the air-particles begin. It is wonderful to
think that such weak floating infinitesimal specks of
matter can have the smallest effect upon a mighty
cannon-ball. Perhaps you have never been underneath
a cannon-ball fired from a large gun, and so have not
heard the furious rush and whiz of its passage among
those air-particles, sounding like a small express-train
careering over your head. If you had, you would
realize that the opposition which they offer is by no
means contemptible. Singly they are soft and weak,
but banded together, acting in concert, they are
strong.

From the moment that the ball leaves the cannon .
they are at work. Each air-particle which lies in the
path of the ball, only to be fiercely thrust aside, only
to seem an utter failure, has done its tiny task. The
air-particles alone, unaided, would in time bring the
great ball to rest.

But something else is at work also, in conjunction
The Resistance of Air. 49

with the struggling particles of air. Earth is drag-
ging at the ball with her ceaseless pull. The force
of the explosion may send it far upward, yet soon the
pull of Earth tells, and a downward curve begins which
presently lands the ball upon the ground. For awhile
still it may leap and bound forward, but with every
crash of contact a further check is given, and at length
the moving body is at rest.

Yet, remember—the cannon-ball would never of
itself have travelled in a curved path or with slacken-
ing speed. It would have gone on interminably,
always straight forward, always at the same speed.
Without the resistance of the air, the attraction of the
earth, and the friction of the ground, it would not
have stopped.

So there was a sufficient cause for the starting of
the cannon-ball; there was a sufficient cause for its
moving in a bent path; there was a sufficient cause
for its going more slowly; there was a sufficient cause
for its coming to a standstill.

There is always a sufficient cause for every move-
ment, and for every change of movement, in a moving
body, just as much as for any movement at all in a
body hitherto at rest.

We thus see distinctly that it was the inertia of the
heavy cannon-ball which made a strong explosive force
needful to start it in swift career. Once started, it was
the very same inertia, differently shown, which made
the continued resistance of air and earth needful to
bring it to repose.

A curious calculation has been made illustrating
how great is the resistance of air-particles to a body
moving with great rapidity. A cannon-ball is fired off,
and travels, let us say, some six thousand feet before

4
50 The Ocean of Ain

touching the ground. If the air offered no resistance,
it would have sped to a distance of over twenty thou-
sand feet in one unbroken rush.*

The nearest approach to unceasing motion on earth
is to be found in a pendulum, hung in a vacuum from a
hard fine point. There, no soft elastic atmosphere
checks the steady swing. Nothing checks it, except a
very slight degree of friction at the point from which it
hangs. Still, some amount of rubbing always does
and must exist at that point. The pendulum may
swing for hours, even through a whole day, but sooner
or later it has to stop.

The only apparently perpetual motion, of which we
can speak with confidence, is that of the heavenly
bodies—the whirling and revolving suns and worlds.

Our Earth is one of those worlds. Her movements
have lasted through ages unchanged, since the Hand
of God sent her forth upon her celestial pathway.

How she was first set going we do not know; and
how long she will continue to move we do not know.
All we know is that sufficient force must have been
exerted to set her whirling and revolving; and that
no sufficient force has ever since been exerted to bring
her to a standstill.

In the wide regions of space no air exists to check
her movements. The Earth carries the Atmosphere
with her as she rolls onward; a soft surrounding
vesture; a deep translucent ocean; a very part of
herself. There is no vast Ocean of Air throughout
space. The stars and planets roll unhindered through
centuries of centuries, with calm continuous whirl.

Something, indeed, there probably is, though not
air, something unspeakably thinner and lighter than

* Todhunter.
The Resistance of Air. 51

our atmosphere, something so rare and fine that we
can scarcely more than guess at its existence. But if
this ‘something,’ which we call ‘ther,’ does indeed
extend through space, and can exercise any checking
force upon the heavenly bodies, it is a force so slight,
so slow in action, that no results are yet apparent. To
man, watching with dim eyes from the lower levels
of the Air-Ocean, the motions of suns and worlds
through thousands of years show no change.
PART II.
GASES OF THE AIR-OCEAN,

CHAPTER VII.
THE USES OF OXYGEN.

WE must now learn a little more about the separate
Gases which, mixed together, make our Ocean of Air.

Wherever Atmospheric Air is found, it consists, as
explained earlier, of about four-fifths by measure of
nitrogen to one of oxygen. Though the quantity of
nitrogen is so much greater than that of oxygen, yet
the oxygen may well claim our chief attention.

Oxygen is the great Life-supporting power on earth.
Without oxygen, plants could not grow. Without
oxygen, animals could not exist. Also, without oxygen,
fire could not burn. Nitrogen does little positive work
in comparison, but rather fills the humble office of a
make-weight and a drag upon the intense activity of
its companion.

One of the compounds of nitrogen, from which,
indeed, comes its name, is nitre. Another is nitrous
oxide, well known under its old name of ‘ laughing gas.’
If breathed under particular conditions it causes a
kind of intoxication, and when in that state men act in
a strange and laughable manner. It is now much used
by dentists, and also by surgeons in smaller surgical
cases for the deadening of pain. As its name tells, it
is formed of nitrogen and oxygen.

Nitrogen is found in the solid earth, as well as
56 . The Ocean of Air.

in the Ocean of Air. It has a share in the make of
plants and animals; no unimportant share in the case
of animals, for without nitrogen neither blood nor
muscle could be formed.

Pure nitrogen is colourless, tasteless, and scentless.
It is called ‘ inert,’ or slow and heavy, from its seeming
reluctance to unite with other substances. It does
unite with some, but not readily. Oxygen, on the
other hand, seems always to hold itself open to com-
bine as fast as possible with almost any other substance.

One might liken those two gases, with their very
opposite characteristics, to two opposite characters
often seen in men—the first, dull, slow, holding aloof
from other people, cautious and cold, rarely making
friends; the second, eager, sparkling, warm-hearted,
prepared to rush into enthusiastic friendship with
nearly anybody who may come in his way.

Nor is it difficult to understand how, if these two
lived and worked together, the slowness, caution, and
coldness of the one would act as a check upon the
eagerness of his impulsive companion,—just as nitrogen
does upon oxygen.

Suppose you have two closed jars, one full of pure
nitrogen gas, the other full of pure oxygen gas; and
also a little wax candle, like those which are used for
Christmas trees.

If you light the candle and lower it into the
nitrogen gas, not letting the gas escape and not letting
any air get in, the flame will at once go out. Butif you
put the lighted candle into the jar of oxygen gas, it
will burn much more quickly and brightly than in
common air.

Nitrogen gas cannot support combustion. In
common air oxygen does all that work, and nitrogen
The Uses of Oxygen.

Cae

7
only hinders it. Pure oxygen, apart from nitrogen, is
a tremendous quickener of fire.

Suppose, instead of putting a lighted candle into
either of the closed jars, you were to put a poor little
mouse into each? Jam not advising this act, for if
needless it would be cruel; but suppose it had to be
done.

The mouse in the nitrogen would quickly die of
suffocation. He would not be poisoned, for, strictly
speaking, nitrogen is not poisonous. The little creature
would simply die from lack of oxygen—would die
because the nitrogen is dull and powerless to do for
his little frame what is needed to keep it going.
Nitrogen can no more support life than it can support
fire.

The mouse placed in pure oxygen would not be
suffocated, but it too would die, though not so quickly,
of the too strong oxygen.

We all know the effects of a very strong pure alr—
that is, air which has rather more than the usual
quantity of oxygen. It excites and exhilarates the
whole frame.

To breathe perfectly pure oxygen for any length of
time would have the same effect, but in a very intense
degree. It would be an extreme case of what is called
‘over-stimulation.’ If our atmosphere could get rid of
all its nitrogen, ard consist of oxygen alone, the whole
of mankind would be speedily laid low or driven mad
with desperate fevers, burning away their strength.
And if any building in a town caught fire, the whole
town would be doomed, the flames spreading with such
ruthless fury that all efforts to check them would be in
vain.

Thus we find the need of the dull deadening nitrogen
58 The Ocean of Air.

to control the too exciting oxygen. The oxygen has,
in fact, to be weakened for our use, just as many a
strong medicine has to be diluted with water before
we can safely drink it.

Nitrogen gas has been changed by chemists to a
liquid, and even to a solid, described as ‘a snow-like
crystalline mass.’ Oxygen gas, also, has been liquefied,
and is capable of becoming a solid—in other words, of
being frozen. Both these are always gases on earth
in their natural state, great cold or great pressure
being needed to change their state. When either is
combined, however, with other substances, the result
is often a liquid or a solid.

Like nitrogen gas, oxygen is colourless, invisible,
tasteless and scentless.

There are enormous quantities of oxygen on Earth,
apart from what is constantly floating free in the Ocean
of Air.

The rocks of earth, piled often to mountainous
heights, are in their make, nearly one-half oxygen, by
weight. The stones, big and little, which lie scattered
by millions on earth’s surface, are in their make nearly
one-half oxygen by weight. The soils of earth, from
which sprout grasses, plants, and trees, are in their
make nearly one-half oxygen by weight. The waters.of
Earth—seas and rivers, ice-fields, clouds and vapour—
are in their make not only one-half, but eight-ninths,
oxygen by weight. And when we come to examine
the bodies of living things, both plants and animals,
we find them also to contain in their make a goodly
amount of oxygen.

In fact, if the whole of our solid globe were broken
up into all its ‘component parts’—that is, into the
separate substances of which it is composed—each
The Uses of Oxygen. 59

different substance being placed alone—the heaviest
supply of all would be the oxygen supply. Nearly one-
half, by weight, of the entire mass would be. pure
oxygen.

I say distinctly ‘by weight,’ and not ‘in size.’
Oxygen might be far the heaviest heap without being
the biggest. Many light substances take up more room
than heavy ones.

If you have a gallon of water, that water has in its
make eight times as much oxygen as hydrogen by
weight ; yet if the water is divided into the two gases,
it will be found that the hydrogen takes twice as much
room, or is twice as large, as the oxygen; for hydrogen
is light, and oxygen is heavy.

So we see that oxygen is one of the most important
elements on earth, and also that we have a very large
supply of it.

But if questioned what oxygen really is, 1 can omy
answer that it is, or appears to be, a simple substance.
It will unite with or separate from other substances;
yet in itself it remains unchanged. It can never be
broken up into other substances. Seeking to analyze
the make of oxygen, we come to one of those fast-shut
doors spoken of earlier. ‘Thus far,’ seems to be
uttered, and we can go no farther.

By-and-by, it is true, science may find a mode of
opening that closed door and getting through. If so,
the mystery will only be pushed a little farther back.
Another closed door is sure to lie not far behind. This
is always the case. With our present powers we never
do or can get to the end of anything, with no mystery
lying beyond. One might almost say that, if we could,
that would be the greatest mystery of all.
60 The Ocean of Air.

At present oxygen is—as to its real nature—a
shut door. We know of its existence; we see what it
does, and what it cannot do; we are acquainted with its
peculiar characteristics, its especial modes of action;
we are aware what to expect from oxygen in particular
circumstances. That is about all.

Oxygen is by no means stationary, fixed in certain
positions through countless ages. Portions of oxygen
may remain very long fixed in such solid bodies as
rocks and stones, though even they are subject to
waste. But oxygen in general is remarkable for its
activity, its love of change.

A perpetual intercourse is kept up between the
oxygen of the earth, of the sea, and of the air ; between
the oxygen of living creatures and of things without life.

Oxygen is for ever passing into structures and out

of them again; becoming part of organisms and leaving
them ; uniting with other elements, and breaking loose
from them; entering into the make of liquids, only to
separate itself anew; feeding flame, and life, and
_growth, but in the very act finding renewed freedom;
ready always to be, caught and ‘fixed’ by the next
substance which may come in its way under the right
conditions, yet seldom content to stay long in any
combination where escape is possible. Thus a cease-
less Circulation of Oxygen is kept up.

There are other circulation systems to be noticed
later. There is the Circulation of Blood in a living
animal; there is the Circulation of Air; there is the
Circulation of Water. But this Circulation of Oxygen
is not the least remarkable among them.

Almost all substances will unite with oxygen to
form fresh substances. These others, springing from
The Uses of Oxygen. 61

the union, are called Oxides, and the act of combining
is called Oxidation.

To cause such union, a certain amount of heat
must be brought to bear upon the different sub-
stances, and not always the same amount. Some
substances require more, some less, before they will
unite.

Whenever chemical combination takes place, under
the influence of heat, there is also a giving-off of heat
by the bodies as they unite.

This is an invariable rule, though the heat may not
always be felt or seen by us.

If the union takes place very slowly, as in the
forming of iron-rust, the heat given out will be gentle
and imperceptible. If the union takes place: fast,
as in the burning of a piece of wood, there will be
sensible warmth and a red glow, perhaps flame. If
the union takes place with extreme suddenness, as in
a gunpowder explosion, there will be great heat, a
bright flash of flame, and a loud noise.
CHAPTER VIII.
WHAT IS MEANT BY BURNING?

SOMETHING is meant by Burning which has a great deal
to do with the Ocean of Air around us. For if there
were no air, there could be no Combustion.

On a cold winter’s day we have a fire in the sitting-
room. The flames play about the coal, and gradually
the lumps of coal grow smaller, till they disappear. If
more coal is not heaped on in time, the fire goes
out.

What becomes of the coal ?

It is burnt, of course. Any child could answer that
question.

But what does ‘ being burnt’ mean?

Suppose we have an iron ball in the grate, lying
among the burning coals, to fill up some of the space.
This ball gets red-hot, like the coals, though it does
not, like them, send out flames. Heat is very ‘ catch-
ing,’ and passes readily from one object to another.

The iron ball seems to burn, like the coals; yet,
unlike the coals, it shows no tendency to disappear.
It does not even get perceptibly smaller. When the
fire dies out and the red-hot ball grows cool, it is seen
to be unchanged.

If the one burns and vanishes, why does the other
burn and not vanish ?
What is meant by Burning ? 63

This question is easily answered. The iron ball
does not burn. Some substances burn easily, and some
not easily. Some will burn at any time in common
air, and some only under particular circumstances.

Iron is a substance which will ‘stand fire.’ It can
be made red-hot or white-hot, melted, and even turned
into a gas; but it will not burn in common air.

So becoming red-hot or white-hot is not necessarily
the same as burning.

But though iron will not burn in air, it can be made
to burn—really to burn, lessen in size, and disappear—
like wood. If a piece of iron-wire is placed in a vessel
filled with pure oxygen gas, it can be set alight, and will
burn away as easily as a wooden match.

In the end of the last chapter I spoke of fast and
slow combining, and mentioned iron-rust as an example
of the slow combining.

Now, iron-rust simply comes from the union of iron
with oxygen—generally at a slow rate in a damp place
—and it is called Oxide of Iron.

But this same oxide of iron, or iron rust, can also
be produced quickly by burning a piece of iron in
oxygen gas, as above described. Then, again, the iron
unites with oxygen, and iron oxide, or rust, is formed.
Only, as the union takes place fast, much more heat is
given forth in a few seconds. The more rapidly heat is
sent out in burning, the more intense it is.

Whether the rust is formed fast or slowly, the
actual process is the same. It is Oxidation. We call
the one a case of ‘burning,’ and not the other; yet
the only real difference between the two is in respect
of temperature and speed. The common trusting of
iron in a damp place really is a species of very slow and
languid combustion.
64 The Ocean of Arr.

What becomes of the coal in the grate when it
burns and diminishes in size ?

The coal is divided, and goes three ways. Part
rises up the chimney as smoke or soot. Part falls
below as ashes. Part unites invisibly with oxygen
from the air, causing heat and flame in the act of union.

You have seen that iron can unite quickly with
oxygen by burning, as we usually understand the term,
only when it has to do with pure oxygen, unweakened
by nitrogen. But coal or wood, when sufficiently
heated, can take the oxygen out of the air, leaving
the nitrogen behind. So we say that they ‘burn
easily.’

If the fire has been allowed to get too low, and
fresh coal put on will not ‘catch,’ what then? Why,
then we use the bellows, and pour a supply of fresh air
in gentle streams upon the reddest spot remaining, in
the hope that a new and abundant supply of oxygen
gas will waken the half-dead embers and revive the
flame. The oxygen gas in the air lying close to the
coals has been pretty well used up, but a fresh supply
will give what is needed.

Coal alone, without oxygen gas, cannot give us
flame and heat. For oxygen is the great quickener
and supporter of fire.

If we could banish all the oxygen gas from the
room, keeping only nitrogen gas, any amount of paper,
wood, and coal might be put into the grate, and the
bellows might be used to any extent, yet to no avail.
The fire would at once die out. Nitrogen is powerless
to keep it alive.

So now we see the object of bellows to waken a

dying fire—just that a fresh supply of the needful
oxygen may be given.
What is meant by Burning ? 65

‘Wisdom is profitable to direct,’ saith the wisest
of kings. One cannot but remember these words,
when watching an uneducated maid puffing away at
a lump of black coal, without the slightest result. A
very little wisdom would teach her to direct the stream
of fresh air towards a ved spot, where alone it can take
effect.

If bellows could be so made as to feed the fire with
pure oxygen gas, then at any time the last spark of a
dying ember might be roused with ease into fresh
life.

Such bellows would also have a curious effect on
the red-hot iron ball. Under a steady play of oxygen
gas, the ball would begin to waste away like burning
coal.

When anything ‘burns,’ it not only gets red-hot, but
also there is a rapid loss of material. It grows smaller
and smaller, and almost or quite disappears. Either
part or the whole of its substance unites with the
oxygen of the air, and passes out of sight into the
atmosphere.

This is what we mean by a body ‘ burning,’ or being
‘in combustion.’

To make a body red-hot is enough often for com-
bustion, without flames. Where inflammable gas
exists—that is, a gas which will unite quickly with
oxygen—there will be flame. Usually, flame arises,
not from a solid or a liquid but from a gas in combus-
tion. When flames play round a burning lump of coal,
they are caused by the escaping hydrogen. Some sub-
stances will only grow red-hot and waste, but will not
show flame.

Any body intensely heated and glowing, yet not
lessening in size, losing weight, or uniting with oxygen,

5
66 The Ocean of Atr.

does not burn. The heated object is then said to be
‘ignited,’ or ‘incandescent,’ but not ‘in combustion.’

If a piece of magnesium wire is held in the flame of
a gas-burner it will take fire, burn brightly, and waste
away, growing shorter.

If a piece of coiled platinum wire is held in the
flame it will become hot and glow brightly, but there
will be no perceptible loss of material.

So the magnesium wire is said to be ‘in com-
bustion ;’ the platinum wire is said to be ‘in a state of
* incandescence.’

We see an instance of the latter in many of the
new electric lamps. A thread of carbon is shut up in
a glass bulb from which all air has been expelled, and
it is then made red or white hot by a stream of elec-
tricity. But it does not burn; it only glows. It
cannot burn, for there is no oxygen within reach, and
the ‘burning’ of a substance means its union with
oxygen.

Another instance is known to us in the glowing
gases which play fiercely over the sun. In common
speech we talk of the ‘burning’ surface of the sun;
yet the term is wrong. The gases which send out so
intense a glare are, it is believed, only glowing, not
burning. They give forth heat and light, but they do
not unite with oxygen and waste away. To speak of
flames on the sun is equally incorrect. Flame is gas
in combustion, and the gases of the sun are believed
to be only incandescent, not in combustion.

For true burning the presence of oxygen is generally
needful, and the presence of some other combustible
substance to combine with the oxygen is equally needful.

We can no more make a fire of oxygen without
What is meant by Burning ? 67°

coal than of coal without oxygen, for both are required.
Having both, we must bring them together, and must
place them under the touch of sufficient heat. When
this is done, and the union of the two is started, enough
heat will be given out for carrying on the work and for
warming the room.

In the lighting of an ordinary fire, heat is first ap-
plied by a lighted match to the paper or shavings.
Some of the paper or shaving substance at once unites
with a little oxygen in the air, and that act—the
breaking loose of particles from the solid substance to
join with particles of oxygen—causes a setting free of
fresh heat. This heat spreads to the wood, and another
union then takes place, particles of wood breaking
loose to form a combination with more oxygen.
Further heat is again given out, which spreads to the
coal, which in its turn catches fire, entering on a course
of union with the ever-ready oxygen. Thus heat both
causes and springs from combustion. Now, what of
the new substances formed by these various’ com-
binations ? é

The particular substance which is formed must de-
pend in each case upon the particular substance which
is burnt. As a matter of fact, in the common every-
day burnings around us, two especial substances are
by far the most common as the ‘second party’ in this
union. They are—Carbon and Hydrogen.

When a lump of coal is burnt, part goes up the
chimney as soot, part falls below as white ash, part
vanishes. So with the burning of a wax candle: part
passes away as soot, while the greater part slowly
disappears.

Yet, though the coal and the wax pass out of our

5—2
68 The Ocean of Air.

sight, their substance is not destroyed. So far as we
can tell, no matter once created is ever put out of
existence. "We cannot say that it never will be, for the
future of the Universe of Matter is utterly unknown to
us. But man has no power to destroy a particle of it.

True, he can by using the Forces of Nature break
up many materials, change their form, cause them to
vanish. Yet the vanished particles may reappear.
The old form may be restored. There is no real de-
struction of the tiniest atom.

In the case of burning coal or wax, each particle
exists still, afterwards, somewhere and in some shape.

Part of the coal drops below as white ash. This
is the mineral- substance which cannot burn. Part
escapes as soot, or unburnt carbon. The great mass
of the carbon, which is the chief portion of the coal,
unites itself with oxygen, and forms a new combination.
This new combination, called Carbonic Acid Gas, floats
away, invisible, joining the hot smoke in its passage up
the chimney. Meanwhile the hydrogen gas, held in
the coal, also joins itself to oxygen, causing bright
flames as it does so. The result of that union is-—
Water, in the form of vapour.

The same takes place in the burning of a cande.
Some of the carbon escapes as unburnt soot, while the
greater part unites itself to oxygen, and those two,
losing their separate individuality, pass away into the
air as carbonic acid gas. The hydrogen combines
with surrounding oxygen, and these also float off as
invisible vapour of water.

If a clear cold tumbler is held over a candle-flame
it will grow dim with fine moisture. This moisture is
some of the newly-made water, condensed into a tiny
dew by the chill of the glass.
What is meant by Burning ? 69

The bright light given out by a candle or gas flame
springs mainly from the glowing of fine carbon-points
which float within the flame. Whereany of the carbon
is within touch of the air, it unites with oxygen and goes
off as carbonic acid. Inside the body of the flame the
air has no access, and there the carbon-specks can only
glow. For lack of oxygen they cannot burn, and so
they pass away as smoke.

If the whole of the carbon contained in the wax
could be at once burnt up as the flame creeps down
the wick, there would be no smoke and very little light,
but there would be much more heat.

Hundreds of tons of coal are daily consumed in
every great English city, especially in winter. It is
a wonderful fact, if we consider what is meant by
‘burning.’ A mighty mass of solid black coal is in
twenty-four hours utterly disposed of by the soft
translucent air, not swept aside in one mighty hurri-
cane blast, but gently lifted particle by particle, carried
off, and hidden away by the busy oxygen.
CHAPTER IX.
THREE FORMS OF CARBON.

BEFORE going into the carbonic acid gas of the Atmo-
sphere, we must think a little about Carbon, from the
union of which with oxygen springs carbonic acid.

Carbon is another simple substance—another of
those mysterious shut doors, beyond which, at present,
we cannot pass. It cannot by any means yet dis-
covered be split up or divided into other substances.

We have had so far to do with simple substances,
which in their ordinary free state on earth are gases,
such as nitrogen and oxygen.

Carbon in its natural earthly state is a solid, and
not only so, but it is one of the most stubborn solids
known. For a long while it resisted all attempts to
thaw it into a liquid.

When united with other substances, carbon appears
in multifarious forms, the names of which are legion.
It is a most abundant material, and it enters enormously
into the make of all vegetable and animal bodies—of
all ‘organized’ bodies, or creatures with life.

Without carbon our earth would be an uninhabited
desert. Without carbon we should have no grass, no
plants, no corn, no trees. Without carbon we should
have no birds or beasts. Without carbon there could
be no men, as now constituted.
Three Forms of Carbon. 71

For ‘men are built up of carbon !’—of course, with
the addition of other ingredients. In charred wood,
charred meat, charred human flesh, the underlying
black carbon is plainly to be seen. If the wood, meat,
or flesh is entirely burnt up, then no carbon remains:
the whole has united with oxygen, and has vanished as
carbonic acid gas.

White loaf-sugar is a Compound Substance, being
formed of carbon and water, for sugar is a vegetable
product. If sulphuric acid or oil of vitriol is poured
upon thick sugar-syrup, the mass blackens and swells
upward into a large quantity of loose charcoal.

Carbon is abundant in many rocks, such as marble
and limestone; also in chalk, coral, and shells, which
are largely of animal make. But while all this
is true—while numberless forms of vegetable and
animal substance are composed in a great measure of
carbon—yet in its most pure form, free from combina-
tion with other substances, carbon appears mainly in
three distinct characters.

The first form of pure carbon is CHARCOAL.

Perfectly pure charcoal is not common, any more
than perfectly pure aught else in this world. Every-
thing gets mixed up more or less with other things;
but if wood is slowly burnt in a vessel nearly closed,
tolerably pure charcoal will remain.

A far more important form of carbon, very nearly
allied to wood-charcoal, though less pure, is COAL.

What the world would be without coal, we can
only imagine by looking back in fancy to those times
when coal had not been discovered. All modern life,
modern comforts, modern appliances, modern dis-
coveries, modern experiments and inventions, seem to
72 The Ocean of Air.

depend upon the existence of coal. Without coal,
unless something else should take its place, England
would sink back into a kind of semi-barbarism.

Coal is a form of carbon. It is made from wood,
which consists largely of carbon, since trees, like men,
are very much built up of carbon.

Coal-fields are the buried remains of mighty ancient
forests, and the structure of wood can often be traced
in a piece of coal.

But this structure has generally vanished; for a
change has passed over. the woody substance, trans-
forming it into the fossil substance called coal.

The change has been brought about by an under-
ground operation, which is in fact much the same as
that by which a log of wood is transformed into char-
coal, only in the one case the action has been very slow,
in the other it is quick. The transformation of those
buried forests into not very pure charcoal has really
been through a course of exceedingly slow combustion
or oxidation, spread out over ages. Coal is the charred
remains of a former vegetation.

Combustion, as we have seen, does not always
mean becoming red-hot; though it always means
some amount of union with oxygen.

Is it not wonderful that all this preparation of fuel
was going on through long ages, man never dreaming
of any such merciful provision for the future of his
race ?

So charcoal, coke, or coal, is one form of carbon in
its natural state.

The second form of pure or nearly pure carbon is
GRAPHITE or PLUMBAGO,
We all know graphite as blacklead—wrongly so
Three Forms of Carbon. ‘73

called—the soft black substance used in pencils,
curiously unlike hard porous charcoal or shining coal.
Graphite is found in granite rocks, and elsewhere
underground. It has other uses besides that of ‘lead’
for pencils, not needful to be considered here.

Charcoal and graphite are not so very startlingly
Opposite in appearance and character. But it is when
we come to the third form of carbon that we find
an astonishing difference.

The third form of pure carbon is DIAMOND.

Certainly, no one would ever dream at first sight
of putting the brilliant rare diamond under the same
head as common black charcoal and graphite.

Yet the three are the same, absolutely identical in
nature. Each is carbon; carbon in its natural free
state, uncombined, or very nearly so, with any other
substance. Unlike in colour, unlike in shape, unlike in
hardness, unlike, we should say, in every single parti-
cular—they are one in nature, formed of the same
simple substance.

So we see that—

Charcoal is Carbon ;
Plumbago is Carbon;
Diamond is Carbon.

If each of the three were formed of carbon united
with other materials, we should think nothing of it.
The extraordinary thing is, that. each of the three is
carbon only, carbon throughout.

How and under what conditions carbon takes that
peculiar form, becoming a translucent flashing gem,
we do not know. The formation of the diamond is
still a mystery. We can only assert that, as the black-
lead of a vencil is carbon, as lampblack is carbon, as
74 The Ocean of Air.

coke is carbon, as charcoal is carbon, so diamond is
carbon. Charcoal, plumbago, and diamond, however
unlike in appearance, are one in nature. They are all
three merely different developments of the one simple
substance—carbon.

Thus vast quantities of carbon are present on
earth; floating through the atmosphere in union with
oxygen as carbonic acid gas; lying underground in
rocks and coal; residing in the bodies of plants and
animals.

Moreover, as we shall see, a perpetual interchange
is kept up between the carbon of the atmosphere and
the carbon of living bodies dwelling in the Ocean of
Air. Carbon is incessantly passing from the air into
living structures, and out of those structures into the
air again. Nay, the very carbon which, ages ago,
passed into living forests of trees, is in these latter
days poured back into the atmosphere, whenever coal
is burnt.

So there is a Circulation of Carbon in the world, as
well as a Circulation of Oxygen; not less active, not
less constant, not less widely extended. The whirl-
pool of life and change knows no cessation.

By means of the spectroscope we know that this
same substance, Carbon, which is so abundant on earth,
exists also in the stars and comets of distant space.
CHAPTER xX.
THE PERILS OF CARBONIC ACID.

Cargonic Acip Gas is being perpetually made, per-
petually poured into the Atmosphere, and perpetually
broken up once more into the carbon and oxygen of
which it is formed.

The quantity of it present in the air at any one
time or place varies exceedingly.

At some times and in some places a much larger
supply is being made, and is sent floating through the
Air-Ocean than elsewhere, and on other days.

There are certain especial modes through which
this gas comes into existence.

Carbonic Acid Gas is found wherever any substance
burns which is partly made of carbon.

Part or the whole of that carbon unites itself, in the
act of burning, with some of the oxygen round about,
so forming carbonic acid gas.

One of the chief perils of a house on fire arises from
the above fact. The carbon of the great mass of
burning materials combines rapidly with oxygen, and
large quantities of carbonic acid gas are poured forth.
Many a human being, unable to escape, is mercifully
stifled by the deadly fumes, long before any flames can
reach him.
76 The Ocean of Air.

If a wind blows, so much the worse; for the moving
air brings constant fresh supplies of oxygen; and as
these sweep over the house, the making of carbonic acid
gas goes on the more rapidly. In common speech, the
wind ‘ fans the flames,’ and the house ‘ burns faster.’

When a haystack ora bonfire is alight, and we go
to the side where the wind bears down upon us, we are
speedily aware of the over-abundance of carbonic acid
gas. Whether or no we can tell its name, the fact is
apparent by the choking stifling rush which drives us
from the spot.

The same danger exists in the burning of a charcoal
brazier in a room which has no fireplace. Terrible risk
to life is involved here; for as the charcoal wastes, it
gradually unites with oxygen to make carbonic acid, and
this gas has no escape except into the air of the room.
Many a solitary being has gone to sleep in such a case,
enjoying the warmth, and has been stifled in his sleep,
never waking again.

A sad instance happened not many years ago in
Paris. A young English girl had gone there in quest of
work—a quest which long proved fruitless. Success at
last came ; and she went joyously to tell her friend, an
English clergyman, who had kindly helped in the search.
Returning to her lonely room, she lit a little charcoal
fire, feeling in delight that she might now indulge her-
self, and never dreaming of danger. Full of hope, the
poor girl went to bed, leaving no outlet for the deadly
gas; and when morning came a hasty messenger
summoned the clergyman. He arrived, only to finda
dead body lying in the small room. All had been over
hours before.

The danger is greater at night than in the day,
because one is taken unawares in unconsciousness,
The Perils of Carbonic Acid. 27

because, too, of the recumbent position of a sleeper.
Carbonic acid is a heavy gas, much heavier than oxygen
or nitrogen. Except when stirred up by air-currents,
it always sinks downward ; and it will remain so dis-
tinct from the other gases that the lower part of a
room may be full of it, while the upper part has com-
paratively pure air. Through this heaviness it can with
care be poured from one vessel to another.

Carbonic Acid Gas is made in the fermentation
of wine. The sugar contained in the grape-juice is
broken up by the fermenting process, and fresh sub-
stances are formed from it, one of those substances
being carbonic acid.

A rapid fermentation first takes place, the liquid
needing to be occasionally stirred up. For this purpose,
in olden days and in some countries it was customary
fora man to enter in bodily. The warmth of his frame
was supposed to be advantageous, by promoting quicker
fermentation. It was, however, a perilous business for
the man himself, on account of the large quantities of
carbonic acid gas escaping, and several lives were thus
lost at different times.

When the more rapid fermentation is over, the wine
is moved to other barrels, and the slow ‘ after-fermenta-
tion’ begins, lasting for months. Here,again, the same
danger attends those who have to visit the wine-vats.
As a rule, the escaping gas lies low, and a man may
walk safely upright, where his dog will fall senseless
and die; but if he stoops to care for the dog, he too
may be overpowered. Sometimes the gas collects and
rises to such a height as to imperil men also. Too
hasty an entrance into the place may mean no less than
death, and fatal results have come about not seldom.
78 The Ocean of Ain

The following memoranda are of a visit paid by my
Father to a brewery many years ago: .

‘I was taken over one of the largest breweries in
London, in company with friends. The thing that
struck me most was the large fermenting vat, of the
size and form of a small room, in which the fermenta-
tion of “wort” was proceeding at a rapid pace. The
liquor was some feet in depth, and on the surface of it
floated a dense body of clear bright carbonic acid gas,
which overflowed at the gangway where I was standing,
like a waterfall, some twelve or fifteen inchesdeep. On
looking upwards through the bright colourless gas-fall,
it was very curious to see the dingy dirty London air
resting upon its surface, and gently waving along when
set in motion by blowing or fanning.

‘I stooped down, and ventured to take a small breath
of the gas-fall, but I did not attempt to take a second.
It was like a sword passing down my throat.

‘Subsequently I inquired the cause of the pain
given by inhaling the carbonic acid gas given off by
fermentation, whereas that given off by burning char-
coal is only stifling in its effect. I was told that there
is no pain in inhaling dry carbonic acid gas, but when
mixed with damp it has the effect I experienced.’

Carbonic Acid Gas, formed by the burning of
coal, would, if we had no chimneys, be poured into
our rooms to the detriment of health, if not to the
destroying of life. Where a chimney fails to ‘draw
well,’ that is, when the upward draught is not sufficient
to carry away all the gas with the smoke, we are soon
conscious of stinging and choking sensations, ex-
tremely unpleasant in kind.

Long, long ago, English fireplaces boasted no
chimneys. The fire was made in the middle of the
The Perils of Carbonic Acid. 79

room, and the smoke and newly-formed gases had to
meander about till they found their way out through a
hole in the roof. But since glazed windows were in
those days unknown, the absence of chimneys
mattered less; for there would always be a plentiful
supply of pure air pouring in below. As cold air is
the heaviest, while hot air is light, the fresh cold in-
coming air would speedily drive upward and outward
the dangerous gas.

Most of us have felt more or less the ill effects of
burning gas in a closed room. Gas, like coal, con-
tains much carbon, and when it burns, supplies of
carbonic acid gas are being steadily poured into the
air. Unless there is a way of escape through open
door, window, or ventilator, the air of the room changes
' fast from good to bad.

Some people are very sensitive to this, suffering
even in the earlier stages from headache, faintness,
and other trying sensations, while some can endure
an extraordinary amount of bad air without being
aware of it. Sooner or later, however, the hardiest
and most insensitive frame must suffer, the condition
of things produced being one in a succession of stages
on the highroad towards suffocation.

Carbonic Acid Gas is found wherever living creatures
are. No need to say ‘ living creatures which are largely
made of carbon,’ for all living creatures are largely made
ofcarbon. From them is poured out a regular intermit-
tent stream of carbonic acid gas with every breath.

This is why a room containing human beings, if
no fresh air is allowed to enter, becomes close and un-
healthy. Burning gas would make matters worse by
hurrying on the evil. But without any burning gas;
or lamp, or candle, we have still the same result.
89 The Ocean of Air.

It is no rare spectacle to see a Church or a room
in cold weather, full of men and women, having every
door and window fast shut from dread of the slightest
draught. Elderly people and nervous people are often
afflicted with an almost morbid horror of moving air,
while they are placidly indifferent to poisonous air..
The state of things is curious but common.

Now, the air of any closed place, steadily breathed
by men or animals, becomes gradually transformed to
a slow poison ; nay, in time, to a quick poison, though
affairs are seldom allowed to go quite so far. People
are usually content to give themselves and_ their
children over-pale or over-flushed faces, sickly sensa-
tions, and bad headaches, without advancing to actual
suffocation.

We hear a great deal of ill-health among the poor,
of stunted frames, pallid cheeks, and constant suffering.
Of course, much of this in certain cases may be due to
scanty food or to overwork. But it is a grave question
how much of it is not owing to the habitual breathing
of air, which has been allowed to gain too large an
amount of carbonic acid gas, simply from the lack of
an opened window.

There is a wonderful carelessness among the poor
as to fresh air. True, the fresh air at their command
is not always of the purest; yet it is better than none.
Nor is it in town-alleys alone, but also in country
cottages, that windows are built up with plants, never
to be opened, and that frequent ‘airing’ of a room
is a thing unthought of.

It would be hardly fair, however, to speak of this
indifference as a characteristic of the poor only. There
are houses in a higher station of society, houses in-
habited by the cultivated and refined, where the window
The Perils of Carbonic Acsd. 81

rof a much-used sitting-room is closed before breakfast,
and is never opened again before night.

Naturally, by evening the air of that room has
grown into a most undesirable compound. The mix-
ture of little oxygen with much carbonic acid is
rendered not more pleasant by various floating vapours
and particles of matter, given off in the course of many
hours from the lungs and skin of each human being
present.

A sharp current of air between window and fire-
place, or window and door, would speedily expel them
all, bringing a sufficient supply of fresh oxygen. But,
no; that would be too much trouble; or nobody thinks
of it; or somebody might complain of cold. So the
unhealthy mixture has to be patiently breathed by the
unfortunate individuals assembled there. However,
as already said, many people are not sensitive.

In the space of twenty-four hours a man, not
‘especially exerting himself, takes into his system about
eighteen cubic feet of oxygen gas. He also gives off
from lungs and skin about the same amount of car-
-bonic acid gas.

Suppose a man were in a room seven feet high,
seven feet wide, and seven feet broad, shut up com-
pletely, with no opening to admit fresh air. The whole
mass of air in that little room would, in twenty-four
hours, have passed through his lungs. Of all the
oxygen originally held by the air, one quarter would
have disappeared, its place being filled by about the
‘same amount of carbonic acid gas.

Suppose no air were then admitted, but the same
state of things were continued for another twenty-four
hours. By that time half the oxygen present would
thave been exchanged for carbonic acid gas.
82 .° ° The Ocean of Air.

Following out the same idea, we may say that in
three days three-quarters of the oxygen would have
given place to carbonic acid gas; while in four days
the oxygen would be all gone, and only carbonic acid
mixed with nitrogen would remain.

Of course this experiment could never be really
tried, because long before the close the man must,
after great suffering, have died of suffocation. By
burning charcoal continuously in a shut room, from
which all fresh air is shut off, the result described
could be actually brought about; but through a man’s
breathing cnly the earlier stages are possible.

Not far from the middle of the last century, a
terrible deed was worked in Calcutta by the guards
of the so-called ‘Nabob’ Surajah Dowlah, upon his
English prisoners. No more awfully forcible illustra-
tion could be found of the desperate need for fresh
air to keep human beings alive.

The story may well be given in the vivid words of
Macaulay :

‘Then was committed that great crime, memorable
for its singular atrocity, memorable for the tremendous
retribution by which it was followed. The English
captives were left to the mercy of the guards, and the
guards determined to secure them for the night in the
prison of the garrison, a chamber known by the fearful
name of the Black Hole. Even for a single European
malefactor that dungeon would, in such a climate, have
been too close and narrow. The space was only
twenty feet square. The air-holes were small and
obstructed. “It was the summer solstice, the season
when the fierce heat of Bengal can scarcely be rendered
tolerable to natives of England by lofty halls and
by the constant waving of fans. The number of

u
The Perils of Carbonic Acid. 83

the prisoners was one hundred and forty-six. When
they were ordered to enter the cell, they imagined that
the soldiers were joking; and being in high spirits on
account of the promise of the Nabob to spare their
lives, they laughed and jested at the absurdity of the
notion. They soon discovered their mistake. They
expostulated; they entreated; but in vain. The
guards threatened to cut down all who hesitated. The
captives were driven into the cell at the point of the
sword, and the door was instantly shut and locked
upon them.

‘ Nothing in history or fiction . . . approaches the
horrors which were recounted by the few survivors
of that night. They cried for mercy. They strove to
burst the door. Holwell, who even in that extremity
retained some presence of mind, offered large bribes to
the gaolers. But the answer was that nothing could
be done without the Nabob’s orders, that the Nabob
was asleep, and that he would be angry if anybody
woke him.

‘Then the prisoners went mad with despair. They
trampled each other down, fought for the places at the
windows, fought for the pittance of water with which
the cruel mercy of the murderers mocked their agonies,
raved, prayed, blasphemed, implored the gaolers to
fire among them. The gaolers in the meantime held
lights to the bars, and shouted with laughter at the
frantic struggles of their victims. At length .the
tumult died away in low gaspings and moanings. The
day broke. The Nabob had slept off his debauch, and
permitted the door to be opened. But it was somé
time before the soldiers could make a lane for the
survivors, by piling up on each side the heaps of
corpses, on which the burning climate had already

6—2
84 , The Ocean of Air.

begun to do its loathsome work. When at length a
passage was made, twenty-three ghastly figures, such as
their own mothers would not have known, staggered
one by one out of the charnel-house. A pit was in-
stantly dug. The dead bodies, a hundred and twenty-
three in number, were flung into it promiscuously, and
covered up.’

Dead! for lack of air to keep them in life! The
small amount of air within, breathed by one hundred
and forty-six pairs of lungs, grew rapidly worse and
worse, aS oxygen gave place to carbonic acid; and
the small window-openings were blocked up by the
struggling mass of human beings, fighting in the agony
of gradual suffocation for one breath of air. The
marvel was, not that. one hundred and twenty-three
died, but that so many as twenty-three outlived the
horrors of that awful night.

Carbonic Acid Gas is found abundantly in many
coal-mines.

Everybody has heard of the terrible fire-damp and
choke-damp of mines, but many would be at a loss to
define the difference between the two.

‘Fire-damp,’ wrongly known among miners as
‘sulphur,’ is a gas made of carbon and hydrogen. It
contains no sulphur whatever; and the word ‘damp’
is a corruption of ‘dampf,’ the German for ‘ vapour.’
In many coal-mines, especially in many English ones,
large quantities of this gas often collect amid the coal-
seams, and when released by a stroke of the pick-axe
it flows out in streams.

By itself it is not a dangerous gas. It will burn, if
lighted, but quietly, with a blue flame. Once let it
become mixed, however, with a certain amount of
The Perils of Carbonic Acid. 85

common air, and it becomes at once tremendously
explosive.* If it comes in contact with any flame, an
explosion instantly follows, rending rocks, and dealing
death to miners within reach.

Usually there are many men in a mine, when such
an explosion takes place, beyond touch of the actual
flames; but though not burned to death, another
danger not less terrible awaits them, and this is from
the ‘ choke-damp,’ or ‘ after-damp.’

The gas called fire-damp is made, as we have seen,
of carbon and hydrogen. When that gas takes fire
and burns ina great outburst of flame, large quantities
of carbonic acid gas spring into being, through the
union of carbon with oxygen; and the dangerous
carbonic acid gas, or choke-damp, flows through the
passages, searching out the miners in their retreats.
If overtaken by it, they are soon overwhelmed. A few
breaths of the deadly gas, and they fall in uncon-
sciousness—unless speedily rescued, never again to
wake.

In the great Hartley Colliery disaster more than
two hundred men died of the ‘ choke-damp ’ who might
otherwise have escaped.

The coal-gas which we burn in our houses, though
not quite the same in make as the fire-damp of- mines,
is very like it in one respect. Coal-gas, properly
managed, is harmless enough; but when mixed with a
particular amount of atmospheric air, it becomes
explosive. If a little air gets into a gas-pipe, or if

* The ‘certain amount’ may be any quantity between four
times and sixteen times its own volume—whence the great neces-
sity for abundant air-circulation in mines. Much air mixed with
the fire-damp is safe, while a smaller quantity mixed with it -is
perilous in the extreme. By reason of this peril, safety-lamps are
used in many mines, and uncovered lights are not perinitted.
86 The Ocean of Air.

the gas escapes and mixes with air, there is likelihood
of an explosion.

Gas as used in private houses, under the control of
people who do not in the least understand it, is a
perpetual danger to mankind. The one real safeguard
lies in its unpleasant smell; for when gas escapes it
always makes its presence known. Still, even this is
not enough. Uneducated persons will take a candle or
light a match to examine the source of the odour—
about the maddest feat they can well perform. The
wonder is that more lives are not lost thus ; and, indeed,
gas-explosions on a small scale are by no means
uncommon.

Carbonic Acid Gas is found wherever volcanoes
exist and fiery underground forces are at work.

In such regions great outpourings of it are wont to
take place, alike from open craters, from springs of
water, and from casual cracks and splits in the earth.
Herein lies one peril of volcanic districts. A man,
carelessly approaching a crater, or leaning over an
open fissure, may be choked by the rising fumes,
while in no peril from flames or hot lava.

‘Miss Bird, describing the fiery lake of Kilauea,
writes: ‘At times the level of the lava in the pit
within a pit is so low, and the suffocating gases are
evolved in such enormous quantities, that travellers are
unable to see anything.’* And again, at a later date:
‘The whole region vibrated with the shock of. the fiery
surges. To stand there was “to snatch a perfect joy ”
out of a pain and terror which were unendurable. For
two or three minutes we kept going to the edge, seeing
the spectacle as with a flash, through half-closed eyes,

* “Six Months in the Sandwich Islands,’ ;
The Perils of Carbonic Acid. 87

and going back again; but a few trials, in which
-throats, nostrils, and eyes were irritated to torture by.
the acid gases, convinced us that it was unsafe to
attempt to remain by the lake, as the pain and gasping
for breath which followed each inhalation threatened
serious consequences.’

-The same abundance of escaping carbonic acid gas
is found near Vesuvius, Etna, and other volcanoes, and
also in the neighbourhood of extinct craters, in lands
where eruptions are no longer known.

Carbonic Acid Gas is found wherever decaying
herbage exists or dead bodies of animals lie.

The carbon, of which both plants and animals are
largely made, is given back to the atmosphere when
they decay. It unites with the oxygen of the air, and
again carbonic acid is formed—by a slower process,
indeed, than that of burning, but with consequences no
less deadly.

Herein lies one danger of living among or near
great masses of dying and dead vegetation. ‘The fall
of the leaf’ in a wooded country is counted unwhole-
some. Every fallen leaf, in its decay, sends forth a
little stream of carbonic acid gas, and the. many small
streams join to cause a serious total.

The evil would be greater yet, but for the busy
worms who work so hard, drawing the dead leaves
underground. There they decay still, but not in-
juriously, helping to form new mould to feed plant-
life, instead of helping to poison the atmosphere for
animals and men.

Still, despite all that the worms can do, a good deal
of unwholesomeness does exist in such places, even in
England. More markedly it is seen in the swampy
&3 ' ' The Ocean of Air.

lands round about tropical rivers, covered with luxuriant
vegetation.

Also the presence of dead bodies.in or near human
dwellings is a danger to life. Besides sending out
germs of disease, their decay produces a large amount
of this and other noxious gases.

Carbonic Acid Gas is the precise opposite of Oxygen
Gas. The latter is life-supporting; the former is life-
destroying.

Whether it is in any sense an active poison has
been questioned. If the amount of it in common air
is increased, and the amount of oxygen is increased im
the same proportion, the carbonic acid seems not to be
hurtful. So it appears that a man who dies from
breathing carbonic acid, like one who dies from
breathing nitrogen, dies, not from a poison, but from
a want. He dies, not because he has taken in too
much carbonic acid, but because he has not taken in
enough oxygen.

Under intense cold and pressure, carbonic acid can
be liquefied, and has even been solidified to ‘a light
snow-like substance.’ Generally, however, as it floats
in the Ocean of Air, we know the said substance only as
a gas.

In taste it is slightly acid.
CHAPTER XI.
WHAT IS MEANT BY BREATHING.

SOMETHING is meant by Breathing which has a very
close connection with the Atmosphere in which we
live. For if there were no air, how could any creatures
breathe ?

But before going into what is meant by breathing,
we must have a few words about the right balance
between exertion and food.

If a man takes an hour’s sharp walk, at the end
of the hour he is not in all respects the same as
when he started. He has lost weight. He has paid
away in active effort some of his substance, both solid
and liquid. The former has gone off in clouds of
carbonic acid gas, the latter in clouds of steam or
vapour. This loss of substance means a pressing need
of something very soon to take the place of that which
is gone,

So long as the furnace-fires of an engine burn, there
is a constant need of fresh coal to feed the flames.
Otherwise the fire will die out, and the engine must
come to a standstill.

So long as the fire of life burns in a man, there isa
constant need of fresh fuel to support it. Otherwise
life will fail, and the man must die.

While life lasts, perpetual waste goes on; but the
go The Ocean of Air.

rapidity of waste depends upon the amount of effort
and exertion used. An engine travelling at the rate of
sixty miles an hour uses up coal much faster than an
engine travelling at the rate of thirty miles an hour.

If the man had sat still in his chair, or had loitered
lazily about, there would still have been loss of sub-
stance, but not nearly so much as in his hour’s brisk
walk. If, instead of merely taking a brisk walk, he
had climbed fast up a steep mountain-side, the loss of
substance would have been yet greater.

Active exertion quickens the breathing, the heart’s
action, the circulation of the whole frame. It’ means
the more rapid using up of material, and the greater
need of fresh material in place of that which is used.

The same result would be brought about if the man
stood still and lifted a succession of heavy weights.
There would again be exertion, quickened waste, in-
creased need of renewal, as compared with when he
stands still and does nothing.

The supply of fresh material can come only in
three ways:

1. As Food.
2. As Drink.
3. As Air.

Every human being, every kind of animal, requires
these three, and requires them imperatively.. He
must have air always. He must have food and drink
at regular intervals.

Just so, the engine must have food and must have’
air to keep it going. If the carbon of the coal or the
oxygen of the air is cut shcert, then the engine-fires
die out.

Many people take too much food, and many others
take too much drink, for their requirements; while
What is meant by Breathing. or

some take too little food, and others too little drink.
With each human being there is a certain exact
amount of both needed ; just enough, in fact, to balance
the amount of exertion and of bodily waste. Less
exertion means less waste, and consequently less need
of renewed supplies. More exertion means more
waste, and consequently more need of renewed
supplies.

The food and the drink taken are too much if they
are not balanced by a sufficient amount of exertion
and of resulting waste. They are too little if not
enough to supply the amount of waste caused by
exertion. “ad

So, the more a man does, the faster he loses
substance, and the more food he requires to make up
for the waste of his frame. This rule is of course
modified by particular conditions in particular cases.
What seems a slight exertion to one person may be a
severe exertion to another; and certain states of illness
may induce as much waste as any amount of active
exertion.

The very same results are seen, strange to say, in
the matter of thought and brain-work* as in bodily
effort. The harder a man. thinks, and the more
intensely his brain is exerted, the greater is the
animal-waste, therefore the greater is the need of
sustenance.

* ‘Before leaving the subject of food, let me tell you that head-
work takes even more out of a man than hand-work. Many of
you who work with your hands look upon professional men, and
others who live by their brains, as little removed from idlers,
-“doing nothing but sitting and writing.” If you think so, let me
tell you you are mistaken—every thought which issues from the
brain uses up a portion of the brain’s tissue : this brain-tissue has

to be re-made by blood, and ‘the blood can only be re-made by
good nourishing food.’—Manchester Science Lectures. :
92 « The Ocean of Atr.

Now, the renewal of lost substance, the sustaining
of the fire of life, takes place, as already said, in three
ways; more strictly, by two modes:

I. Feeding.
2. Breathing.

The ‘food’ includes both kinds, solid and liquid.
Of these, too much or too little may very easily be
taken. But there is no fear of a man breathing too
much or too little air, since his body settles that
matter for him, independently of his own will. All
that his will can do in the matter is to choose a place
where he is surrounded by good air, containing enough
oxygen and not too much carbonic acid.

Everybody breathes as a matter of course, not at
all as a matter of choice. Men breathe, beasts
breathe, birds breathe, insects breathe, whales and
porpoises breathe. Even fishes breathe, and breathe
air containing oxygen, though they get it out of the
ocean of water in which they live, and do not need,
like whales and porpoises, to come to the surface.

_ That a man cannot live without breathing is patent
to everybody. He may cease eating or drinking for
awhile, even. for days, though not without much
suffering. He cannot cease breathing for more than a
few minutes at the most, or he will die.

As he moves to and fro, on the floor of the Air-
Ocean, he draws every few seconds into his lungs a
certain amount of air, and as regularly sends at least
a portion of it out again.

This we know for ourselves from actual experience.
We may not be able to explain how or why we breathe,
but that we do breathe and must breathe we know
well, There are many things in this world which we
What ts meant by Breathing. 93

feel to be true, with a knowledge which amounts to
absolute certainty, while yet we are not in the least
able to explain why they are so, or from what causes
they spring.

Even the lower animals are aware of the need of
air. An experiment was once tried of putting a cat
into an air-pump enclosure, and pumping out the air.
Poor pussy felt it going, and she had the sense to try
to cover with her little paw the hole through which
the air was withdrawn, seeking thus to hinder the
escape of any more.

It is to be hoped that those who tried the experi-
ment were content with so much, and did not put her
to further needless suffering.

Of course the cat could not have told why she
needed the air, or by what particular process the air,
entering her lungs, kept her in life and health. She
only knew her own need, and knew what would meet
that need. Without any theories and without any
definitions, she was aware—and many human beings,
no wiser scientifically than was pussy, are aware too—
that not to have air for breathing means death. Some
higher needs of our nature are, after the same mode,
felt and met, without clear understanding on our part
either of exactly what need we feel, why we feel it, or
how that need is supplied.

A grown-up man of full ordinary height and size,
sitting still, breathes on an average about eighteen
times each minute. If he walks fast, still more if he
runs, mounts a steep hill, or lifts a heavy weight, his
breathing is quickened.

‘Each time that he breathes he draws into his chest
‘about twenty cubic inches of air—perhaps somewhere
94 The Ocean of Air.

about three-quarters of a pint—and sends out again
almost as much.

In so doing he does not empty his lungs, for the
lungs of a man contain usually between one and two
quarts of air. The whole amount is undergoing change
constantly but gradually, and not at every breath,
since a good deal of air always remains behind.

Now, the air which a man breathes out is markedly
different from the air which he breathes in. There are
four main points of difference:

It is much hotter;

It is much damper ;

It contains much less oxygen ;

It contains much more carbonic acid.

The day may be ever so cold, the water may be
frozen into ice, the ground may be hard, the air that he
breathes in may be down in temperature as low as the
freezing-point. All this makes no difference. The air
which he breathes out will be up to nearly 98°, or
almost as hot as his blood—cppressive summer heat.

The day may be ever so sultry, the ground may be
caked and hard, little moisture may be floating in the
atmosphere, the air breathed in may be dry as air can
be. All this, again, makes no difference. The air
breathed out will be soaked with vapour of water,
turning rapidly in the cold outside air to a little fog of
visible water-droplets. Does not a child know this
when he:breathes on his slate, that he may be able to
rub out faulty figures?

In the course of twenty-four hours nearly half a pint
of water is commonly given off from a man’s lungs,
but the amount varies much. ;
_ Whatever the day may be—hot or cold, dry or
damp—the air breathed into a man’s lungs is simple
What.is meant by Breathing. 95

atmospheric air. It is the usual mixture of oxygen
and nitrogen, with a slight addition of water-gas, and
so minute an amount of carbonic acid as to be hardly
worth thinking about.

But when the air is poured out again from the
lungs an extraordinary change has passed upon it.

The quantity of nitrogen alone is almost unchanged.
The quantity of oxygen has run down to only a little
over three-quarters as much as it was. The quantity
of carbonic acid has shot up to almost one-quarter of
the former amount of oxygen. In other words, the
lost oxygen is pretty well replaced by carbonic acid.*

Where has the oxygen gone? and where has the
carbonic acid come from ?

The answer is very simple. It is a case of Com-
bustion.

When a lump of coal or-a candle burns, do yo
remember what happens ?

There is a waste of substance. There is a giving
forth of heat. The hydrogen in the coal or wax unites
with oxygen from the air, and makes vapour of water.
The carbon in the coal or wax unites with oxygen from
the air, and makes carbonic acid gas.

That is a case of combustion—of rapid burning.

Combustion is not always rapid. It may be very
gradual indeed, as we have seen in the case of coal-fields.
‘There buried forests of trees weré slowly transformed

* Ifa pint of air, as breathed zm, were divided into ten thousand
tiny equal portions, the gases being separated, nearly eight thousand
of them would be nitrogen, more than two thousand would be
oxygen, and only three would be carbonic acid—a pint of air being

-not very much more than the quantity drawn in bya largeman. The
same amount, breathed ov¢, would contain about the same amount
as before of nitrogen ; only about fifteen hundred portions of oxygen ;
‘some four hundred and seventy portions of carbonic acid gas;
‘sand a greatly increased amount of water-vapour. .
96 The Ocean of Air.

by a kind of underground combustion into a species of
charcoal.

In the case of a man we have slow combustion
again; not nearly so slow as the combustion of buried
forests, but not nearly so fast as the combustion of a
burning candle or piece of coal. It is rapid enough
for the giving off of a great deal of heat, which heat
is borne by rushing streams of blood to all parts of the
body. It is not rapid enough for the burning parts to
become red-hot.

Combustion is—or «at least includes—the union
under a certain degrec of heat of a substance, such as
carbon, with the oxygen of the air.

That is just what goes on night and day in the
body of every man, woman, and child living, not to
speak of lower creatures. The carbon of which they
are largely made unites perpetually with oxygen drawn
into the lungs by breathing, and the two united are
given off as carbonic acid gas.

In the burning of a piece of wood the carbon of the
wood is needful, also the oxygen of the air, also enough
heat to cause their union.

In the slower combustion of a man’s body these
three are equally needed—the carbon of his body, the
oxygen of the air, and sufficient heat to make them
combine.

Something else is necessary also. Before burning
can begin, the carbon and oxygen must touch, and the
heat which is applied must reach them both at the
point of contact.

We see easily how this comes about in the matter
of a burning candle or lump of coal. The air flows
over and around, so that fresh particles of oxygen
are constantly running against particles of carbon in
What is meant by Breathing. 97

the wax or the coal, while heat spreads to other
parts.

But in the case of animal combustion the matter is
not so simple. The mass of carbon helping to compose
a man’s body is chiefly inside him, and the mass of
oxygen in the air is chiefly outside him. So how are
the two to come together? and how is sufficient heat
to be brought to bear ?

With regard to the heat one can say little. The
high steady temperature of a man’s frame is still in
great measure a mystery, partly accounted for by the
combustion always going on within that frame, but
connected with the greatest mystery of all—the Life
which reigns there.

It is easy to see that, the right measure of heat
once given, the combustion once started, burning will
go steadily on, whether in a fire of coal or in the fire of
a man’s body, so long as favourable conditions last.
That is to say, it will continue until either the supply of
fuel—of food—or the supply of oxygen shall run short.

But how the fire which set that combustion going
in man was first applied is another question. I know
no answer to it except in words familiar to us from
infancy :

‘God breathed into his nostrils the Breath of Life,
and man became a living soul.’

Now about the needful contact of carbon and
oxygen in a man’s body.

More than one great and world-wide Circulation has
been spoken of in earlier chapters.

In the frame of a man we have a yet more wonderful
Circulation, though on a smaller scale than that of gases.
It is more wonderful than the circulation of any mere

7
98 - The Ocean of Air.

material substances, for this is a circulation on which
life hangs.

Night and day, day and night it goes on; hour by
hour, minute by minute it continues. Rivers of blood
rush at full speed through the larger vessels of a man’s
body, thence dividing into smaller streams. These
career through lesser vessels, subdividing again and yet
again, till the tiny capillaries, the most minute vessels
of all, countless in number and reaching everywhere,
are filled with infinitesimal rivulets. From the capil-
laries the streams meet, converging into larger and yet
larger vessels, till once more they reach their starting-
point and begin the round anew.

Through all the round, as the stream flows onward,
it is incessantly leaving part of itself behind, and in-
cessantly taking up something new on its way.

Two kinds of vessels carry the blood; these are
called Arteries and Veins.

The arteries bear blood away from the heart; the
veins bear it back to the heart.

The arteries contain bright scarlet blood; the veins
contain dark purplish blood, often called ‘ black blood.’

Between the two kinds there is a marked difference.
In most respects, except colouring, they are much alike
as to make. In one respect they are gravely unlike.
The red blood of the arteries has in it plenty of oxygen
and very little carbonic acid; the purple blood of the
veins has in it.much less oxygen and much more
carbonic acid.

When the stream starts from the heart it is red and
pure; but as it passes through different parts of the
body it incessantly parts with its oxygen for the needs
of the body... Not only this. It incessantly takes up
and carries away useless particles of matter—waste
What is meant by Breathing. 99

materials no longer needed there. So gradually the
pure red blood loses its purity and brightness, getting
overloaded with carbonic acid and other hurtful matters.
By the time it has worked its way back through the
veins to nearly its starting-point, it is in dire need of
being charged anew with oxygen.

But—how?

By being brought into touch with the outside
atmosphere ; taking therefrom new supplies of oxygen,
and giving off superfluous supplies of carbonic acid.

A certain amount of this has taken place already.
Wherever tiny streams have flowed in minute vessels
close under the outer skin of the body, where the air
could reach them, there carbonic acid has been given
off. But much more is required,—is indeed an absolute
necessity. If the dark blood flow again and again
through the man’s body, he must die.

The blackened stream reaches the lungs, and is
there spread out over a wonderful network of tiny
vessels, all enclosed in a skin so delicate that air can
pass through it without the least difficulty. And

Why, then, those tiny vessels are met by pure air
from outside, atmospheric air, laden with oxygen,
rushing in with every breath. Each breath drawn in
brings fresh supplies of oxygen, and each breath poured
out gets rid of new supplies of dangerous carbonic acid.

So very soon the blood is sent careering on its
way, no longer purple but bright red, no longer
laden with bad materials but full of good gas.
Once more it hastens through the man’s frame,
leaving more oxygen on the road, carrying away
more evil things, which, if left, must endanger the
man’s life.

7—2
100 The Ocean of Air.

Now, what is the direct object of all this oxygen?
Why such constant supplies of it, carried into the lungs
by breathing, borne from the lungs by the blood to all
parts of the system?

To support combustion! Simply that! The man
is slowly burning! If he is to live, he must burn.
Combustion is life. Stagnation is death. So long as
the fires are kept alive in him he lives.. Let them die
out, and he dies.

Combustion means the union of oxygen with other
substances : for instance, with carbon to make carbonic
acid gas; with hydrogen to make water-gas. Both
these processes go on constantly inside a man.

Burning means burning away, not simply glowing
with a changeless heat. Man burns away as distinctly
as a candle burns away. The more energetically he
lives, the faster he burns away, and the greater his
need for fresh air and food.

‘If food ceases he dies soon; if air ceases he dies
immediately. Whatever else he has or has not, he
must have sufficient .air perpetually to overmaster and
carry off the superfluous carbon of his body. Other-
wise the carbonic acid will speedily overpower him.
Second in importance to this is the keeping of a just
balance between exertion and food. The more exer-
tion the better, so long as the amount. of waste can be
always and steadily sepaned.

Life means the putting forth of energy, of pais of
force; life means incessant waste and _ incessant
renewal; life mcans perpetual circulation and _ per-
petual need of fresh purification ; life means unceasing
combustion.

By which I mean simply animal life, the life of the
body. There is a Life above this, which does not
What is meant by Breathing. IOI

depend on movements of gases, liquids, and solids,
within and without the human frame.

Yet even in the higher spirit-life of man it seems -
as if much the same laws prevailed. There, too, stag-
nation means decay; absence of energy means death.
There, too, without circulation, without perpetual
renewal, without incessant taking in and giving out,
a healthy existence is-not possible. ,
CHAPTER XII.
HOW PLANTS WORK

But if, from the burning of every substance which
contains carbon, if, from the breathing of every creature
which has life, streams of Carbonic Acid are being per-
petually poured into the atmosphere, how is it that the
whole Ocean of Air has not by this time become unfit
for mankind ?

A room filled with people and having no outlet
would after awhile be incapable of supporting life.
What should prevent the entire atmosphere, once a
healthy mixture of gases, from changing in the course
of ages to a noxious and deadly mixture ?

There are enormous quantities of carbon upon
earth. If this great mass of carbon, through burning
by fire, through breathing of animals, through decay of
dead vegetation and dead bodies, became gradually
united to yet greater masses of oxygen drawn from the
air, and remained permanently in that condition, what
other result could follow ?

Exactly that which takes place in a fast-shut room,
containing an open pan of burning charcoal and no
chimney—exactly that would take place with the Ocean
of Air.

The amount of oxygen would grow steadily less and
less, the amount of carbonic acid would grow steadily
How Planis Work. 103

more and more, till all living creatures on earth would
die of suffocation.

Things would inevitably be so, but for the antidote
provided.

This antidote is found in the Green Vegetation of
Earth.

Plant-existence is not less wonderful, nor less
mysterious, than animal existence, though different in
kind.

Plants live, grow, take in food, give out vapour,
breathe, digest, even work and sleep alternately, as
animals do, only not after the same modes.

A plant can no more live and grow, can no more
keep in health and do its rightful tasks, without a suffi-
cient supply of light, of air, and of food, than a man
can.

Plants—by which I mean grasses, herbs, shrubs, and
trees, as well as all small garden and field plants—are
fed in more ways than one.

Through their roots they suck up liquid out of the
earth. Not pure water, but water containing many
different kinds of substance in the liquid form, drawn
by the water from various kinds of earth through which
it has filtered.

This liquid food passes slowly upwards through the
slender channels of the stem or trunk, spreading through
countless tinier vessels—like the capillaries in a man’s
body—till it reaches the minute veins of the leaves.

There much the same takes place with the sap of
the plant, as we have seen to take place with the blood
of a man on reaching the vessels in his lungs or close
to his skin. It flowsin little vessels made of so thin
and delicate a membrane that gas can easily pass
104 The Ocean of Air.

through, and thus the sap comes into contact with the
outer air. But sap is exposed to light as well. as to air,
which is not the case in a man’s lungs.

The leaves of a tree are often and justly called ‘ the
lungs of a tree.’

In some way a strange change is worked in the
sap when it reaches the green leaves; or, probably,
this change has begun in its upward passage througa
the stem and branches, to be perfected in the leaves.

A change of some sort always, but by no means
always the same change.

For when the sap has passed through the tiny leaf
veins, and slowly returns into the twigs, the boughs,
and the trunk, travelling downward, it is no longer the
same liquid that first rose from the roots into the stem,
travelling upward. What it has become depends upon
the kind of tree.

In one tree or plant the sap has become sweet like
sugar ; in another it has become acid; in another sticky
like gum. . In one it is wholesome and good for food ;
in another it is rank poison.

How these different results are brought about no
man can explain to us. We do not even know what
causes the sap to rise upward through the tubes of a
tall tree. Still less can we describe the manner of its
transformation into such different liquids.

Some plants will grow in certain soils, and will not
grow in others, doubtless because the particular food
that they need is not to be sucked out of all soils.
Each particular kind of tree, wherever it may grow,
always produces—or secretes, as it 1s called-—the same
particular kind of sap or juice. The deadly night-
shade can never, in any soil or climate, be made to
secrete harmless. sugar-juice. The orange-tree can
How Plants Work. ToS

never be induced to secrete lemon-juice. The gum-
tree can never be trained to secrete aught else but
gum.

The mysterious power which we call L1FE domi-
nates the whole existence of the plant. It controls the
form and manner of growth, forces the rejection of
some materials and the choice of others, uses the
selected materials after a definite mode.

How and why each plant should follow its own mode,
not some other mode, it is impossible to say. Certain
characteristics are stamped upon its being, and it acts
in accordance with those characteristics. That is all
we know; and that is no explanation.

The gardener may modify these natural tendencies
by training; but the gardener’s power is limited. Do
what he will, the deadly nightshade is deadly night-
shade still, and the orange-tree never becomes a fig-tree.

Plants have another mode of taking in food, as well
as through the roots. This is through the leaves.

The leaves are not only a perfect laboratory, with
the most delicate appliances for the manufacture of
various juices out of crude material. In addition to
this they have another work to carry out, a work of
world-wide importance to the human race. They have
to act as the antidote of which I have spoken. They
have to undo that which men and beasts and burning
substances are always doing on earth.

The leaves of a plant or tree have an extraordinary
power of sucking carbonic acid gas out of the atmo-
sphere, and drawing it into themselves for the use of the
plant.

It is an.absolute necessity that every plant and tree
Should have a certain amount of carbon from some-
Where, for growing purposes.. Plants, like men, are
106 The Ocean of Av.

‘built up of carbon.’ Some may be obtained through
their roots out of the earth, but by far the greater part
is gained by the leaves straight from the air.

For men as for plants carbon isa necessity of growth.
But a man cannot receive it straight from the air. He
gets his share in quite anther way—through those very
plants which have first secured and made it ready,
fitting it for his use. Every time a man feeds upon
vegetable food, or upon animals which have fed upon
vegetable food, he takes into his frame carbon prepared
by plants for his use.*

You have seen already that animals do in breathing
exactly what is done by burning coal or wood. They
carry on a work called oxidation. They unite some of
the carbon in themselves to some of the oxygen out of
the air, at a certain degree of heat, and send forth
streams of carbonic acid gas.

The plants of earth, large and small, by means of
their delicate green leaves, do precisely the opposite of
this.

They seize upon the carbonic acid gas which, ever
growing in amount, threatens in time to fill the Air-
Ocean and stifle every living creature. By some
mysterious means, helped by the sunlight, they
separate the carbon and the oxygen of which it is
made. They hold the carbon fast, and send it down
little channels for the use of the growing plants.
Lastly, they pour back into the atmosphere the pure
life-supporting oxygen, broken loose from its union with

* ©Plants, therefore, are the ‘“‘ hewers of wood and drawers of
water” for other living things. And this property, which they so
largely possess, of constructing, from materials not directly avail-
able for animal nutrition, substances which are so, is found to be
uniformly attended with the presence of a peculiar green colouring
matter known as chlorophyll..—Huxley and Dyer: Encyc. Brit.
How Plants Work. 107

the carbon, and once more fit to be breathed by
man.

See what an extraordinary contrast between animals
and plants.

Suppose you have a shut room, containing several
people, and containing also in a bow-window, where
the sun shines brightly, a mass of plants.

Each person there is stealing oxygen, from the air,
and sending out streams of carbonic acid, as fast as he
can.

- Each plant there is taking in carbonic acid from the
air, and sending out streams of oxygen, as fast as it can.

So the man undoes the work of the plant, and the
plant undoes the work of the man, each counteracting
the other.

If you have exactly the right number of plants to
balance the people present, if the plants are all ina
healthy condition, and if there is plenty of sunlight,
then there is no fear that the air of the room will become
too full of carbonic acid gas. For just as fast as the
people breathe it out, the plants will take it in, supply-
ing its place with oxygen gas.

But such a balance could only be secured in day-
time. The leaves have no power to carry on the work
of which I am telling, except with the help of sunlight.

So markedly is this the case, that plants are some-
times said to be ‘made of carbon and sunlight;’ and
when coal is burnt, it is said to be giving out in heat
the bottled-up sunlight of past ages.

Not long ago it was customary to say that plants
‘breathed’ in a mode exactly the reverse of our mode;
that while man in breathing kept the oxygen and got
tid of the carbonic acid, plants in breathing kept the
carbonic acid and got rid of the oxygen.
108 The Ocean of Air.

Now, however, scientific :‘men do not usually regard
this operation as the breathing, but rather as the diges-
tion of a plant.

So if the leaves act the part of lungs, in exposing

to outside air the sap or blood of the plant, they also
act the part of a stomach in digesting the food obtained
from the air.

Plants, like animals, do breathe, and must breathe,
at least when actively living and growing, not only in
the day, but also at night. Plants, like animals, must
have oxygen. They, like ourselves, breathe in air,
keeping the oxygen and getting rid of the carbonic acid.

This goes on constantly. Digestion does not go on
constantly; it ceases at night; for leaves can only
‘ digest’ in sunlight.

So by the ‘ breathing’ of a plant is meant some-
thing analogous to the breathing of an animal. By
the ‘digestion’ of a plant is meant the peculiar work
done by green leaves, in breaking up carbonic acid gas
under sunlight, keeping one part, getting rid of the other.

It has been long known that plants send forth
oxygen by day and carbonic acid at night. If they
breathe like animals, they doubtless give forth carbonic
acid both night and day. That, however, which
escapes in the daytime is at once caught up again,
and digested as food, only the oxygen being freed. So
practically no carbonic acid is added to the atmosphere
by a plant in daylight. At night, when digestion stops,
it is able to escape. For this reason, plants in a bed-
room at night are not wholesome.

In any case, and whatever be the precise explana-
tion of these processes, there can be no doubt that the
great work of green leaves upon earth is that of Air
Purification.
How Plants Work. 10g

The work must of necessity be fitful and inter-
mittent in such a climate as ours. In the tropics the
luxuriant masses of vegetation carry it on with ceaseless
vigour, month after month, so long as the blazing sun is
above the horizon.

There is the real safeguard for the life of mankind in
the Ocean of Air. There is the mighty antidote to
carbon-burning, to animal-breathing, all over the
world. Thither relays of air are borne from north
and south in ceaseless streams for perpetual re-purifi-
cation.
PART III.

VAPOURS OF THE AIR-OCEAN,
CHAPTER XIII.
WATER IN THE ATMOSPHERE.

Arr is never perfectly dry.

We talk of ‘damp air,’ of ‘dry air,’ and of ‘ very
dry air’; but the dryness is at most only compara-
tive. Atmospheric air is not found utterly devoid of
moisture.

The use of the word ‘very’ shows this. If the

air were absolutely dry we should not call it ‘very’
dry. ‘square.’ . If something is spoken of as ‘ very square,’
we understand that the said thing is not usually square,
and that for once it nearly approaches to squareness.
So when we talk of the air as ‘ very dry,’ we only mean
that it approaches more nearly than usual to complete
dryness.
- The Ocean of Air which surrounds our earth is
commonly spoken of as ‘the Atmosphere.’ More
strictly it consists of two atmospheres, each separate
from the other. There is the atmosphere of dry air,
formed of oxygen and nitrogen mixed together ; there
is also the atmosphere of water-vapour.

The atmosphere of dry air remains always gaseous.
Except when locally interfered with for the moment by
burning and breathing operations, it also remains the
same in quantity and quality.
‘ 8
II4 The Ocean of Air.

The atmosphere of vapour is in a state of perpetual
change. The amount of vapour present in any one
place is always varying.

These two atmospheres float together, intermingled,
in the closest companionship. The particles of each
lie among and between the particles of the other.

This is a common state of things with gases,
because gas-particles are far apart. Two solids or
liquids cannot occupy the same spot; but two bodies
of gas or vapour do so without difficulty. Strictly
speaking, the loose floating particles of the one slip
freely in among the loose floating particles of the other.

As the atmosphere of dry gases is very much the
more abundant of the two, we usually speak of it
as The Atmosphere par excellence, and of the floating
moisture as an important and changeable ingredient
in the atmosphere.

Enormous quantities of watery vapour float at
all times in the Ocean of Air. For the air is inces-
santly at work, hiding away supplies of vapour in its
secret recesses, giving forth fresh supplies for the use
of the world.

You have watched the long cloud of white fog
pouring from the funnel of a steam-engine. Not smoke,
for smoke is unburnt carbon, and not steam, for real
steam is invisible, but white fog or mist springing from
steam. You have noted how quickly it vanishes.

That fog is made entirely of water. When it
disappears, the water has passed into the atmosphere,
there to float as invisible vapour.

You have observed a similar white fog pouring
from the spout of a kettle—more correctly, from the
stream of invisible steam which. issues from the spout
Water in the Atmosphere. II5

‘when the water boils. If you look closely, you will
notice a little space between the end of the spout and
the beginning of the small white cloud. The little space,
apparently empty, is filled with real invisible steam.

That cloud is all’ made of water, and it too
passes rapidly away as vapour into the air.

You have seen how a wet cloth hung before a fire,
or placed in warm sunshine, will gradually lose its
.dampness and become dry.

All the water which soaked that cloth, and made it
wet, has passed into the air, to float as water-vapour
in the atmosphere.

You have known ponds and rivulets shrink and
lessen, perhaps quite dry up, in a spell of hot weather.

The whole body of pond or rivulet water has been,
so to speak, drunk up by the thirsty air. No longer
visible as liquid water, it wanders free and unseen
:as vapour through the Ocean of Air.

This passing of water into the atmosphere is called
Evaporation.

Water, as already explained, may be at any time in
any one of the three forms of matter—the solid, the
liquid, and the gaseous.

It is solid as ice; it is liquid as water; it is gaseous
as steam or vapour. That which causes it to pass
from one state to another is increase or decrease of
heat.

The effect of heat upon almost all stfbstances is to
make them expand or grow larger. The effect of cold
‘is to make them contract or grow smaller.

Suppose you have an iron ball, which will just drop
through a ring, with no spare space left. If you heat
the ball it will grow larger, and will rest upon the ring,

8—2
4

116 ‘The Ocean sof Air

instead of falling through. .The heat has expanded
the substance, driving farther apart the minute separate.
particles of which it is made, so that as a whole it
must take up more room.

When a solid substance is melted or thawed into a
liquid, the liquid generally occupies more room than
the solid did. It has expanded or grown larger ; its
particles are farther apart.

There are a few apparent exceptions to this rule,
owing to the manner in which solids are formed
through crystallization. When water freezes into ice,
the minute ice-needles cross one another in a peculiar
method of arrangement, by which large unfilled gaps are:
left in the midst of them. Thus ice is really larger, and
occupies more space than the same quantity of water,
even though the tiny particles of each ice-needle have
actually drawn more closely together. The same thing
is seen with the solid and liquid forms of iron, of
bismuth, and of antimony.

Well for us that it is so with water! If water,
becoming a solid, shrank in size and increased in
weight, results would be disastrous. Every water
surface, in the winter of temperate regions, would
form, on the first frosty day, a layer of ice. The ice
would sink and remain at the bottom; another and
another ice-layer forming above, and sinking to bear
it company. In this manner every pond, every lake—
nay, even ocean-waters not far north—would become
dense masses of ice. No moderate summer-heat would
suffice to thaw these masses. That iron and bismuth
follow the same rule is interesting, but comparatively
unimportant to mankind. That water should do so
does appear to be a most merciful provision for the
world generally.

4
Water in the Atmosphere. II7

When a liquid substance is changed into-a gas or
vapour, the gas or vapour takes up always a great deal
more room than the liquid did. How much more de-.
pends on its degree of heat. In any case, it expands
enormously, the particles floating far apart.

This change of size or volume goes on to such an
extent, that one cubic inch of water will spread out into
nearly one cubic foot of steam.

A solid substance is of a certain definite shape, and
occupies a definite amount of room. The amount
varies slightly, since even a solid swells and shrinks a
little by being made hotter or colder. The gold ring
which just fits your finger on a cold day will probably
be rather tight on avery hot day; for your finger is apt
to swell with heat and to shrink with cold to a greater
degree than the gold of the ring. Still, the variation
with a solid is at its most slight. The shape, and
generally speaking the size, are constant ; if put into a
large empty box, it will not alter its shape, or grow
larger, to fill the box.

A liquid substance has no definite shape of its own,
but flows easily into the outlines of any vessel that may
contain it; while it too occupies a definite amount of
space. A pint of water, poured from a. pint measure
into a quart measure, will not swell out to fill the bigger
vessel. It will only spread to cover the bottom, re-
maining in quantity one pint still. Most liquids, like
solids, gently expand with heat and shrink with cold,
but to no great extent.

A gas or vapour has no particular shape, and
occupies no particular space. We may talk of ‘a
‘cubic foot cf steam,’ referring to the steam as it first
springs from boiling water, or to ‘a cubic foot of air’
at a certain distance above earth’s surface. In reality,
118 - The Ocean of Air.

the amount of steam or vapour, gas or air, which fills
a small vessel will also fill a large one. Gas is so
elastic as to be able to stretch itself to any extent.*

In the.matter of compressing gas into a smaller
space there are early limits; for a gas will by no
means endure any amount of squeezing. The separate
particles of a gas, more especially of a heated gas, are
always striving to get farther apart. To give them
extra room is to fall in with their ‘inborn’ tendencies ;
to press them closer together is to go in the teeth of
those natural tendencies.

Suppose you have a pint measure full of gas—of any
gas you choose, or if you like of common air—and a
quart measure emptied of air. You pour the contents
of the pint measure into the quart measure, taking care
to let none escape.

The pint of gas will at once expand to fill the quart
measure.

You then pour the contents of the quart measure
into a gallon measure, with the same precautions.t
The gas will instantly expand to fill the gallon measure.

In thus expanding, the gas or air grows thinner.
If you pull out a piece of elastic, it becomes thinner as
well as longer. The particles of gas move farther and
farther apart ; a less and less number of them are to
be found in each cubic inch of space.

But however large the containing vessel may be,
there is always as much gas in one part as in another
part. The gas is always equally distributed through
the whole. It always accommodates itself to the size

* The chief characteristic of a gas is said to be the power of
‘indefinite expansion.’

+ Of course such experiments as these can ouly be tried with
instruments made for the purpose. oe
Water in the Atmosphere. 11g

and shape of the vessel, stretching out in every direc-
tion, so as to pervade the entire space. It is more or
less dense according to the space it has to fill.

The density of the air in the lower levels of the Air-
Ocean is much affected by heat.

One cold morning, we will suppose, a man encloses
exactly one cubic foot of air, and weighs it. He weighs,
not the vessel containing the air, but the air itself,
just that amount of it which will fill, without stretch-
ing, a measure one foot high, one foot broad, one foot
deep. There are delicate instruments made for such
delicate weighing operations.

The weather changes, and becomes much warmer.
Some hours later the man does the same again. He
encloses another cubic foot of air, and weighs it.

He finds that the second supply, being warmer, is
lighter in weight than the first supply.

The reason why is not distant. Increased heat
has driven the particles of air farther apart. The
number of floating particles in a cubic foot of air is
not so great as a few hours earlier. Something more
than a cubic foot of air would now be required to weigh
the same as a cubic foot of air did in the early morn-
ing; for the material of which it is made is stretched
out more widely—therefore, it has grown thinner.

If we knew exactly how many air-particles were in
the cubic foot of cold air, and if we could now enclose
a supply of warm air containing just that number of
particles, it would weigh the same as the cubic foot of
cold air. But it would not be a cubic foot of air; it
would be larger.

Warm air near the level of the sea is always
lighter than cold air. Warm air swells, occupies more
120 The Ocean of Air,

room, and is disposed to flow upward ; cold air shrinks,
takes up less room, and is disposed to low downward.
This is equally true of the two interwoven atmospheres
—that of dry gases, and that of water-vapour.

In the higher levels of the Ocean of Air a somewhat
different state of things is found.

The density of the air is mainly the result of the
earth’s attraction, though also affected by heat and
cold. If it were not for the chaining power of gravita-
tion, each particle of air would rush as far as possible
from all other particles of air, till the entire atmosphere
had melted away into distant space.

This binding power steadily lessens, mile by mile,
with greater distance from earth’s surface, and the
weight of the down-pressing air above lessens also.

So in upper regions of the Atmosphere air expands,
not from heat, but from lessened weight and attraction.
The cold in those higher levels is intense; nevertheless,
the air-particles spring farther apart, and the air grows
thinner.

The atmosphere of vapour reaches to a great height,
but, like the atmosphere of dry gases, it is far less
dense above than below.
CHAPTER XIV.
ABOUT EVAPORATION.

Ir there were no water-vapour hidden away in the
secret recesses of the Ocean of Air, we should not only
have no dew, no clouds, no rain; we should not only
see all green things wither for lack of moisture ; but also
the sun would shine down upon us with a fierce and
glaring heat, such as now we can hardly even imagine.

The veil of floating moisture in the atmosphere acts
in two ways as a protection. It shelters us from excess
of heat and also from excess of cold. It keeps off some
of the sun’s burning glare from us, and also it keeps in
a great deal of the earth’s warmth for us.

As ascreen, it gently dims the glare, and steals some
of the heat from the travelling sunbeams. ‘The tiny
particles of invisible water help greatly to tone down
the fierce straight radiance of the king of day. - But
perhaps the work which is done by the vapour at
night is even more important.

All day long the ground gathers heat from the sun’s
rays as they beat downward, and when the sun dis-
appears the stored-up warmth begins at once to pour
itself out into space. If there were then no floating
vapour above to act as a sheltering screen, the ground
would lose its heat with very great speed, and the
suddenness of the chill would be fearful. The shield-
122 The Ocean of Air.

ing vapour prevents this, like a soft unseen blanket,
holding in earth’s warmth.

We all know how much warmer we feel on a cloudy
night than on a clear night. The clouds act as a
visible blanket or counterpane, radiating back to earth
its escaping heat. If there are no clouds the ground
loses warmth far more rapidly ; though even then there
is always the soft -fine veil of vapour—one of Earth’s
outer garments.

A man walking up a mountain or rising in a
balloon will find certain differences in the Ocean of
Air as he ascends, if he has with him the right instru-
ments for testing the state of the atmosphere.

He will find that the air has grown more thin or
rare; he will find that it has grown colder; he will
find that it has grown drier.

On the summits of great mountains the glare of
sunshine is often almost overpowering, even while the
frost is so intense that the sun’s rays are powerless to
melt the snow. One reason for the dazzling glare is
that the air contains there much less vapour than at
lower levels. The shielding screen of vapour has grown
thin and poor.

The floating vapour is not only more in amount
below than above ; it also varies exceedingly in different
places, and it keeps on varying.

Sometimes the air around us is damp, sometimes
dry ; sometimes it is wringing wet, sometimes parching.
These changes we know from our own sensations.

Everything wet or moist on earth gives off gentle
streams of vapour into the air, more or less abundant
streams according to its degree of warmth. Day and
night, summer and winter, the air is at work, receiving


Clouds over Loch Eitl, from the summit of Ben Nevis. From a photograph by Valentine & Sons.
About Evaporation. 123

or drinking up water from seas and rivers, ponds and
streams, clouds and fogs, earth and grass, plants and
animals; in short, from all damp surfaces of every
imaginable kind and description.

There are a few solid substances which steadily give
off of their material, somewhat after the fashion of
liquids. A lump of camphor, for instance, wastes
slowly away, growing smaller as its particles pass into
the air.

All liquids dry up, slowly or fast. If there were no
air they would still dry up at the same rate, or even
more rapidly. We may talk, and talk truly in a sense,
of the air taking in or drinking up moisture; but the
air does not cause evaporation. A damp surface
evaporates of itself, and the air receives the particles
of water as they leave the damp surface.

This is constantly going on. Where water is to be
found, there as a rule a soft vapour creeps gently away
into the atmosphere.

The same thing happens, though this is less
generally known, with water in the solid form. Both
ice and snow evaporate, creeping slowly away particle
by particle. Sometimes a whole slight fall of snow will
vanish thus, without any apparent thaw. More com-
monly, the fall is too heavy or the thaw comes too soon
for this gentle ‘ drying up’ to be noticed.

- So the air is ever at work, taking in moisture from
every possible quarter—until full !

Only until full! . Air will not hold unlimited supplies
of-hidden vapour. It will hold only a certain amount ;
just so much, and no more. Directly air is well soaked
—‘saturated’ is the right word—it refuses to take in
another particle. ‘Then evaporation grows languid, and,
perhaps, even ceases.
124. The Ocean of Air.

A laundress knows well, from sad experience, the,
difference between drying her clothes on a fine day and
on a wet day. She may be ignorant of the scientific
cause, but she is aware of the fact.

One week she hangs out her rows of wet garments,
and a soft dry wind sweeps past, stealing all the
moisture out of them with delightful rapidity. Another
week she leaves them to hang for hours, and the damp
motionless air has almost no effect—except, indeed, to
hinder evaporation. After hours of exposure, the
clothes are scarcely less wet than when first put out.
As she tersely expresses it, ‘They won’t dry!’ But
the garments are not wilful. The cause lies in the
overladen condition of the air, already so full of vapour
that it can receive no more.

A wind is always good for drying purposes. The
air around the wet clothes takes in some of the moisture,
becomes saturated, and declines any more. If no
breeze stirs, the soaked air remains hanging about the
clothes, and ‘drying’ is at a stand-still. But if a wind
blows, the wet air passes on, and fresh dry air comes
to carry off further supplies of vapour, and to be in
its turn speedily replaced. Thus the work proceeds
merrily. =

If you hold a sponge over a basin of water, letting
it touch the surface, the water will soak upward into
the sponge, till the latter is full and can hold no
more.

Just so with the atmosphere. It hangs like an
enormous sponge over all water-surfaces; and the
moisture soaks upward into the air till it is full.

There is, of course, a difference. A sponge draws
the water up into itself by means of what is called
capillary attraction. The air does not draw up vapour,
About Evaporation. 125

but merely receives the vapour which passes off from
water. Still there are points of resemblance. For
instance: the drier a sponge, the more water it can
hold; and the drier the air, the more rapid evaporation
is found to be. .

This drying process goes on over the whole world.
Even in the far north and the far south, where ice and
snow reign supreme, the samecontinues. Thesurfaces
of ice and snow are passing slowly away into the atmo-
sphere. In our temperate regions we are perpetually
aware of the fact of evaporation. More particularly it
is apparent in hot and dry summers. Then streams
vanish and rivers fall low, ponds disappear and springs
fail. But itis in more southern lands and seas that
evaporation is seen in full vigour.

The Mediterranean Sea is almost enclosed by land,
having only one narrow opening into the outside ocean,
through the Straits of Gibraltar. The whole of South
Europe and the whole of North Africa are drained into
the Mediterranean, countless streams and rivers pour-
ing thither by day and night their volumes of water,
gathered from surrounding tracts of country.

Under these circumstances, when we picture to our-
selves what is meant by such a watershed, we should
certainly expect to find a current flowing from the
Mediterranean into the outer ocean, through the Straits
of Gibraltar.

But no! The drying-up of the surface of the
Mediterranean is so enormous, that apparently it more
then balances the mighty influx of rivers from north
and south, east and west. powerful, current sets in from the Atlantic, through the
Straits, to keep the Mediterranean surface level with
the ocean outside.
126 The Ocean of Air.

Water always seeks persistently to maintain every-
where the same level. It can never rest for an instant
witha slanting surface. The smallest inequality means
an immediate flow of water from the higher to the
lower part; and the greater the inequality, the more
rapid will be the balancing rush.

So long as the Mediterranean is joined to the ocean,
though by only one inlet, its surface must be level with
that of the ocean. If its river and rain supply is greater
than its drying-up, a stream must pour out to the ocean.
If its drying-up is greater than its river and rain
supply, a stream must flow in from the ocean. If the
two are exactly equal, no stream need pass either
way.-

Since we find a stream setting in from the ocean,
we judge that more water dries up from the surface of
the Great Sea than is supplied by all the vast expanse of
land and rivers to north and south; not to speak of the
rainfall on the sea itself. There may be, however, a
further complication, in the shape of a probable under-
current flowing outward, as the upper-current flows in;
so we must not speak too positively.

Along the shores of India careful experiments have
been made to test the amount of evaporation. It is
found that about three-quarters of an inch in depth
daily passes upward from the whole sea surface. This,
if carried on equally all the year round, would give an
annual drying-up of over twenty-one feet in depth.
Even if, allowing for inequalities, we put the quantity
at fifteen or eighteen feet, it is startling enough.

Some mighty power must be at work to lift this
tremendous weight of water out of the ocean. When
one pictures what is meant by a mass of water fifteen
feet in depth and hundreds of miles in extent, one
About E vaporation. 127

gains some dim idea of the force which i is needed to
bring about such a result !

On earth no such force exists. If our earth stood
alone in the universe, this vast upheaving of ocean
waters into the atmosphere would not be accomplished.

When we see the steam which pours from a kettle
or a boiler changing fast into white mist, we know well
enough what force is at work. It is the Force of Heat.
The glowing fire has caused the water to boil, driving
it forth as steam into the air.

In the drying-up of waters upon earth, in the
evaporation of ocean surfaces, Heat is again the work-
ing power. The sun is the fire which supplies the
needed heat. The heat supplied by the sun enters
into the water, drives its particles farther apart, and
causes it to rise gently as invisible vapour into the air.

The heat which works on earth as fire all comes
from the sun. If no sun had ever shone in the heavens,
we could have on earth no burning coals, no flaming
gases,

In earlier chapters it has been explained how
combustion may be either a quick or a slow process;
quick, giving out much heat in a short time; slow,
giving out the same amount gradually in a longer
time. When combustion springs from earthly fire, de-
rived from the sun, it is generally more sharp and
quick. When the sun acts directly, the combustion is
more usually calm and slow.

The same difference is seen is the changing of
water into vapour.

It may be a quick ora slow process, giving out much
heat or little heat ina short time. If the transformation
is brought about by earthly heat, derived from the sun,
but acting by earthly methods, it is short and sharp,
128 The Ocean of Air.

much heat is given out, and the water rushes away in
scalding steam. But if the great sun himself does. the
work, acting directly on the water, he does it softly,
calmly, with no fuss or flutter; the transformation
takes place in silence, and the giving out of heat is
gentle because gradual.
CHAPTER XV.
ABOUT CONDENSATION.

Just as a sponge will hold a certain quantity of water
and no more, so the air will hold a certain quantity of
vapour and no more.

But the sponge will hold the same amount of water
at all times. The air will not hold the same amount
of vapour at all times. Whatever supply may be
hidden in the air at any particular moment, one never
can be sure how long that supply will be able to stay
there.

For the question, How much water can the air
contain? hinges on another question, How warm is
the air? Warm air can hold more vapour than cold
air. Hot air can hold more vapour than warm air.
The ‘carrying’ capacities of air for vapour depend
upon its warmth or coldness.

Happily, the very warmth which makes water to
evaporate more quickly also makes the air able to hold
a larger supply of vapour. So in the long-run, though
not instantly, a change of temperature tells in both
ways.

Suppose a layer ot cold air lies over a lake, receiving
more and more vapour until it is quite full. The drying
of the lake then grows very languid, from the fact of
the saturated air weighing down upon it and refusing

9
530 The Ocean of Air.

to take inany more vapour. Perhaps it may even stop
altogether.

If by any means you could suddenly make the cold
mass of air warmer it would be full no longer. It
would receive from the lake fresh vapour supplies until
again saturated. Another rise of temperature would
bring about the same result.

These variations of temperature do in fact happen
constantly from different causes.

Now let us view the question the other way.

A layer of warm air floats over a pond, and water
as vapour passes freely into the air till the latter is, in
childish parlance, ‘ as full as it will hold.’

Then a current of cold air from elsewhere comes
ereeping into the warm air, gaining some heat for itself,
and also cooling the warm air rapidly down, perhaps
two or three degrees.

What is to happen next? Cold air cannot possibly
hold so much vapour as warm air. The warm air,
having been saturated to its utmost extent, must, now
it has grown colder, be more than saturated.

If you have a large sponge full of water, ‘as full as
it will hold,’ and you give it a slight squeeze, what
happens?

You make the sponge smaller by your squeeze.
Consequently, it is unable to hold so much water.
Consequently, a few drops are pressed out.

Something analogous to this happens with the at-
mosphere. The current of cold air acts upon the
warm, as your hand acts upon the sponge, giving it
virtually a gentle squeeze. Thereupon some drops of
water are pressed out.

Occasionally, no doubt, the new current of air,
though cold, might be so dry as to have power to
A bout Condensation. I3I

drink in all the moisture which the other air could no
longer hold. Inthat case no change would be apparent.
Very often, however, the results of the squeeze are
plainly manifest.

Manifest, how?

As already said: by drops of water being squeezed
out.

The analogy of the sponge, however, fails us here,
for the drops from the sponge are large, and they fall
to the ground. The drops pressed out of the atmo-
sphere are extremely small and light, so much so, that
they float in the air ‘like very fine water-dust,’ as one
has said. All of them so floating in close company
make a mist or fog.

This is how the mist comes from the steam which
pours from the funnel of a steam-engine.

The heat of the engine-fires turns the water in the
boiler to steam. When the steam first rushes out into
the air it is invisible; but the air outside, already more
or less laden with vapour, cannot in one moment re-
ceive such a quantity of vapour. So a good deal of it
has to turn hastily to tiny floating drops of water,
streaming like a white cloud from the engine. As
fresh relays of unsoaked air come in contact with this
cloud of fog, the minute drops are sucked up, and soon
the whole vanishes.

Whether the mist vanishes slowly or fast depends
upon the kind of day. If the air is dry and thirsty,
the newly-made fog seems to melt away as if by magic.
But if the air is nearly saturated with damp, the tail
of fog from the engine hovers a long while in the air
before it can be hidden away.

On a dry day by the seaside, one may see the
funnels of distant steamers carrying a short banner of.

g—2
132° The Ocean of Air.

steam, which fast evaporates. On a damp day, long:
trails of white or gray fog from those same funnels will
lie far round the horizon.

We have already learnt that the passing of water
into vapour is called EVAPORATION. The passing of
vapour into water is called CONDENSATION.

These two, evaporation and condensation, are
exactly the opposite each of the other.

If a tumbler of water is emptied through drying
up, all the water passing into the air as vapour, that is
evaporation. If the escaping vapour were all caught
as it left the tumbler, were imprisoned, and through
the power of cold were restored as water to the
tumbler, that would be condensation.

Evaporation is caused by heat. The greater the
warmth of a liquid, the more quickly it evaporates.

Condensation is caused by cold. The greater the
cold of a vapour, the more quickly it condenses.

When water is evaporated, not one particle of that
water is destroyed. It has only changed into vapour,
vanishing from our sight.

When vapour is condensed, not one particle of
that vapour is destroyed. It has only changed into
water, returning to our sight.

No fairy tales or conjuring tricks were ever so truly
wonderful as this disappearing and reappearing of
water. We are all so used to the everyday marvels
of Nature that we forget to be surprised. Yet if this
were less common; if we had never known or heard
of the transformations of water until to-day; if we
suddenly were to see, for the first time, the whole circle
ot water-changes acted out; they would be to. us a
series of miracles.
About Condensation. 133

It was explained earlier how by the burning of a
candle, water is formed,—not liquid water but invisible
vapour, slipping away silently into the atmosphere.
Also it was explained that if a cold tumbler is held over
the flame, the glass is dimmed by a soft mist made of
tiny water-drops.

This is a case of condensation. The cold glass
acts like the cold breeze, cooling down the warm air,
and pressing out a little of its moisture.

On a frosty winter’s day, when we take a walk, a
tiny fog or cloud rushes from our lips with every
breath. Warm air, laden with moisture, ponrs from
the lungs. Meeting the cold air without, it is abruptly
chilled, and has to part with some of its vapour,
which changes into a mist of water-drops. The mist
floats for a second, till the dry surrounding air has had
time to drink it up.

Here, again, is condensation, followed by renewed

evaporation.
_ Ina railway-train compartment filled with people, if
both windows are shut, the glass will become thick with
haze. This haze is formed of water, and the colder
the outside air, the more rapidly it forms.

Within the compartment the air grows warm and
damp, through heat and moisture poured from several
throats. Being warm, it has no difficulty in carrying
the supply of vapour; but tke cold air outside chills
the windows, and the cold glass chills the layer of air
next to it. Then some of the vapour is pressed out by
the shrinking air, and is laid upon the panes as a collec-
tion of minute drops.

If this goes on, one layer of air after another
making its deposit—for where several people are
breathing and moving, the atmosphere cannot be at
134 The Ocean of Air.

rest—the tiny drops become presently so abundant as
to run one into another, joining to make big drops
which flow downward.

When the windows are thrown open, the moisture
on the panes soon vanishes. The outer air may be
cold, but unless extremely damp it will be able to
receive so small a quantity of additional vapour.

There once more is seen condensation, followed by
evaporation.

The two are perpetually at work on earth, alter-
nately and in opposition, neither knowing repose. The
amount of vapour in the air at any one place is always
changing, rarely for two minutes precisely the same,
unless we except the dead level of dryness attained to
by a tropical desert.

All over the whole earth water is vanishing and
reappearing; going out of sight into the air, and
coming into sight out of the air; being evaporated,
and being condensed; passing from the liquid to the
gaseous form, and from the gaseous to the liquid form.
Evaporation and condensation work in apparent oppo-
sition, yet each works into the other’s hands, so to
speak. Between the two is a perfect balance, which
results in order and beauty, circulation and life, upon
our globe.

When through condensation actual drops of water
appear, whether as mist or fog, dew or rain, the process
is also described as PRECIPITATION. The vapour-laden
air gives out, or drops, or precipitates, some of its surplus
moisture.
CHAPTER XVI.
DEW, MIST, AND FOG.

ON a fine autumn day the sun beats down for hours,
warming the Earth and the Atmosphere, and the warmed
air drinks steadily at every damp surface within reach,
till by evening it is well filled with moisture.

Then the sun sets, and there are no sheltering
clouds to hold in or reflect back the heat of the ground.
It pours out fast into space, despite all that the soft veil
of floating vapour in the air can do.

As the ground cools, it helps to cool the layer* of
air next above it. The touch of cold acts as a squeeze,
and immediately drops of water are pressed out,
minute floating drops, borne up by the air because
they are so small and light. Thus an evening mist is
formed.

Light as the floating drops of a mist are, it is ques-
tionable whether even they would be supported by
absolutely motionless air, since they are not actually
lighter than air. But motionless air is a thing almost

* When I speak of a ‘layer’ of air, I do not mean to imply
Separate layers in the atmosphere, like rows of bricks or sheets of
cardboard laid one over another. Air has no such divisions in its
make, but any substance may be pictured as divided into possible
sections ; and, in speaking of the air, it is convenient to imagine
Successive layers.
136 The Ocean of Air.

unknown. On the stillest day imaginable the air still
moves.

We often have such mists towards night, after
sundown, more especially when the ground is low
and damp, where therefore the air has been well
soaked. _

Mists and fogs are much alike, being both neither
more nor less than ground-clouds. ‘ A mist is com-
monly distinguished from a fog as being made of rather
larger drops, therefore feeling more wet.

Mists are often seen in the evening cr early morning
lying over rivers, sometimes most sharply divided in
their outlines, scarcely reaching beyond either bank,
but piled up within like a pack of cotton-wool. Water
will not part quickly with its heat like the solid ground,
and long after the earth and air have cooled down the
river-water keeps moderately warm.

Being warm, it continues to part with a good deal

_of vapour, more than the chilled air is able to take in.
So then a little bank of mist or fog is formed all along
the course of the stream, more or Jess dense according
to the warmth of the water and the coldness of the air.
The river keeps offering water to the air, and the air
keeps refusing to drink because it is not thirsty. Be-
tween the two, the rejected vapour turns into a cloud,
and hovers in a waiting attitude till air and water shall
come to a definite conclusion. This patience is generally
rewarded after sunrise by the warmed atmosphere
‘drinking up the fog with eagerness.

Sea-fogs are brought about in much the same
manner as meadow-mists.

The air which lies over the sea, having a free water-
surface to feed on, becomes filled with vapour. Then

‘a cold breeze from some new quarter blows into the


é.

FL M. Sutcli,

From a photograph by

Mist.
Dew, Mist and Fog. “137

-warm air, chilling it, and at once the hidden supply of
vapour becomes too great. A wet mist or fog is quickly
developed, thickening the atmosphere and blotting out
the horizon.

The perils of such a fog are sharply felt by those at
sea, and were sharply evidenced lately by a collision
between the Ostend and Dover mail-boats in mid
Channel. Suddenly and without warning, the passen-
gers of the lesser boat saw a great steamer burst
through the gloom close at hand, bearing down
upon them at full speed. There was no time to get
out of the way, no time to evade the peril, and the
worst that any man expected was not worse than the
reality. For the heavier vessel struck the other full
amidships, and cut clean through her as with a knife,
so that ‘the two halves of the stricken vessel fell away
from the bows of her assailant as a divided bank of
snow before the snow-plough.’ Strange to say, one of
the severed halves floated for hours after the collision.

Sea-fogs are often swept by a wind a short distance
inland, but over the dry ground they soon die away.

London fogs, too, spring into being after much the
same method. Two currents of air meet and mingle,
one warm and moist, the other cold. If the cold
current is dry enough to receive all the superfluous
moisture of the warm current, no marked effect is
seen. At the most only a slight haze is formed,
rapidly to be dissolved. But if, as is often the case,
the cold air already has its full complement of moisture,
then, when by contact it cools the warm damp air,
a fog must be the result.

The water of the Thames there is often warmer than
the air above it; and the same effect is produced as else-
-where by the sudden cooling of the ground after sunset.
138 The Ocean of Air.

In Town, however, an additional and very un-
pleasant element is found, from which country and
ocean are free. The air of London is always more or
less full of countless floating black specks, minute
portions of carbon, droppings from the smoke which
thousands of chimneys are ever pouring into the
atmosphere. Innumerable water-drops, squeezed out
of the cooling air, form around or cling to these tiny
specks, and they lend to the fog its peculiarly thick and
yellow or black look.

Once let a fresh breeze sweep over the City, bring-
ing fresh supplies of unsaturated air, able to hold more
moisture, and the fog quickly vanishes. It is sucked
up drop by drop into the interstices of the atmosphere.
But if no such breeze comes, and the air remains at
the same temperature, the fog may linger long, growing
probably worse and worse, as more smoke is weighed
‘down by the heavy damp air, to supply fresh carbon-
centres for new little drops.

Sometimes an unhappy variety for the Londoner
occurs in the shape of a fog overhead, not resting on
the ground, but most effectually cutting off the sun’s
rays. It is a little startling for a ‘country cousin,’
running up to Town for a few hours, out of a clear
atmosphere, to find the mighty City plunged at mid-day
into ‘ Egyptian darkness.’ This was my own experience
one April morning of the current year. To reach the
City. proved not difficult, though the outskirts looked
murky; but during a two hours’ business-interview the
air grew darker and yet more dark. Gas had to be re-
sorted to; and by one o’clock it was, to all intents ind
purposes, absolute midnight. No fog worth mentioning
was in the streets, and the lamps gave out their light
well ; but a dense pall overhead shut away all daylight.
Dew, Mist, and Fog. 139

It was as easy, no doubt, to go about as in any gas-
lighted winter night ; only it was not exactly what one
expected on an April day, and there was an unpleasant
consciousness that the overhanging pall of fog might
at any moment descend to the level of the pavement,
putting an end to traffic.
It seems not at all improbable that, even with
country and sea fogs, the floating drops of water always _
form around light specks of solid substance, borne up
in the air, too small and light to be perceived. Some
maintain that no fog, no mist, no cloud, can ever be
condensed out of the vapour in the air, without the help
of these minute particles for the water-drops to cling
to. If so, the floating dust of the air has a great
and important part to play in the vast water-circula-
tion of earth. It is only in large cities, however, that
these specks are so considerable in size and number,
as visibly to thicken the fog, and to endow it with
colour.

As London waxes yearly bigger, as chimneys grow
yearly more multitudinous, as fogs become yearly
more dense and overpowering, the future of the City
has a serious look. No doubt, however, when things
have reached such a pitch of misery that human
nature can endure it no longer, Englishmen will at
length put their heads together, and will devise some
method for burning instead of breathing their smoke.
One might well ask, Why wait so long? But the
average Londoner is a much-enduring individual,

There is another kind of evening condensation of
moisture often seen, and none the less singular because
common. This is the dropping of dew.

Dew-drops have something about them very pretty
I40 ~The Ocean of Air.

and poetical. They arrive so softly, without stir, not
pattering like rain, or clattering like hail, or accom-
panied by rough winds. Dew comes on warm and
still nights, creeping gently into existence, under cover
of the dusk, and fading quietly out of existence under
the early sunshine.

Dew does” not fall from clouds overhead; it is
commonly formed only when no clouds are there.
Clouds act as a blanket, holding in the warmth of the
earth, reflecting that warmth to the ground; and for
dew, the quick cooling of earth is needful. It comes
into being much after the same fashion as a meadow-
mist. Sometimes the two are found together, dew
dropping out of the lower layers of air close to the
ground, and mist being formed out of the next layers
of air above.

Properly speaking, dew is hardly ‘dropped,’ since
that would imply the falling of the drops, for at least a
little distance; and it appears that they do not fall.
The moisture is rather placed, or ‘deposited,’ by the
air, on any surface ready to receive it—much in the
same fashion that moisture is deposited upon the
window of a room or a railway-carriage, when the air
within is warmer than the air without.

The sun having set, the ground cools fast, if there
are no clouds; the air also, lying on the earth, is quickly
lowered in temperature. On astill evening, when it does
not move on, it reaches presently a stage called ‘ dew-
point.’ By this is meant that no dew has yet been
formed, but that the air can endure no further cooling, if
‘it is to hold still all the vapour it now contains. It is, in
fact, completely saturated. If the cooling continues, the
next step is the appearance of dew. Drops of water,
‘larger or smaller, are squeezed out of the air, and cling






FL Senn
= ip aes

open



Hoar Frost. From a photograph by F. M. Sutcliffe.
Dew, Mist, and Fog. 14

to grass-blades, leaves, twigs, spiders’ webs, and aught
else in their way.

The dew-drops are by no means equally distributed
over the ground. They favour most those substances
which part with heat most readily, which therefore
grow cold most quickly. Grass and plants lose heat
much faster than paving-stones or the road. So dew
is to be seen clothing grass and leaves with shining
drops, while pavement and road are still dry.

Sometimes the dew-point is down below the
freezing-point. Then the air, instead of depositing
drops of water, dresses fields and hedges, perhaps
even the whole landscape, in a coat of white hoar-
frost.

Hoar-frost isnot, as many suppose, dew first dropped
as water and then frozen. It is deposited at once in
the frozen and solid form. Like dew, it clings most
readily to those objects which part most quickly with
their warmth. Hoar-frost is often seen on lawn and
bushes, when the gravel-walk is free from it. Generally
the coating is slight, but sometimes it may be seen so
thick as to look like a fall of snow. On the shutters of
the Observatory at the top of the Puy de Déme it was
on one occasion actually three feet thick. °

In tropical countries, the amount of dew formed
is greater than anything we ever sec in temperate
climates. Travellers have found it possible, by pour-
ing the dew from one large leaf into another, to
obtain water enough for washing their hands. Much
of this abundant moisture sinks into the earth,
and feeds the thirsty roots of plants. When once
the tropical sun rises, all the dew which has not
soaked downward vanishes into the atmosphere like a
dream.
142 The Ocean of Air.

In certain American forests, dew is sometimes formed
at the level of the tree-tops. The abundance of it is
extraordinary, owing to the quantity of vapour in the
air and the rapid changes of temperature. It is said
that an actual shower of dew, like a shower of rain, is
occasionally felt below. This no doubt results from the
running together of the drops when formed, as moisture
deposited on a window will run together and flow
downward.

The slow heating and cooling of water has been al-
luded to in this chapter, and it will be repeatedly spoken
of again, in connection with winds, climate, and weather.
That peculiar characteristic of water, which is known
as its ‘great specific heat ’—in other words, the fact
that water requires more heat to raise it to a certain
temperature than perhaps any other known substance
—has widespread results. The touch of an Over-ruling
and All-wise Providence may be seen here. If water
could be warmed and cooled with the ease and rapidity
of other substances, the climates of many parts of Earth
would be in consequence so changed, that lands now
more or less densely inhabited would become almost
uninhabitable.
CHAPTER XVII.
THE MOUNTAINS OF CLOUDLAND.

WONDERFUL scenery is found in Cloudland by those
who love to study it—vast mountain masses and jagged
peaks, alternating with lakes and hills, dressed up in
glowing sunlight.

Yet the solidity of cloudland exists only in our
imagination. Clouds are, as a general rule, neither
more nor less than masses of wet mist or fog, floating
in the atmosphere, perpetually forming, diminishing,
vanishing, re-forming, growing, lessening again, never
remaining for any length of time in the same shape or
the same place.

Evaporation and condensation are unceasingly at
work in cloudland. Every mist-cloud that we look upon
is either growing or melting away. It is never a fixture.

True, some clouds seem to us to remain long in one
position, and to keep long one shape, if a few hours |
or less can be called ‘long.’ But in reality there is
not even that small amount of fixity. When they seem
to be at rest and changeless, it is only because they
are so far away that we cannot in a short space of
time detect the movements going on. Or else it is
because the whole sky overhead is shut off by a gray
pall of cloud, which may move or grow or lessen with-
out our being soon conscious of it.
144 The Occan of Air.

Like fog and mist upon earth’s surface, clouds are
commonly made and dispersed through the meeting of
two currents of air, one warmer than the other. If,
when the two currents mix, the air of the warmer is so
much cooled down that it cannot carry all its moisture,
while the air of the cooler is unable to take in more
moisture than it has already, then a new cloud is
formed ; or if a cloud is already there, it grows bigger.
But if, when the two currents mix, the air of the
colder gains so much warmth that it can receive more
vapour than it already has, then any cloud floating
there will be partly or wholly sucked up, so as to
lessen in size or to disappear.

This is the manner in which clouds often vanish.
Sometimes the wind carries them onward, out of our
sight. Quite as often they evaporate, or are dried up
by the air, vanishing exactly as the fog-cloud from the
funnel of a steam-engine vanishes.

On a tolerably fine day, when there is a fresh breeze,
and many small clouds lie rather low down, the changes
in the form and position of these clouds are astonish-
ingly rapid. Anyone may test the truth of this for
himself by watching with steady attention during
twenty or thirty minutes. But few people will take
so much trouble.

All clouds are not formed of mist or tiny water-
droplets. There is every reason to believe that some
are made of ice.

Clouds float at very different levels in the atmo-
sphere. Careful observations have been made in
several places, with varying results. When at a
great height it is believed they are formed, not of
fog or mist, but of tiny interlaced ice-needles. They
are, in short, frozen.
The Mountains of Cloudland. T45

Two facts bring us to this conclusion. One is, that
some curious effects, such as halos and mock-suns, are
occasionally seen through high-level clouds, and never
through low-level clouds. These effects are, in all
probability, caused by the refraction of light through
ice; since they could be thus produced, while they .
could not be produced by the passing of light through
mist.

The other fact is, that at so great a height the
cold is very intense, and water must almost of neces-
sity become ice. Ifa fog-cloud were there, it probably
could not remain a fog-cloud, but would have to
become an ice-cloud. On earth, at a certain tempera-
ture, we always have hoar-frost in place of dew, and
snow in place of rain. Just so in cloudland, at a
certain temperature, there would be frozen clouds in
place of mist-clouds.

Clouds, as already stated, commonly spring from
a cold current of air meeting a warm current. But
this is not the only mode in which they are formed.

A high mountain may often be seen capped by a
cloud of a certain well-defined shape, and this shape
will, perhaps, remain for hours, almost without change.
‘Sometimes, if the wind is high, a long slender ribbon
‘or tail of cloud will stream persistently from the top of
a lofty peak.

The warm wind of the lower country, carrying
plenty of moisture, suddenly reaches the mountain,
and has to rush upward. It cannot stop, for the
pressure of air behind forces it on. As it rises it grows
colder, and the chill of the ice-bound peak adds
further cold, compelling the air to part quickly with
‘some of the vapour so easily carried below. Thus a
cloud is formed.

zo
146 The Ocean of Air.

We may learn something more from this fog-
ribbon flowing from the peak, as to the nature of a
cloud. i

If you watch carefully the slender cloud from a
distance, you will find it keep the same shape for a
good while, unchanged; perhaps for hours. Then,
drawing nearer, you will find that, while the cloud
as a whole remains unaltered, the particles of which
that cloud:is made are never the same for two minutes
together.

The strong wind brings perpetually fresh supplies
of moisture-laden air, pouring up the mountain-side
from below, and the surplus moisture is perpetually
being condensed into fog by the cold peak. Yet the
cloud grows no larger. For the wind perpetually
carries away the fog to be evaporated anew into the
atmosphere. At one end of the long cloud-ribbon it is
born into existence out of the air, and at the other end,
indeed along its whole length, it dies out of existence
into the air. The cloud as a whole remains. But fast
as it is formed, so fast the air all around dries it up.
The water-particles of which it is composed are whirled
onward unceasingly, like the waters of a river.

The same thing, on a small scale, may be seen in the
little cloud which forms outside the spout of a boiling
kettle. The cloud keeps the same shape, remaining
intact, while the particles of which it is composed are
in ceaseless motion. Fresh particles rush momently
out of the spout to take their place in the cloud. Then
in their turn they are swept along and vanish from
sight.

This, in a greater or less degree, is the character of
all clouds—at least, of all lower-level mist-clouds. The
higher-level snow-clouds no doubt evaporate more


Clouds on the Himalayas. From a photograph by Shepherd & Bourne.
The Mountains of Cloudland. 147

slowly, just as ice and snow evaporate more slowly
than water.

Clouds are commonly divided into different classes,
reckoned according to their form and appearance, as
seen by us from the bottom of the Ocean of Air.

The three leading kinds are:

First—The Mare’s-tail Cloud, known as Cirrus.

Second—The Ground Fog, known as Stratus.

Third—The Woolpack Cloud, known as Cumulus.

But as we seldom find a perfectly pure specimen of
any simple substance, so we seldom come across per-
fectly pure specimens of these three simple types of
clouds. Far more commonly we see clouds which are
a mixture of two or three simple types, which therefore
we may call Compound Clouds.

The mare’s-tail cloud is usually regarded as a sign
of coming wind. Pure mare’s-tail, or cirrus, is feathery
and streaked, and lies always at a great height. A
balloon, floating over four miles high, seemed to
approach no nearer the distant cirri than when it
first left the ground. Clouds which are a mixture of
the mare’s-tail and ground-fog lie not quite so high,
though still at a level which probably means that they
are formed of ice, not of mist. It is through them that
‘mock suns’ are seen. Mackerel-sky clouds are a
mixture of the woolpack and the mare’s-tail. These
two lie lower than the pure mare’s-tail.

It is often difficult, looking up from the floor of the
Air-Ocean, to decide with any certainty which class
each particular cloud may belong to. Even practised
eyes are frequently at fault.

Ground fogs lie much lower in the atmosphere, and
much nearer to us, than those of the mare’s-tail type ;

10o-—2
148 The Ocean of Air.

therefore they have not such sharply-defined outlines,
but appear more hazy, more like masses of gray fog.
Because this kind is never found at any great height,
and because it often forms over low lands before night
to vanish in the morning, much like the evening mists
of marshy and damp places, it has been named ‘ the
ground fog.’ But it is distinctly a cloud far above our
heads, not to be confounded with mere fogs and mists
which rest upon the ground.

Sometimes the ground-fog clouds spread over iife
entire sky, shutting off aJl sunshine, while the air
below is foggy and dull. Commonly, however, they do
not mean rain.

Another kind of cloud which often overspreads the
whole sky, occasionally ushering in a storm, is a
mixture of the ground-fog and the woolpack.

The genuine rain-cloud, more or less a compound of
the three simple types, is simply that which the name
implies—the bringer, par excellence, of rain. Still, it
must not be supposed that every cloud which pours
drops upon earth is necessarily a ‘nimbus cloud.’

The woolpack cloud is usually formed of rounded
mountain-like masses, more or less white and woolly,
and often very beautiful in sunshine. It is com-
moner in summer than in winter. Piled-up heights
of snowy brightness, softened by gray shadows, are
visible against the blue sky on many a fine day. The
base of the mountainous pile is frequently a sharp
horizontal line, from which the fairy-like heights spring
upward.

This is the view which we have of woolpack clouds
lying at some distance from us, between the zenith and
the horizon. If such a cloud-mass is exactly overhead
we look up at a flat gray base which cuts off the sun-
The Mountains of Cloudland. 149

shine. There may be splendid piles of white cloud
above, but we can gain no glimpse of them. A man
who would see mountain peaks must be outside and
away from them, not under the mountain’s base.

Woolpack clouds are produced by a steady upward
current of warm air, carrying abundance of vapour.
As the air is cooled in its ascent, great quantities of
the vapour are fast condensed into masses of mist
or cloud, which collect into rounded shapes.

No doubt the most wonderful views of cloudland
are to be obtained from balloons. I cannot better
close this chapter or introduce the next than by
quoting from the vivid descriptions given by Mr.
Glaisher, of what he and his companions saw on two
occasions. The first extract relates to an ascent in
fine weather, the second to an ascent in wet weatlier.

“On the morning of August 21st, by half-past four,
my instruments were replaced, and we again left the
earth. The morning was warm but dull, the sky over-
cast with cirro-stratus cloud. The temperature was
nearly as high as 61°. ... We at first rose very
slowly. By 4.38 we were 1,000 feet high... . At 4.41
there was a break of clouds in the east, and a beautiful
line of light was seen, with gold and silver tints; we
were then still only at 1,000 feet. Here and there,
dotted over the land, the morning mist was sweeping.
At 4.51 the temperature was 50°. . . . Scud was below
us, and the night-cloud was in a transition state, forming
into the cumulus at the same level as we were, about
3,500 feet; black clouds were above, and mist was
creeping along the ground. ... At 4.57 we were in
cloud, surrounded on every side by white mist. The
temperatures of the air and dew-point were alike, as
both the dry and wet bulb read 39$°. The light rapidly
I50 The Ocean of Air.

increased, and gradually we emerged from the dense
cloud into a basin surrounded with immense mountains
of cloud rising far above us, and shortly afterward we
were looking into deep ravines, bounded with beautiful
curved lines. The sky immediately overhead was
blue, dotted with cirrus clouds. As we ascended, the
tops of the mountain-like clouds became silvery and
golden. At 5.1 we were level with them, and the sun
appeared flooding with golden light all the space we
could see for many degrees both right and left, tinting
with orange and silver all the remaining space around
us. It was a glorious sight indeed. At this time we
were about 8,000 feet high, and the temperature had
increased from 383° in the cloud to 41°. We still
ascended, rather more quickly as the sun’s rays fell
upon the balloon, each instant opening up to us ravines
of wonderful extent, and presenting to our view a
mighty sea of clouds. Here arose shining masses of
silvery heaps; there large masses of cloud in mountain
chains, rising perpendicularly from the plain, dark on
one side, silvery and bright on the other, with summits
of dazzling whiteness ; some there were of a pyramidal
form, and a large portion undulatory or wavy, in some
places subsiding into hollows, and in one place having
every appearance of a huge lake. Nor was the scene
wanting in light and shade. Each large mass of cloud
cast behind it its shadow, and this circumstance, added
to the very many tints, formed a scene at once most
beautiful and sublime.’

So much for cloudland in fair weather. Now for
the contrast, in a June ascent from Wolverton, with
concomitants of rain and high wind.

‘We were released by the simultaneous yielding of
the men, and in a minute were 4,000 feet above the




Cumulus Clouds. om a photograph.


The Mountains of Cloudland. I5r

earth. At this elevation we were chilled by the clouds
which we entered, but cheerfully looked forward to
emerging on the other side into the region of pure sky
and brilliant sunshine. On the contrary, all was gray,
colourless, and gloomy. At g,ooo feet the air was
filled with a moaning or sighing, like the wind previous
to astorm. This was our first experience of the sound,
and we listened to identify it with the cordage of our
machine working in the air; but it was the sound of
conflicting currents meeting and opposing each other
‘In the wilderness of space. Now we were two miles
high, with faint gleams of the sun, expecting him
momentarily to appear; instead, we entered a fog, and
then into a fine and wetting rain; afterwards a dry fog,
and then again a wet fog, and that was again repeated;
then we were mocked by gleams of sun, and found
that we had ascended three miles high. At 17,000 feet
there was no change. At four miles high, dense clouds
were still above us, and for a distance of two or three
thousand feet we were free from fog. To our surprise,
at this elevation, more than four miles above the earth,
there were dark masses of cloud, two layers one above
another, with fringed edges, unmistakable nimbi,
without doubt clouds of rain. At 23,000 feet, Mr.
Coxwell, who had been examining his ballast-bags,
decided that we must not only descend, but descend
at once. To my great regret I was therefore com-
pelled to content myself with a searching look of
general observation; but one momentary glance was
sufficient to impress it for ever on my mind, and were
I an artist, the impression was so vivid that I could
portray it in all its details. Above, below, all around,
the sky was nearly covered with dark clouds of stratus
character, with cirri above, and faint blue sky between;
152 The Ocean of Air.

not the blue of the morning, or of a dry atmosphere,
but as seen when the air is murky and the clouds con-
fused. The sense of storm and adverse weather
generally, which gave character to the scene, marked
it for ever as a memorable experience among many
others. As we passed down on our descent, at a height
of 14,000 feet we encountered a snowstorm extending
through nearly 5,000 feet. There were no flakes, only
spicule and hexagonal crystals, of distinct and well-
known forms. Below the snow, and almost 10,000.
feet from the earth, we entered again an opaque atmo-
sphere, which continued till we reached the ground.
This summer afternoon had exhibited many vicissitudes
of weather, and offered to the observer a fine and com-
prehensive study of meteorological influences at work,
removed from the immediate surface of the earth.’
CHAPTER XVIII.
RAIN, SNOW, AND HAIL.

THUS we see that a cloud, like a mist or fog, is pressed
by a cold air-current out of a warm one, to hang sus-
pended as a countless multitude of minute floating
water-drops.

Sometimes through a change of wind or tempera-
ture these drops are drawn anew into the air, and the
cloud vanishes.

But sometimes they go on increasing. More and
more vapour is turned into mist, and the cloud spreads
over a wider and wider extent.

Then the tiny drops get more and more crowded
together, till they begin to run into one another; and
so bigger drops are formed, which again join and make
still larger ones.

Now, though the air can hold up very tiny drops of
water, it cannot for any length of time support large
and heavy drops. Naturally, when they get beyond a
certain size they can be buoyed up no longer, but must
fall to the ground as a shower of rain.

It should, however, be understood that this ‘ certain
size’ is by no means always the same size. Moving air
can support a heavier weight than still air. A gale of
wind could keep floating above us drops which a gentle
breeze would have no power to hold up. This may
154 The Ocean of Air.

help to explain the difference in the sizes of rain-drops.
‘There are often strong winds blowing in the higher
regions of the Atmosphere when we have a calm below.

Sometimes the same thing is seen ina fog, which,
after all, is merely a cloud resting on the ground. The
tiny water-drops become so abundant that they run
together and form bigger drops, which fall to the ground
like rain.

But all this is a very partial explanation. There is
much that is mysterious in the formation of rain-drops,
and other forces, such as Electricity, have a hand in the
matter.

Rain, briefly, is caused by the chilling of air, which
contains a certain amount of moisture. This chilling
may take place either through the rising of air into
higher and colder levels; or through its contact with a
colder surface; or from its meeting with a colder current
of air. Rain often arises from the rushing of warm low-
land air up a mountain side; indeed, some of the heaviest
known rains are on mountains lying near the sea.

The air over the ocean gets thoroughly soaked with
vapour, which while warm it can well carry. Then
suddenly it comes against a mountain-range and has
to pour upward, losing heat as it does so. Becoming
fast colder, it can no longer contain its supplies of
hidden moisture. Then clouds of floating mist are.
formed, and torrents of rain are poured down.

Air, hurrying up a mountain-side, loses heat in two
ways.

The coldness of the mountain takes effect, chilling
down the warm air. Also, in rising to a higher level it
expands, becomes more thin, or ‘rare,’ spreading out
its particles over a larger space because of lessened
pressure. This expansion of air, or of any gas, always
Rain, Snow, and Hail. 155

mieans increase of coldness, heat being given out in the
act of expansion. Increase of coldness means lessened
power to carry moisture, which means nearer approach
to saturation, and therefore increased dampness.
Therefore, too, it means often heavy downfalls of rain.
So no wonder high mountains in hot countries are
often famous for the deluges with which they are
favoured.

The amount of rain which falls in different places
varies extremely. Taking all the year round, we havea
moderately abundant supply in the British Isles; but
nothing like what is known in tropical countries.

The fall of rain in London, except on rare occasions,
seldom exceeds an inch* in twenty-four hours; but in
other places this amount is enormously increased. At
Joyeuse, in France, thirty inches have been known to
come down in less than twenty-four hours.

If the whole amount which falls on the east coast of
England during a year could be carefully collected ona
level surface, no running away or sinking into the earth
or drying-up being allowed, we should have at the year’s
end a layer of water about twenty inches in depth. If
the same were done on the west coast of Ireland or
Scotland, the supply of water at the year’s end would
be six or eight feet deep. So even in the British Isles
there is a very marked diversity between different
places.

But if this same course were followed at a certain
hill-station in India, named Cherrapongee, a much

* Measured by means of a rain-gauge.

‘A gallon of water weighs ten pounds, and if spread out in a
layer one inch thick will only cover an area of two square feet. An
inch of rain gives 100 tons of water per acre, or 60,000 tons per
square mile.’— Scott.
156 The Ocean of Air.

greater result would be obtained, in the shape of a large
lake, at the very least between thirty and forty feet in
depth.

Cherrapongee enjoys the far from delightful emin-
ence of being one of the wettest spots on the face of
the earth.

Sometimes in cold weather we have snow instead
of rain.

Snow is not frozen rain. It falls directly as snow
from snow-clouds. In winter the frozen clouds lie at a
much lower level than in summer. Snow-clouds, like
mist-clouds, when they grow too heavy, have to part
with some of their substance, which falls to the earth
in white flakes instead of water-drops. Much more
than mere weight, however, is involved in a fall of
snow.

Snow-flakes are made of the most exquisite ice-
crystals. The minute needles group themselves into
beautiful star-like shapes, always six-pointed. Many
substances, when changed from a liquid into a solid,
will crystallize into delicate and beautiful forms, and it
is notably so with water. When, under free conditions,
water freezes into snow, the snow-crystals are always
formed of six-pointed stars or plates. That it is so we
can see with the microscope; but why it should be so
we do not know.

If very large flakes come down, they are caused by
the union of smaller flakes. The drier the air, the
smaller and harder will be, as a rule, the flakes; for
they cannot stick together unless a little damp.

Snow in England comes fitfully, and seldom lasts
long. Skaters have scarcely time to learn the use of
their skates before the opportunity is gone. Yet even


Snow on the Westmorland Mountains. From a photograph by Herbert Bell.
Rain, Snow, and Hail. I57

in England we have our exceptional winters of really
hard frosts and deep snows.

Towards the end of the seventeenth century, for
instance, the Thames was completely frozen over for
nearly three months, so that, according to an old
chronicler, ‘ it became a small city, with booths, coffee-
houses, taverns, glass-houses, printing, bull-baiting,
shops of all sorts, and whole streets, made on it.’ Food
was scarce, prices rose, and ‘the birds of the air died
numerously.’ Another such winter seems to have re-
curred about twenty-five years later, and again after an
interval of nearly fifty years, each differing from the
others in details, but all alike in severity.

In the present century the mightiest snow-storm yet
known was that of December, 1836. Many lives were
lost, and business generally came to a standstill for
nearly a week. The actual snowfall was said to be from
four to nine feet in depth, and snowdrifts were piled to
a height of twenty, thirty, forty, even fifty feet.

After all, the most excessive of English snowfalls are
but as child’s-play, seen side by side with that awful
visitation to which parts of America are subject—the
blizzard.

‘To constitute a true blizzard,’ writes Miss Gordon-
Cumming, ‘the whole atmosphere must be full of the
finest, most cutting ice-dust, sharp as powdered glass,
mingled with very small three-cornered frozen snow-
flakes, driven with appalling swiftness by a rushing
mighty wind, while a sudden fall of the temperature
from comparative warmth to thirty or forty degrees
below zero produces an intensity of cold which is
altogether unbearable, as we may well imagine who
deem ourselves frozen should the thermometer fall two
or three degrees below zero. . . . The blast sweeps on
158 The Ocean of Air.

with irresistible velocity, so densely charged with pul-
verized snow and ice, as fine as flour, that it obscures
the air with what is described as white darkness, ren-
dering large objects totally invisible at a distance of
two or three yards, and accompanied by such a roaring
and tumult that the human voice can scarcely make
itself heard within a few feet. The luckless traveller
who is caught in such a blast runs every risk of suffoca-
tion, the action of the lungs being stopped by the swift-
ness as well as the intense cold of the wind, while the
ice-dust—which penetrates the thickest clothing—is
more choking than the sand of the simoon....
Moreover, in the anguish of suffocation, the victims of
the blizzard seem occasionally to become insane before
dying, in some cases tearing off their clothes as if thus
to gain relief.’

One of the worst blizzards ever known raged
through several of the States on and after the rzth
of January, 1888, ‘an ice-laden hurricane’ awful in its
power. Within twenty-four hours the temperature
dropped from 74° above to 28° below zero, and in a
single hour blue sky was replaced by a wild storm
of powdered snow.

People were taken utterly unawares. Children died
by the roadside on their way home from school.
Farmers died in the fields before they could get to
their houses. A woman, stepping outside her front-
door to watch for her husband, perished there and
then, probably so numbed and bewildered as to have
neither power nor sense to turn back. Some even
under shelter succumbed to the overwhelming cold,
and were literally frozen to death; but the greater
number, at least of those exposed to the blast, seem to
have died of suffocation, fighting for breath, often
Rain, Snow, and Hail. 159

baring their throats in the terrible struggle for air.
Others, again, were found dead, stripped of their
clothes, which lay scattered piecemeal, as if flung away
one by one under the influence of madness. Such
dying madness in its victims is a well-known occasional
feature of the blizzard.

This great storm lasted unbroken for sixty hours—
three long days and nights of horror, of white dark-
ness, of a ceaseless hurricane-roar, of fearful cold, of a
stifling rush of ice and snow!

After such an account, one can hardly say much
about English winters !

Another form of frozen water descending from the
clouds is hail, and hail may fall in summer as well as
winter.

Hailstones are not made, like snow-flakes, of deli-
cate ice-needles, but neither are they shapeless lumps
of ice. If the formation of snowflakes is mysterious,
the make of hailstones is not less so. They too are
usually crystallized in beautiful shapes, though quite
differently from snowflakes. The manner of crystalli-
zation .is often so complicated, as to render it almost
impossible that they should have sprung into being
instantaneously, or as the hailstones fell from the
clouds.

Probably each hailstone begins with the freezing of
a drop of water, through a sudden rush of ice-cold air.
Round this central ice-particle other particles of ice
form in succession, taking curious shapes according to
certain laws of crystallization.

All this must occupy time; it could hardly be accom-
plished in a single second, possibly not in many
seconds. Yet how heavy growing hailstones, not
160 The Ocean of Air.

light and feathery like snow-flakes, but solid and firm,
can be borne up in the air while their formation goes
on is no easy problem.

In a. high wind, doubtless, they could be carried:
aloft much longer than in still weather; and hail is
usually accompanied by a gale. Moving air, as already
said in connection with raindrops, can bear a far heavier
weight than air in repose.

Still, there is much in the story of hailstones which
we are as yet unable to explain.

Hailstones as large as peas are common, and they
have been known to fall in Britain fully the size of
marbles. In the Orkneys they have been picked up
big enough to rival a goose’s egg; and even this
has been exceeded elsewhere, though many stories
of Brobdignagian hailstones may be dismissed as
mythical.

The true individual crystallized hailstone is never
very large. When great stones fall, they are merely
rough masses of small stones, glued together in the
course of their. descent by natural stickiness, probably
resulting from some degree of damp.

One of the heaviest falls of hail ever known in
England was during the thunderstorm of August gth,
1843. Itwas exceedingly violent in the neighbourhood
of Cambridge, and scarcely. less so in Oxfordshire.
An ‘extraordinary darkness of the atmosphere,’ with
clouds hanging so lowas almost to rest upon the house-
tops, dazzling flashes of lightning, and one long-.
continued unceasing roar of thunder, were enough in
themselves to be impressive; but to them was added a
deluge of hailstones, which lasted more than twenty .
minutes.

‘The scene,’ wrote Mr. Glaisher afterward, ‘ was


Stow.

Rev. F. W

by the

raph

Tcicles from a Waterfall, From a photogs
Rain, Snow, and Hail. r6r

positively terrific, and the fright of many of the
inhabitants of the town* was in no smali degree
increased by the crash of broken windows and the
inundation of their houses. During the whole of this
time, it was impossible for the eye to penetrate many
yards through the storm; the hail fell with such
wonderful closeness, and there was such a peculiar
mistiness rising from the earth, that a complete barrier
was opposed to the power of vision. We are almost
afraid to speak of the size of the hailstones, or rather
blocks of ice, but we are certainly not exaggerating in
the least degree when we say that very many of them
were as large as ordinary walnuts ; some, indeed, far ex-
ceeded this size: one that was picked up measured three
and a half inches in circumference, and several have been
described to us as being about as big as a pullet’s egg.’

Three hours after the storm was over, unmelted
hailstones lay in piles. One gentleman, finding his
horse unable to pull the carriage through them, stepped
out to clear a way, and sank up to his knees.

In Cambridge alone, where the brunt of the storm
fell, damage was done to at least the extent of £25,000.
Glass was shivered ; window-frames were dashed in;
fruit was ruineds birds were killed; crops were utterly
destroyed. In a single half-hour the standing corn
was stripped, laid flat, and literally cut up into little
pieces. Nothing of it remained for use! Well for us
that such outbursts are rare in England!

While on the subject of ice, a passing mention may
ve made of frozen waterfalls, often seen in other
countries, though not so common in England.

* Cambridge.
It
162 - The Ocean of Air.

The mere fact of a severe frost over the plains does
not ensure the freezing of waterfalls upon higher ground.
They usually occupy sheltered spots, where the radia-
tion of heat from the earth is less rapid than elsewhere;
and a slight or short frost has little power to chain the
falling water. But if the frost is severe and lasts long
enough, especially if it is accompanied by a dry and
bitter wind, the stream is at length more or less
mastered.

First the spray at the bottom hardens into a snow-
like mass; then the trickling water on either side
becomes solid. Each straggling drop is turned to ice
where it rests; and fantastic forms grow slowly into
shape, including hollow icicles, through which the ice-
cold water still flows.

Certain of the great Norway waterfalls gain such a
mass of frozen spray below, in the course of the winter,
that summer cannot entirely do away with it. Even
in England we see the power of frost to enchain a
falling stream. The Hardraw Force, in Wensleydale,
a waterfall one hundred feet high, built up in 1881 a
cone of ice at its base, no less than thirty feet high:
and a vast hollow icicle of more or less transparent ice
reached from the rock above to the apex of the cone.
Through this icicle or tube the stream poured down-
ward, clearly visible to one standing behind the fall, till
it vanished into the more opaque ice-cone below,
PART IV.
MOVEMENTS OF THE AIR-OCEAN.
CHAPTER XIX.
THE NATURE OF WIND.

THE Ocean of Air in which we live is never at rest.
Stagnation of our atmosphere is a thing unknown.

Streams of air-particles flow hither and thither,
forming winds from the north and east, winds from the
west and south, winds from every intervening point.
Some are variable hour by hour. Some are changeless
for months. Some are hundreds of miles in extent.
Some may be measured by yards.

. There are great rivers of air, as well as tiny brooks
of air, in the Air-Ocean ; just as there are vast streams
besides little currents in the water-ocean.

Our next step is to think about the various move-
ments of air, commonly called wind—those movements
which all together make up the world-wide Circulation
of the Atmosphere.

In some parts of the south and east of England
one may almost any day note the act of wind in turn-
ing the sails of a windmill. A pyramid-shaped tower
has a large light structure fastened to one side, formed
of four huge spreading arms or sails, each some thirty
or forty feet in length. Small crossbars partly fill up
the skeleton-shapes of these ‘sails,’ and more or less
of a canvas covering overspreads the crossbars. The
sails are set at such an angle or slope that when the
166 The Ocean of Air.

wind blows against them they move round under its
pressure, and thus work the grinding mill within. The
action of the wind upon a windmill sail is much, the
same as upon the sail of a boat—a kind of slanting
push, sending it onward.

Wind is nothing more nor less than Moving Air.

But why should air move? Why should not the
whole Ocean of Air remain at rest ?

We can picture to ourselves a great Ocean of Air
in perpetual sublime repose, a world without winds,
an atmosphere without circulation. Such a world with
such.a belt of air might not impossibly exist under
certain conditions; but it would have to be a very
different world from ours, a reposeful, not to say
stagnant, world, not spinning upon its axis day and
night. It would have to be a world without varieties
of heat and cold, of climate and weather. The moment
one part of the atmosphere is warmer than another part,
a disturbing element comes in, and the air begins to stir.

Wind commonly springs from what is called ‘ differ-
ence of pressure.’ If in one place the air is warm
and light, in another cold and heavy, the heavier air
must always flow towards the lighter air to keep up
the balance of the atmosphere. Just as water always
moves to preserve a level surface, so air always moves
to preserve an even balance.

Moreover, one current of air always causes other
currents. That is a fact worth remembering. Every-
thing that happens in Nature, as well as in our lives,
is always caused by other things going before, and
always helps to cause other things coming after. No
one thing in Nature or in Life stands alone, uncaused
and uncausing. ,

A current springs from different causes, but once
The Nature of Wind. 167

set going it is certain to cause other ‘currents. So
even if we had an ocean of stagnant air to start with,
it could not remain stagnant, so long as a single dis-
turbing element were there to upset its balance. Each
slight disturbance would draw countless other disturb-
ances in its train.

Moving bodies in the Air-Ocean are one source of
disturbance, and a very frequent source. We are not
commonly conscious of this. Nota handcan move, not
a sparrow can fly, without causing air-pressure and
consequent little air-breezes. But the fact does not
become apparent to us unless the moving body is
large, the compression of air tolerably great, and the
wind resulting somewhat strong.

We all know from experience what a wind is caused
- by the rush of an express train through a station, when
we are standing on the platform. Dust and sticks are
carried along by the whirl of moving air.

The same thing is seen on a much greater scale
with an avalanche.

Avalanches are of different kinds. Sometimes in
summer, on the higher mountains, they consist of
solid blocks of ice, dashing down steep slopes. In
spring they are more usually huge masses of soft co-
herent snow, gliding downward with frightful rapidity,
and overwhelming whole villages in the valleys below.

Another kind, quite as dangerous, is the drift
avalanche of winter. It consists of loose dry powdery
snow, first set going, perhaps, by a strong wind. In
the descent it gathers volume and speed, leaping from
precipice to precipice, till the tremendous compression
of air caused by its downward rush sets in motion a
far more violent gale than that which began its own
career. The mere wind from such an avalanche has
_ 168 The Ocean of Air. -

not only lifted a strong man bodily from a ledge and
borne him some distance, but has levelled trees and
shattered whole houses with its hurricane blast.

A mighty snow-mass will often break loose from
some frowning snow-ridge above, and will dash down-
ward, leaping from ridge to ridge of a great precipice.
At the first concussion the whole mass is broken
into fragments, and soon only a cloud of white dust
is seen to flash like lightning from point to point, roar
following roar, till the last leap is taken. Woe betide
anyone so unfortunate as to stand in the path of
such an avalanche, or within reach of its rushing
wind!

But to come back to a very everyday matter:
what is it that causes an ordinary draught in a room
or public building ?

The draughts in St. Paul’s Cathedral are pretty
well known to Londoners. If no disturbing elements.
existed, the mass of air within our great cathedral
might remain calm and moveless; but this is a state
of things seldom if ever possible, certainly never
possible when a crowd of human beings is gathered
under the dome. The heat given out by their bodies,
and the hot air pouring from their lungs, warms the
atmosphere in and near the centre. Then the warmed
air rises, and streams of cold air pour centrewards
from the side aisles to supply the place of that which
passes upwards. Thus a draught is created, and old
ladies draw their shawls tightly round them, and old —
gentlemen cast savage looks at the vergers ; but neither
old ladies nor old gentlemen blame themselves as being
in part the physical cause.

It often happens that on the sea-coast, especially in


Wind-blown Trees. From a photograph by F. M. Sutcliffe.
The Nature of Wind. 169

hot countries, land and sea breezes regularly alter-
nate.

All day long a fresh breeze from the sea will blow
in upon the land. In the evening that will stop, and
after a pause a land-breeze will for hours blow steadily
out to sea. In the morning another pause is followed
again by the sea-breeze.

The direct cause of these breezes is the rapid
heating and cooling of the ground. Land grows warm
much faster than water, and also loses its warmth
much faster. Water heats slowly, and, once heated, it
cools slowly.

All day the ground becomes warmer and warmer
under the burning sun, and helps to heat the layers of
air above. The cooler and heavier sea-air has to flow
in upon the warm and light land-air.

After sundown the reverse happens. The ground
cools fast, helping to cool the air above, while the sea
keeps warm. The air over the land, becoming the
coldest and heaviest, has to flow towards the more
warm and light air over the water.

Some explain this by saying that the cold air flows
towards the warm air, because the latter, being light,
has a tendency to rise, and to leave a space which must
be filled.

Another explanation is as follows: The warm air is
enlarged by heat, and expands or swells upward, rising
‘like a blister’ on the outer surface of the Air-Ocean.
The upper layers of air, being piled too high, have to
slide away to a lower level over the colder air. Then
the added weight and pressure over this colder. region
forces the air below to flow towards the region of warm
and light air. It is, in fact, readjustment of the
balance.
170 ~The Ocean of Air.

All around the earth, near the equator, are hot
countries, lands where the sun beats fiercely down,
warming soil, sea, and atmosphere. This causes on a
large scale what has just been described on a small scale.

The air, being peculiarly laden with moisture in
those regions, is peculiarly susceptible to the heat of
the sun. Vast masses of air, already warm, are more
and more heated by the sun’s rays and by the burning
earth below, till they are far lighter and ‘larger’ than
air elsewhere. Then the cooler heavier smaller air
comes pouring in from north and south to restore the
‘balance’ of the atmosphere.

I use the words ‘larger’ and ‘smaller’ with
purpose; for literally the air of lower levels does
expand or grow bigger with heat, and does shrink or
grow smaller with cold. A mass of heated air weigh-
ing one pound is as truly larger than a mass of cold air
weighing one pound, as one pound of heated iron is
bigger than one pound of cold iron.

The air in the tropics near the equator grows hot,
expands, gets large and light. This means that the mass
of the atmosphere thereabouts occupies more space than’
if cold, its particles being more widely separated.

The result, if we could see it, is doubtless an actual
swelling upward of the outer surface of the Air Ocean—
the rising of a huge blister or air wave, pushed outward
by the enlarging of the air below. Nowthe Air-Ocean,
like the water-ocean, flows hither and thither in a
perpetual struggle to keep itself even. Like the water-
ocean it may surge out at its upper surface* in great

* The word ‘surface’ is of course used with a reservation. The
atmosphere probably thins away so gradually that no man, if able
to examine for himself, would be able to say where it ceased. But

since the Air-Ocean does not extend through space, it must te
somewhere.
The Nature of Wind. I7I

waves, but those waves are sure to fall back and flatten
themselves out. The superfluous air, piling itself
above, has to flow away in mightv currents towards
the north and south.

As these streams pour off, they cause extra weight
and pressure where they go; and other currents pour
in below, just as we saw was the case in St. Paul’s
Cathedral.

We may be quite sure of one thing in the matter of
Air Circulation. Whatever quantity of air flows towards
one particular place, the same quantity of air must flow
away from that place. Also, whatever quantity of air
flows away from one particular place, the same quantity
of air must flow towards that place. No part of earth
can be left with less air or more air than any other
part. Soa perpetual struggle to make things equal is
carried on over the whole world; air rushing hither
and thither in streams to restore the balance, which,
as soon as it is restored, is directly upset anew.

All round the earth, to the north of the equator,
except where disturbed by other influences, lies a broad
belt of winds, always blowing towards the equator
from the north-east, known as the Trade-Winds. The
belt reaches from near the equator to about 30° north
latitude; and the streams of air continue day and
night, night and day, with more or less intensity,
throughout the year. Exactly the same kind of trade-
wind belt is found also to the south of the equator,
only as these winds too blow towards the equator,
they come from the south-east.

The northern belt is known as the zone of the
North-East Trades, and the southern belt as the zone
of the South-East Trades.
172 ~The Ocean of Air.

In bygcne years the trades were a great perplexity
to sailors—and often a serious difficulty. It was all
very well so long as a ship wanted to sail in the direc-
tion whither the trade blew. The mariner might lash
his helm, and go to sleep if he chose, leaving the look-
out to a girl or a child, for a long run through the open.
sea. He could be absolutely secure of a good fresh
breeze, always from the same: point, never ceasing and,
never growing too strong. But if he wished to sail
in the teeth of the trade, that was another matter.
Wishing for a change of wind was useless work, for the
wind never did change. -

Now that men understand the extent and limits of
the trades, knowing where they are constant, where
they change with the season, and where land influences
check or draw them aside, the sailor can make use of
or avoid the trades as he will.. Moreover, the wide-
spread use of steam makes the direction of winds a
less vitally important matter than of old, in a large pro-
portion of cases.
CHAPTER XxX.
THE CIRCULATION OF AIR.

ALL round the world on and near the equator lies a re-
markable band of calm air. Thenorthern trades meet
there the southern trades, and each tends to counteract
the other.

This Belt of Calms, known as the Doldrums, has
to be passed by every ship going from one hemisphere
tothe other. Sailing vessels have often been kept there
for weeks, unable to advance, like that of the ‘ Ancient
Mariner ’—‘ as idle as a painted ship upon a painted
ocean.’ In olden days, before steam power was known,
passengers to Australia or South America were often
long delayed.

Though wind is scant, rain is abundant, sometimes
to a tremendous extent. Old sailors tell of such
deluges, combined with dead calms, that fresh water
has absolutely been ladled up from the surface of the
still ocean.

The trade-wind belts have been already described
as currents of air pouring constantly from north and
south towards the equator. These are on the surface
of earth, low down in the Ocean of Air. High up in
the atmosphere, above the trades, are two exactly
opposite currents of air, known as ‘ anti-trades,’ pour-
ing away from the equator towards the north and
174 The Ocean of Air.

south. They too have been mentioned earlier, as the
result of the heated air over the equator.

As there are upper and under currents of water in
the ocean, so there are upper and under currents of air
in the atmosphere. The wind may blow where we
stand straight from the north, but that is no proof that
higher up the wind does not -blow direct from the
south. Careful watching of clouds shows often that
the upper layers are travelling in a perfectly different
direction from the lower layers.

‘Before a thunderstorm, when attention is drawn to
the sky, we often hear it remarked that ‘ the cloud has
come up against the wind.’ The cloud has, of course,
done nothing of the kind. A cloud can no more float
in the air against the wind, than a log of wood can float
in a river against the stream. The cloud is merely
borne towards us by a different current of air from that
which at the moment we feel. The same fact of
differing air-currents, though less sharply marked than
in stormy weather, may be seen on many a fine and
breezy day; but people do not commonly observe.

The anti-trades lie very high up, so high that no
mountain-climber has walked out of the lower trades
into the anti-trades.. Towards the outer verge of the
trade-belt, however, the anti-trades are found descend-
ing to lower levels, and even without this there are
abundant* proofs of their existence.

* We know from the sheer exercise of common-sense that all the
piled-up air over the equator must go somewhere ; that as streams
of air are always pouring towards the equator, counter-streams
must flow away.’ Also, clouds at a great height have been seen
travelling, or rather seeming to travel, in the very teeth of the trade
below, while volcanic ashes have been carried for days in a direction
just contrary to the trade, borne over the top of it, in fact, before
being dropped to earth.
The Circulation of Air. 175

‘Beyond the trade-belts, to north and south, lie two
more so-called ‘calm belts.’ That to the south is
named sometimes: ‘the Calms of Capricorn,’ that to
the north ‘the Calms of Cancer.’ Some know the
latter as ‘the Horse- Latitudes.’ A very obvious
connection exists between ‘ sea-horses,’ ‘ mares’ tails,’
and high winds, which is rather at variance with one’s
notions of calmness. The Cancer Calms are, however,
of a most variable nature, much broken by severe
gales and heavy storms.

There is a marked difference between the calm-
belt of the equator and the two calm-belts of the
tropics. .

The calm-belt of the equator has incessant currents
of air pouring in below from north and south, while
incessant currents of air flow away above. So the
tendency of the air there must be to rise steadily
upward.

In the so-called ‘calms’ of Cancer and Capricorn
—regions really of unsettled winds and violent storms,
‘alternating with wearisome calms’ *—things are just
the other way. .Streams of air pour in above from
north and south, while streams below flow out towards
north and south. So the tendency of the air there
must be to sink steadily downward, causing pressure
from above,—which indeed has been noted as markedly
shown by the barometer.

There is also a considerable difference in the con-
dition of air-currents flowing from the equator to
north and south, and air-currents flowing from north
or south to the equator. The equator is the largest
circle of latitude, and all other such circles, from the

* Scott.
176 The Ocean of Air.

equator to the poles, grow smaller and smaller. If a
current of air pours from the north pole to the equator;
it runs in an ever-widening bed.. This may be seen by
following the course of two longitude lines on the globe,
beginning at the pole and ending at the equator. But
an air-current travelling the other way moves in an
.ever-narrowing bed. In the first case it can spread
itself out ;. in the second it has less and less room.

Regions north of the Cancer Calm and south of the
Capricorn Calm are no longer characterized by such
persistent winds as the trades and anti-trades. Still,
the great Circulation of the Atmosphere goes on, only
in a more irregular mode; and even there something
of a rough ‘plan’ may still be detected.

The winds of the region between the ‘ horse-lati-
tudes’ and the north pole may seem to wander here
and there, without aim or rule; yet on the whole there
is a general tendency of air-currents below to flow
towards the pole, and of air-currents above to flow
away from the pole.

In the northern hemisphere these winds have little
fair play, being constantly interfered with by the rapid
heating and cooling of great continents. But in the
southern hemisphere, where much. ocean and little
land are found, westerly winds, circling around and
towards the south pole, have full swing. Not only are
they almost as persistent as the trades, but far stronger,
becoming at times so violent as to have gained for that
region the expressive cognomen of ‘the Roaring
Forties.’

These winds are westerly, not, as one might expect,
southerly.and northerly. They do not travel. towards
the poles from due south and.due north, but rather
more a westerly direction.
The Circulation of Air. 177

One reason for thisis not hard to find. If the whole
surrounding atmosphere poured straight in upon either
pole, the piling up of air above the poles would be tremen-
dous. A general influx of air from all sides could scarcely
be balanced by any amount of flowing away above.

Such a state of things is not possible. The winds
nearing the poles must with lessening space play
round and about, must approach rather by circling than
by direct lines, each air-current fitting in as it can with
other currents.

Another reason for these ‘ westering’ gales of low
latitudes, is connected with the daily whirl of our earth
upon her axis.

In an earlier chapter we saw how the atmosphere
revolves with the earth, from west to east, each part of
it at the same speed as the ground on which it rests.
We saw how the air at the equator has a steady speed
of one thousand miles or so an hour; while at the poles
it scarcely moves at all; and all the way between the
poles and the equator it moves, like the ground, at
different rates.

Now, when air comes from the north towards the
equator, it partakes of the slow northern whirl; and as
the earth below rushes faster and faster, it lags behind,
seeming to come, not from the north, but from the
north-east. When, on the contrary, air flows from the
equator towards the north, it partakes of the rapid
tropical whirl; and as the ground beneath moves more
and more slowly, it out-races the earth, appearing to
come, not from the south, but from the south-west.
Thus the trades blowing equator-wards, which would
be northerly winds, become north-easterly ; and those
winds blowing pole-wards, which would be southerly,
‘become westerly.

12
178 The Ocean of Air.

We have now some idea of what may be called the
‘rough draft’ or general outline of Atmospheric Circu-
lation. Briefly, it is as follows:

1. A belt of calms, on and near the equator; winds
flowing in below and flowing out above.

11. On either side a belt of steady winds—the
trades below, flowing towards the equator; the anti-
trades above, flowing away from the equator.

mI. Outside the trade-belts ; to the north a belt of
Cancer calms; to the south a belt of Capricorn calms;
the winds in both cases flowing in above from north
and south, flowing out below towards north and south.

Iv. Beyond the calms of Cancer to the north, and
beyond the calms of Capricorn to the south, a belt
of variable winds; below, more or less westerly and
tending towards the pole; above, tending away from
the pole.

v. At the North Pole and at the South Pole a
region of comparative calm; winds mainly flowing in
below and flowing out above.

Thus acontinuous Circulation of Air is kept up over
the whole earth. No part of the atmosphere is ever at
rest ; but a perpetual interchange of air-currents goes
on everywhere.

One may, in imagination, follow the progress of an
air-particle, starting from the equator, and performing
‘the grand tour.’

At the equator it rises upward into higher regions ot
the atmosphere. As part of an anti-trade it journeys
northward, passing over the contrary-blowing trade
below. In the Calms of Cancer it descends to earth,
plays about in a storm or two, and takes its choice
between joining the stream of air which at once returns
The Circulation of Air. 179

to the equator, and joining the stream of air which
more fitfully finds its way towards the North Pole.
Having been carried away by the latter, this wandering
particle is borne to and fro by many breezes, visiting
divers countries, yet on the whole progressing north-
‘ward.

Reaching at length the neighbourhood of the Pole,
the particle finds itself in another region of comparative
calm, though by no means a region where storms are
unknown. Rising upward after awhile, it joins a
high-level current of air proceeding southward—an
infant trade-wind in fact, though hardly yet to be
recognised as such. Gaining once more the Calms of
‘Cancer, it descends anew, and this time passes out
‘below to the southward, as a part of the north-east trade.

At the equator, again, the particle works its way
upward as before, and joins the upper current, flowing
southward as part of an anti-trade. Reaching the
‘Calms of Capricorn it descends, passes thence below,
through the ‘roaring forties’ towards the South Polar
‘Calm, finds an upward path there to the out-flowing
currents above, returns to Capricorn, descends afresh,
joins the south-east trade, .and reaches the equator
ready to begin the round anew.

This circle of possible movements for a single air-
particle might be almost infinitely varied by permitting
it to join any of the innumerable side-currents and
‘eddies of air caused by countless land influences. It
‘should become part of a monsoon here, part of a hurri-
‘cane there. It should unite itself to a cyclone in one
place, to an anti-cyclone in another. Though the
broad outlines of Atmospheric Circulation may be
sketched with a certain regularity, the variations upon
that rough plan are past counting.

I2—2
180 The Ocean of Air.

In the Air-Circulation of earth, as in the Blood-

Circulation of a man’s body, there are little arteries as

-well as great arteries, and hundreds of tiny streams for
every big stream.

‘The wind goeth toward the south, and turneth
about unto the north; it whirleth about continually,
and the wind returneth again according to his:
circuits.’

What'I have tried .o explain in many paragraphs
is given thus in five-and-twenty words of Holy Writ—
the Circulation of Air described in a nutshell !
CHAPTER XXI.
MORE ABOUT THE WILD WINDS.

IN the Circulation sketch of the last chapter, showing
how the ‘ Air of the Atmosphere’ flows ceaselessly to
,and fro over the whole face of the earth, the two halves
‘of the earth were coupled together.

Not wrongly so, for the bare outline of the general
plan is the same both to north and south of the
equator.

Still, the one half of the world is very far from
-being an exact copy of the other half. Exact copies
are common enough in human works, but not at all
common in Divine Handiwork. There we have infinite
variety filling up systematic outlines. Since no two
leaves of a tree have ever been found absolutely the
same in form, it is, to say the least, improbable that
one half of a world should be a slavish imitation of the
other half.

If the entire earth were covered by one enormous
ocean of water, then indeed such a system of winds
might be carried out in all its parts, with little or no
variation. The Circulation of the Atmosphere would
be in that case less difficult to ‘understand, and less in-
teresting to study, than it is now.

But our world contains much land as well as much
sea, and where land exists the rapid heating and
182 The Ocean of Air.

cooling of it cause great varieties of air-currents,
breaking through ‘ general plans’ to any extent.

Broad belts of trade-winds have been described,
enfolding the earth like sashes. These trade-winds
do exist, and they would exist all round the world
throughout the whole year, if not hindered. But in
places they are very much hindered.

Suppose, for instance, a burning desert not far from
a trade-wind region. The air above the desert becomes
in the summer months tremendously heated, swelling
in size, and flowing upward. Then arises a need for
heavier air to flow from somewhere else towards the
desert, to restore the lost balance of the atmo-
sphere.

The trade-wind lies conveniently near; and it is of
no use to protest that the said trade is wanted near
the equator. Here is the most pressing need for the
moment, so the busy trade is bent out of its regular
course to become a sea-breeze blowing inland, and the
needs of the equator have to be supplied from some
other quarter.

Such needs always are supplied. The balance of
the air must be kept. If the steady ordinary winds
are not equal to their task, a hurricane or two will
intervene, doing in a very short time the work
required.

Land-influences of this kind so often divert the
trades, that they can only be said to hold full sway
over the broad reaches of ocean, not usually upon
continents.

Monsoons are in general merely turned or ‘deflected’
trades, drawn by over-heated land from their proper
route. The ‘Indian monsoon’ is a familiar phrase to
most English people, at least to those who have rela-
More. about the Wild Winds. 183

tives in India. It is commonly applied to-the ‘soft
south-west monsoon,’* which brings the rainy season.

Here is a little description of the ‘rainy season,’
written by onef on the spot, which helps to bring it
before our imagination:

‘IT wish you could see how it.rains. For eleven
whole days it has come down incessantly, and the
compound is like a lake. People are beginning to
grumble, but I like it. The air is so much fresher and
pleasanter, and one feels so much more alive, than in
the terrible heat which preceded this downpour.’

And again in August, nearly two months later :

‘ The rain is most persevering. It comes down, not
in ordinary drops, but in sheets of water. The whole
place is ankle-deep, and I have just been watching the
servants wading through the slush with queer little
wooden umbrellas over their heads, bringing in the
dishes for breakfast. All Indian kitchens, you know,
are at a little distance from the house. Everything is
damp and disagreeable and mouldy. It is quite an
occupation to look after one’s books and clothes, and,
after all, no careavailstosavethem. The books would
break your heart; their faces, so fresh and fair when we
left home, are spotted and spoiled. The very pillows
smell as if they had come out of a charnel-house; the
gloves you wear to-day are white with mould to-morrow;
your boots the same; and your very hair seems mil-

* Two monsoons blow regularly in India, taking turns. The
south-west monsoon lasts about five months, from May to October;
the north-east about another five months, between October and
May, each being divided from the other by an irregular month,
called ‘the breaking of the monsoon,’ during which violent storms,
and even hurricanes, often take place, in the struggle of the dis-
turbed atmosphere to regain its lost balance.

+ Mrs. Murray Mitchell's ‘In India’
184 The Ocean of Air.

dewed. .. . Nature just now is wildly luxuriant and
beautiful—the effect, of course, of the bountiful monsoon.
The woods are full of rich loveliness... . The very
ditches are turned into beds of beauty, covered thick
with the beautiful caladium leaves, blotched and
streaked with crimson and purple and brown.’

Now, the south-west monsoon is nothing more nor
less than the north-east trade of that region completely
turned or doubled back upon itself and made to flow in
steady currents over India. But what of the north-east
monsoon, which flows during the winter months of the
north?

Why, that is only our old friend, the north-east
trade, unchanged. When the influence of the deserts
lessens through cooler weather, the trade returns to its
natural course, and flows once more towards the
equator.*

Perhaps the force of moving airis shown in no more
marked way than in its lashing of the ocean surface
into mighty waves.

Even when standing on the shore one may gain
some idea of the tremendous power of ocean waves,
lifted and driven onward entirely by the pressure of the
gentle transparent air, which floats so sleepily round us
on a quiet summer’s day. Without an Ocean of Air,
the ocean of water would be waveless.

As good a view as any of ocean-billows, seen from
the safe vantage of firm ground, may be obtained on the
Chesil Beach, a long reach of shingle, extending be-
tween Portland and the mainland, ten miles and more

* The world has other monsoons beside those of India. There
are the African monsoons, caused by the great African deserts
drawing aside part of the Atlantic trade ; and there are the Central
American monsoons, formed out of deflected Pacific trades.


Breakers at Bognor. From a photograph by W. P. Marsh.
More about the Wild Winds. 185

in length, and rising to a piled-up shingle-height of
about sixty feet. If a strong wind blows from the
Atlantic straight upon the ridge, a curious contrast can
be seen by one standing on the summit.

Within, the bay between Weymouth and Portland
lies calm and blue, still as a lake, broken only by ripples.
Without, beyond Chesil Beach, a boiling sea of great
waves heaves wildly, and one monster billow after
another, perhaps twenty feet in height, reaching far
along the line of shingle, rolls fiercely up, curls grandly
over, and falls with a deafening crash, sending forth a
rush of foam and spray, grinding the pebbles together
and tossing them about like sand. No human being
could live beneath the crushing weight of one of those
waves. ‘The noise is so deafening, in even a moderate
gale, that I have tried in vain to hear words shouted in
vigorous masculine tones close at my side. Ina storm,
so mighty is the turmoil, that a small brig has been
actually lifted by the sea, carried over the top of the
ridge, and landed on the shingle slope beyond, whence
a way was made for it later into the quiet bay.

The action of the wind upon the ocean surface
varies much in different places. A greater contrast
could hardly be found than between the vast majestic
rollers of the Atlantic, a quarter of a mile or more
apart, travelling in slow succession, and the broken
chopping waves of the Channel, dashing into and over
one another with impatient and undignified restless-
ness. Again, one may turn from the stately water-hills
of the sea off the Cape of Good Hope, forty feet or more
from crown to hollow, calm in motion and deep-blue in
hue, to the wild perilous turmoil of the North Sea.

One or two quoted descriptions of the latter will
speak more forcibly than any words of mine can do, as
186 The Ocean of Air.

to the awful power of the wind over the ocean, and of
the ocean over aught that lies in its grasp.

‘The gray fitful waves roll over the Dogger, and
the steady shrill wind is lulled but seldom. The sea
does not run true, and sometimes after a succession of
glossy rollers has travelled westward, there comes a
furious northerly drift, which is met by a swift whirling
current from the south; the charging waves meet in
thunder, the rearmost seas climb in foaming piles over
the shattered bulge of those that reel back from the
onset, and the wild hurly-burly lasts until the strong set
of the westerly roll masters the leaping cross-drift, and
then once more the gray sliding procession moves in-
exorably shoreward.....

‘In December, 1883, there was another storm that
will not soon be forgotten. To say that there was a
heavy sea expresses nothing; that tremendous convul-
sion passes the power of descriptive words. ful steam-carrier was hit by one unlucky sea, which not
only burst her, but shivered her into tiny scraps; strong
wire ropes were snapped like worsted ; wire stays which
held well tore up great lumps of the bulwarks, and the
amazing force of the sea was shown by the fact that
the wood of the torn bulwarks was cut as cleanly as if a
huge knife had shorn through. . . . Yarmouth, Lowes-
toft and Grimsby harbours looked as if they had been
under heavy shell fire for many days after the gale;
hardly a boat escaped without serious damage, and the
wonder is that any of the fleet got home.’*

And again from the same pen:

‘The wind met one like a solid body, and its savage
storming call stunned the nerves. . . . It piled up a sea
much worse than several I have seen when a perfect

* J. Runciman.




Waves breaking over the Sea Wall at Bognor. From a photograph by W. P. Marsh.


More -about the Wild Winds. 187

hurricane was blowing. Then the run of the sea was
cross-grained, and when two or three charging currents
met they reared up into a hill that fell away like a water-
spout. . . . Finding that it was impossible to see any-
thing save a dark flurry of tortured water, or to hear
anything save the numbing thunder of the gale, I tried
to snatch some sleep, but it was a hopeless attempt.
The vessel was riding beautifully ; sometimes when it
seemed as if she must actually fall off the side of a sea,
she sidled prettily up the flank of the gloomy threaten-
ing mountain, topped it Jike a bird, and swept down the
rushing slope, without so much as shipping a splash of

‘Harder and harder the wind blew; the rearmost
waves strove to climb over the front ranks; the blown
spray cut like sharp lashes, and the ugly hills that were
veiled by that cruel drift made bellowing sounds as they
rushed on their sliding bases. Imagine the Brighton
downs magnified; imagine also the surface of the downs
covered by tumbling hillocks, and then imagine two or
three of the bluffs of the downs terraced one above
another, and you have an image of such portions of
that sea as the eye could take in at one view. The
bright strength and speed of the torn rollers were
splendid; but I felt rage in my heart, as I thought that
those beautiful awful waves might kill some of the poor
fellows who had been sent out in rickety ill-found
vessels.’

Such word-painting as this makes even a landsman
able faintly to realize what it is to be out on the North
Sea when the winds are in their rougher moods.

But to learn the uttermost strength of the soft air
to lift and wreathe the ocean surface into death-dealing
waves, we must go to the tropics.
188 The Ocean of Atr.

On the 31st of October, 1876, more than a million
human beings, natives of India, lay quietly down to
sleep, on certain flat lands about the mouth of the
Ganges, after it is joined by the Brahmapootra, and
on certain low-lying islands at its mouth. The islands
are built out of the soil which is constantly carried
down by those two great rivers.

The people counted themselves safe that night, as
safe as usual. No particular fears troubled them.
They knew that these low unprotected lands were
subject now and then to sudden inundations from
storm-waves, lashed up by a circular hurricane on the
ocean, and brought to their shores; but such cata-
strophes were only occasional. They had taken pre-
cautions, they had built their little huts on platforms
or mounds of earth some three feet in height, and they
counted themselves fairly secure.

At ten o’clock a storm raged, but without any un-
usual features: one of the ordinary cyclonic storms of
the tropics.

But at the hour of midnight came an awful warning
cry, passed on from man to man, and overtaken by the
hurrying foe, ‘ The water is on us!’

One cyclone-wave after another, drawn up at sea
in the whirlwind centre, was launched ruthlessly by
the fierce gale over the islands and the low-lying
mainland. The rushing tide bore all before it. No
less than three thousand square miles of country lay
soon under water from ten to twenty feet at least in
depth.

Little use were the hut-platforms against this
mighty incursion. Thousands of the inhabitants died
at once, died in their sleep, or woke to a moment’s
agony before they perished. Some climbed the trees
More about the Wild Winds. 189

near their huts; others were flung by the rough billows
into the branches; some floated on the roofs of their
huts, torn away from the mud walls, and others clung
to logs of wood; but too many of these were carried
hopelessly out to sea.

The flood did not last long. By morning it was
subsiding, and by noon the unhappy refugees in tree-
tops could descend. But wind and wave had done
too surely their fearful work. Two hundred and fifteen
thousand human beings were destroyed in one half-
hour, by a single fell swoop of the elements.
CHAPTER XXII.
THE GREAT WATER-CIRCULATION.

It is hardly possible to gain a clear idea of Water-
Circulation generally, without a few words first on the
subject of ocean-circulation.

These two fluids, Air and Water, are intimately
bound together. So intimately, that neither can be
long viewed without some reference to the other.

The two Oceans, that of Air and that of Water, are
to a very great extent governed by the same laws.
Far more so than we, living at the bottom of the Air-
Ocean, would naturally suppose.

Water, as water, wherever it may be, always strives
to keep its own level, to present a perfectly even upper
surface. Whether a mass of water be large or small,
it can never remain at rest with one part of its surface
higher than another part. Astream immediately flows
from the upper to the lower surface, to restore the
lost level.

This is much the same as we have seen in the
Ocean of Air.

True, we do not talk of a gas or a portion of air
‘keeping its level,’ since a gas can spread out equally
well in all directions. But when we consider the
Ocean of Air, as a whole, we find it following almost
the identical rules of an ocean of water. The manner
The Great Water-Circulation. IgI

in which it flows to and fro to preserve above what
may perhaps be called ‘a level surface,’ at all events
to arrange that equal quantities and weights of air
shall be over all parts of earth’s surface, has been
already explained.

Another rule is common to the two Oceans.

We have seen, in the circulation of air, how every
current of air makes needful a second or counter-current.

It is the same in the circulation of ocean-waters.
Every current of water flowing one way makes needful
a second current the other way. Just so much water
as passes from the north to the south, must also pass
from the south to the north. Just so much water as
pours towards the equator must also pour away from
the equator. If not, all ocean-waters would gradually
collect in a vast heap upon one part of the ocean-bed,
while other parts would be left dry.

Many causes combine to keep the ocean in ceaseless
unrest.

Winds blow over its surface from all quarters of the
compass, bearing the surface waters with them. Un-
equal heating of one part and another, causing some
waters to expand and grow light, while others remain
cold and heavy, is a fruitful source of currents, Vast
quantities of water are daily drawn up by the sun into
the atmosphere from one place, to be poured down
in another, thus further disturbing ocean’s balance.
Mighty rivers rush from the land, each making fresh
readjustment needful. The tides sweep to and fro,
day after day, stirring up the great expanse anew.
Such and countless other disturbing forces render a
petrified and changeless ocean impossible.

‘He causeth His wind to blow, and the waters
192 The Ocean of Air.

flow.’ These are words written very long ago, yet

true now as then.

The power of winds to produce currents in the
ocean has been often questioned. But there can be no
doubt that such persistent winds as the trades have
great influence in causing steady and continuous
surface-drifts.

Each of the five chief oceans has its own separate
circulation, the entire mass of water moving slowly
round in an enormous eddy before going on elsewhere.

A most weighty part in the Atlantic eddy is played
by the Gulf Stream.

It seems strange to think of an actual river in the
ocean, yet many such rivers exist. The Gulf Stream
is an actual river of warm water, flowing north-
ward out of the tropics, upon a bed of cold water, with
cold water banks. The distinction between the warm
Gulf Stream waters and the cold ocean waters is so
sharp that a ship may lie across, half in the stream,
half in the ocean, the line of separation being plainly
seen.

The Gulf Stream waters are not only much warmer,
but much salter, and therefore of a much deeper blue
than the ocean waters.

If water gained and lost heat as quickly as land
does, the Gulf Stream would be of very little use to us
in the British Isles; but happily it is not so. The
thick underlying cushion of cold water keeps the Gulf
Stream from the ground, which would fast steal its
warmth, and so it pours on to British shores, holding
still a good deal of its tropical heat.

On first leaving the Gulf of Mexico, the stream
is about thirty miles wide, and moves at the rate of three
hundred:and sixty feet.each hour. By the time it has
The Great Water-Circulation. 193

wandered as far north as Newfoundland, it is over three
hundred miles in breadth, and moves much more slowly;
yet it is still distinct from the ocean.

We may see in the Gulf Stream a remarkable illus-
tration of that enlarging which was spoken of a little
earlier in connection with heated air over a desert and
over the tropics.

The waters of the ocean-river, being much warmer
than the waters of the ocean around, expand or swell
outwards. The central line of the Gulf Stream off
Hatteras stands about two feet higher than the ocean
level, partly indeed from rapid motion between con-
fining banks, but partly also from the increased
bulk of the heated water. In consequence of this, per-
petual surface-streams pour from the top to either side.
Colder and heavier waters find their way in below, and
the bottom of the Gulf Stream is gradually forced
upward, the stream flowing in a bed which steadily
widens and grows more shallow.

The swelling of the heated water, the two outflow-
ing surface-streams above, and the two inflowing cold
currents below, seem to be on a smaller scale very
much the same that we have seen to take place in the
Ocean of Air over the equator, resulting in trades and
anti-trades.

So distinctly does the surface slant downward to
either side, that floating seaweed and drift-wood are
known never to find their way across the Gulf Stream.
They cannot do so, for they would have to climb a hill
and ridge of water.

‘All the rivers run into the sea; yet the sea is not
full; unto the place from whence the rivers _ ome,
thither they return again.’

13
194 The Ocean of Air.

That is ‘precisely what happens. All the rivers;
speaking generally, run into the sea. With the excep+
tion of the Jordan, flowing into an inland sea, and
a few like instances, all rivers find their way, not only
into ‘the sea’ of any particular country, but into ‘ the
sea ’—the great ocean.

‘Yet the sea is not full” The ocean waters: are
under restraint. ‘They do not rise up to swamp and
overpower the lands,—as probably they might, if all the
water that exists in earth and air found its way to the
ocean and remained there. But ‘from whence: :the
rivers come, thither they return again. ‘

Where do the rivers come from ?

In a great measure from hill-tops and mountain:
ranges. Water collects on high lands, falling from the
clouds, draining from snowfields. It pours downward
in streams, which, joined by other streams, grow, into
torrents, and swell into rivers, running ‘into the
sea.’

What next? These rivers return — how and
where ?

They become part of the ocean first. The water:
particles which formed the rivers on land now flow ito
and fro in ocean-currents. For awhile perhaps they
are far down in ocean’s depths, away from sunlight.
Sooner or later, they find their way towards the sur-
face. By-and-by, while there, exposed to the sun’s
heat, they pass upward into the air as invisible
vapour.

Then the air carries them over the land, and the
heated ground warms the air, making it expand and
rise upward ‘like wood plunged in water ’*. through

* Tyndall
The Great Water-Circulation. 195

heavier air overhead... So rising it grows cold again,
and can no longer contain all its moisture.

The once river-particles are next pressed gently out
of the air as a little mist, and they go to join a cloud
near. The cloud is borne by air currents to and fro,
till perhaps it reaches the very same mountain from
which ran the river which brought these water-particles
down to the sea.

The cold mountain-peak cools still farther the air
in which the cloud rests. Then heavy showers of rain
fall, soaking the earth, filling the rills, and feeding the
rivers which run into the sea.

Or the mountain and cloud are both so high up in
the air that the cloud is frozen, and snow falls instead
of rain. It comes to the same thing in the end. The
snow drains out in a river of ice, and the river of ice
becomes a river of water.

Now we see how true it is that ‘from whence the
Tivers come, thither they return again.’

Do they come from mountain ranges? Mountains
receive far more plentiful supplies o7 rain and snow
than level plains. The rain and snow combine to feed
the rivers. The rivers feed the sea. The sea feeds
the air. The air feeds the clouds. The clouds empty
themselves upon the mountains.

Do the rivers come from the clouds? That is
equally true. Clouds pour down rain. Rain fills the
rivers. The rivers supply thesea. The sea-surface dries
into the air, as vapour. The vapour becomes clouds.

So, whether we start with mountain rivulets or with
clouds, the circle is complete, and we come always
round to our starting-point.

The whole world—land and ocean and atmosphere

3—2
196 The Ocean of Air.

—has been described as ‘a vast distilling apparatus.”
The warm south seas serve for its boiler; the sun is
its furnace; the colder regions, north and south, are
its condensers. We may talk of the atmosphere as a
huge pumping-engine for pumping up and showering
down water. But the atmosphere does not and cannot
act alone. It works in company with land and ocean
under the sun’s control.

Tropical oceans, steadily heated by the sun’s rays,
send streams of vapour into the air. These streams of
vapour pass upward, with the steadily-ascending air of
the Equatorial Calm Belt.

Air, as it rises, becomes colder. Not merely because
the upper regions of the atmosphere are colder, but be-
cause the lessened weight of air above makes it expand,
and in this act of expanding or stretching a certain
amount of heat is given out.

Now, the air growing colder becomes virtually
damper. Not actually damper, because it does not
contain more vapour than before, but virtually damper,
because it is more nearly saturated, more nearly obliged
to part with some of its hidden vapour. The next
stage is that it does reach saturation-point, and does
lose moisture, which is poured down as heavy rain.
The torrents of rain peculiar to the Calm Belt of the
equator were described earlier.

Having parted thus with a goodly amount of
vapour, the air, still mounting, reaches that level in the
atmosphere where the anti-trades flow to north and
south. : .

It used to be supposed that the high-level currents
from the equator carried away immense supplies of
moisture, to be poured down as rain over the temperate
The Great Water-Circulation. 197

zones, beyond Cancer and Parra ae the south
of Europe, for example.

This view is now held with more reserve. No
doubt the anti-trades do contain a certain amount of
vapour, even after sending down abundant torrents
near the equator. Great cold, however, rapidly con-
denses moisture into cloud and rain; and these
tropical currents, before starting for the north or
south, reach very high and very cold regions of the
atmosphere.

They cannot, therefore, be supposed to bear away
any enormous amount of tropical vapour. The cold
‘which they encounter in temperate countries, even in
winter, can hardly exceed the intense cold of those
lofty air-levels above the topmost mountain-peaks ever
climbed by man. Whatever moisture the anti-trades
still hold, when they come down to earth beyond the
tropic of Cancer, can hardly be distilled into cloud or
rain by the cold of southern Europe. It would rather
be carried away to the far north, there to feed the
Arctic snow-fields and glaciers.

In an earlier chapter the atmosphere was spoken of
as a huge invisible sponge, always resting on the ocean
and becoming filled with water. Near the equator the
sponge gets well saturated. Then, passing upward, it
has a very severe squeeze from the intense cold of
higher regions, which sends down rain in torrents.
After that violent squeeze, one would scarcely suppose
the sponge to be sensitive to further squeezes from the
soft air of south Europe.

In all these operations, as said earlier, the real
working-power is the sun. The atmosphere without
the sun would be as the steam-engine without furnace-
fires—a very perfect machine, no doubt, but powerless
198 The Ocean of Air.

to act. Air is simply the machine or engine through
which the sun acts.

~The. task carried out by sun and air is indeed no
slight one. To raise daily tons upon tons of water out
of the ocean ; to lift these mighty masses high, not in
one convulsive heave, but calmly, gently, noiselessly,
with no sign of effort or strain; to bear them to and
fro lightly, as a leaf is carried by the wind; to pour
them down again on land and sea, not in one death-
dealing cataract, but in showers of separate drops—
this is what has to be done, what is done, day after
day, by the great sun and the obedient air.

But for the sun, we should have no drying up of
moisture, no clouds, no rain. Nay but for the sun, we
should have no glaciers or snowfields.

For glaciers are fed by snowfields; snowfields are
fed by clouds; clouds are fed by invisible vapour in the
air ; vapour is lifted out of the sea into the air by the
sun. So without sun-heat there could be no floating
vapour ; without vapour, no clouds; without clouds, no
snow ; without snow, no glaciers.

A curious chain of causation !—distinctly proving
that the ice-rivers of Switzerland and of the Arctic
regions have their origin in the heat of the sun.

Indeed, the greater the power of the sun in the
summer of southern lands, the larger are the supplies
of vapour drawn into the air. The greater the amount
of vapour carried by winds against mountain ranges or
into the north, the heavier will be the snowfall. An
exceptionally hot summer is often followed by an
exceptionally cold winter, while a cooler summer
means often a warmer winter to come.

So round and round, in and out, the Water-Circula-
tion continues. Out of the sea into the air; out of the
The Great Water-Circulation. 199

air into clouds; out of clouds down upon earth; from
‘the earth into the ocean! Or, out of snow into water,
out of water into vapour, out of vapour into a snow-
cloud, out of a snow-cloud into snow! The course of
changes, the chain of events, may be differently told.
Either way, it is a circular chain, without apparent
beginning or end,
PART V.

DISTURBANCES OF THE AIR-OCEAN,
CHAPTER XXIII.
CLIMATE.

BETWEEN the Equator and the Poles every description
of Climate is to be found. From intensest heat to
intensest cold, from utter dryness to utter wetness,
from perpetual wind to perpetual calm—any variety
may be had.

‘From Greenland’s icy mountain to India’s coral
strand’ is a leap which the poet may make in imagina-
tion. The traveller can take no such leap in body, but
must pass through stage after stage, leading from one
extreme to the other. It is only in fancy that we see
side by side, sharply contrasted, hot and rainless Egypt
with. mild and rainy Ireland, Africa’s burning plains
with the vast ice-fields of Greenland, the awful heat of
the Persian Gulf with the awful cold of Siberia, the
continuous rains of the tropics with the fitful showers
of temperate lands, the severe cold and heat of Canada
with the moderate seasons of England. These and
countléss opposites, all upon one globe, come under the
head of Climate.

Climate deperids chiefly upon degrees of heat and
cold, degrees of dryness and moisture, degrees of wind
and calm. In other words, it depends upon the state of
the Air.
204 The Ocean of Air.

Human beings, taken generally, manage to bear
pretty severe extremes of heat and cold.

Some of the very coldest spots inhabited by man are
to be found in the Dominion of Canada, and in that
awful country of exiles, Siberia. A hard-working Cana-
dian Bishop of the Anglican Communion, now living,
has in the care of his diocese slept for ten days ata
time in the open air, with the thermometer 40° below
zero. Pretty severe this for a man well on in middle
life! He might indeed say, ‘You in England don’t
know what it means.’ We counta winter exceptionally
severe if the mercury stands for any length of time at
20° to 25° above zero.

But even the Bishop’s experiences are outdone by
what unhappy Russian exiles have to endure at certain
Siberian ‘stations — only his is MOlnutary endurance,
theirs compulsory.

At one-of the said stutond, Weichajunsle the
thermometer stands habitually, through December and
January, at 56° below zero, and often sinks much lower.
It sometimes descends to 81° below zero.

Turning to the Red Sea for a glance at the opposite
end of the scale, we find that at Massowah, during
May, the thermometer has been known to stand, as an
ordinary event, at about 99° above zero in the shade,
occasionally running up to 130°.

As a rough rule, farther north or south from the
equator means increased cold. There are successive
bands of climate round the earth, zones of heat being
followed by zones of mildness, then of moderate cold,
iastly of extreme cold. Each zone has its own
peculiar plants, and more or less its own peculiar
animals. Animals have a wider range than plants,
being better able to adapt themselves to varieties of


Snow on the Slopes of the Himalayas. From a photograph by
Shepherd & Bourne.
Climate. 205

climate ; but perhaps man alone can live in almost all
climates.

It might be expected that the bands of climate
round the earth would lie in regular order, so much
less of heat matching so many miles further to the
north. But under the modifying influences of air and
sea, things are very different. Stiff lines of latitude
drawn on a globe will not at all fit in with lines of
climate.* The latter are indeed most erratic. Instead
of following the straight and even latitude lines, they
run farther north here, and farther south there; take a
sudden bend; make an unexpected twist ; do anything
in short, except keep to such rules as we should expect.
But for every bend and twist and loop there is a sufficient
cause.

Differences of climate depend first and chiefly upon
the position of the sun in the sky—upon whether the
sun’s rays come straight down from above, or slanting

* ‘Climate-lines,’ drawn ona map or chart, are called isotherms,
or isothermals, or ‘curves of equal heat.’ They are drawn in dif-
ferent modes, but always under the guidance of the thermometer.
Sometimes the averages of a whole year are taken—to be noted,
let us say, on a map of Europe and North America. Each day
through the year, the height of the thermometer at certain hours
in certain stations is noted. At the year’s end, the results are
added up and divided by the number of observations, to find the
average, or medium height, for the whole year at each station.
Lines are then drawn upon the map, from place to place, where-
ever the average height of the thermometer is found to be the same.
One line marks all stations where the average was 40°, another
where it was 50°,andso on. These lines are not straight and even,
like lines of latitude, but they bend and curve: for some places
farther north are warmer than other places farther south. A par-
cularly big loop may be observed just to the west of Europe, which
is altogether warmer than corresponding latitudes across the
Atlantic. The same calculation may be made, not for the whole
year, but for one month—for January or June. The lines drawn
will then show the average warmth of certain places in the height
of summer or in the depth of winter.
206 The Ocean of Air.

from near the horizon, Within the tropics the sun is
always more or less overhead ; and in Polar regions he
is never overhead. In the summer of temperate lands
he is high up; in the winter, and also in the mornings
and evenings of summer days, he is low down.

Now in the latter case, a sunbeam has to travel a
very much longer way through the dense damp lower
layers of air. A great deal of heat is stolen from it by
the air on its road, leaving little to reach earth’s surface.
But when a ray darts downward from overhead, it
travels through a far smaller amount of damp air; so
it loses much less of its heat.

However dazzling the sun may have been overhead,
on a hot summet’s day, we are able commonly to look
full at him, without blinking, when he gets near the
horizon. A far thicker veil of floating moisture cuts off
the chief part of his light and heat from our eyes.

Another cause, besides the position of the sun in the
sky, greatly affects climate. This is, the manner in
which the sun’s rays are received.

The great sun acts with most impartial regularity,
pouring down his beams alike on ground, on ocean,
and on atmosphere.

But there are two things to be considered in think-
ing about the power of a sun upon a world. One is—
how the sun bestows his beams; the other is—how the
world is affected by those beams.

If earth’s whole surface were everywhere exactly the
same, then the sun’s rays would take effect everywhere
exactly alike. Since it is made of different kinds of
substance, partly solid and partly liquid, with a varying
veil of more or less damp air above, this cannot be the
case.

Dry ground receives heat quickly, and parts with it
Climate. 207

as quickly. Water receives heat slowly, and parts with
it as slowly. Air receives and parts with heat more or
less quickly and slowly, according to its degree of dry-
ness or dampness.

We see the same thing, curiously enough, in human
beings. What a man takes in with great ease, he is
apt to forget with ease; and what he gains mentally
with toil and effort, he does not soon lose.

Water’s slow gaining and long keeping of warmth
modifies immensely the climates of earth. Mighty
ocean currents, pouring north or south from the tropics,
carry tropical heat with them to colder parts, and make
countries which would be frost-bound for months rejoice
in continuous mildness.

But seriously as ocean’s moving waters must and do
affect climate, their influence would be far less without
the help of moving air. For, after all, the waters can
do little more in themselves than wash the shores of a
country. Their really effective work is to warm the
atmosphere above, so that currents of air passing from
the ocean over the land carry heat with them.

Two or three extracts from travellers’ reports may
help to bring before the mind what is meant by earth's
varieties of climate.

As variety No. I, we find in the life of Colonel E.
Warburton, the following account of Australian desert
heat, experienced by travellers camping in a small oasis:

‘The depot was shaded by large trees, and by high
cliffs, notwithstanding which the party suffered terribly
from the intense heat. The mean of the thermometer
for the months of December, January, and February,
was Iot°’, 104° and Io1° respectively in the shade.
Under its effects every screw in their boxes had been
208 The Ocean of Air.

drawn, and the horn handles of their instruments, as
well as their combs, were split into fine lamine. The
lead dropped out of their pencils, owing to the shrinking
of the wood; the signal-rockets, a most valuable item
in the equipment of the expedition, were entirely spoiled;
their hair, as well as the wool on the sheep, ceased to
grow; and their nails became brittle as glass. Nor
was personal inconvenience all the mischief wrought by
this fiery atmosphere, for it was found to reduce the
provisions alarmingly. The flour lost more than eight
per cent. of its original weight; the bran in which their
store of bacon was packed became perfectly saturated,
and weighed almost'as heavy as the meat; they were
obliged to bury their wax-candles, to save them from
running into a shapeless mass; even a bottle of citric
acid became liquid, and, escaping, burnt some linen ;
whilst it was with the utmost difficulty that they could
either write or paint, so rapidly did the fluid dry in the
pens and brushes. During the whole of this trying
period, the leading members of the expedition never
ceased in their attempts to find some means of escaping
from this oven. To east, west, north and south, they
rode, the heated stirrup-irons blistering their feet, and
the horses reeking with perspiration, though never put
beyond a walk.’

Again somewhat later we find:

‘Captain Sturt ... returned to the depdt, and
after resting started off afresh, discovering Cooper’s
Creek, beyond which he encountered his old enemies,
the sand-ridges. He mentions the effect of a hot north-
east gale. The blasts of heat were so terrific that he
wondered the grass did not fire. This was nothing
ideal, for everything both animate and inanimate gave
way before it; the horses stood with their backs to the
Climate. 209

‘wind, and their noses sunk upon the ground, without
the muscular strength to raise their heads; the birds
sat upon the boughs, mute and terrified; and the
parched leaves fell like snow; whilst a thermometer
graduated to 127° burst its tube, owing to the expansion
of the mercury. Before fresh supplies reached them,
the leader had lost the use of his limbs from scurvy;
this skin became black, and the muscles contracted.’

In contrast with the above, as a specimen of Climate-
Variety No. 2, let us turn to Captain Scoresby on the
Arctic regions.

‘An Arctic winter consists,’ he writes, ‘of the
accumulation of almost everything among atmospheric
phenomena that is disagreeable to the feelings. ....
The Greenland sailors, being well defended from ex-
‘ternal cold by a choice selection of warm clothing,
generally support the lowest temperature after a few
days’ habitude without much inconvenience. When,
however, its attacks are not gradual, as when a ship,
which has attained the edge of the ice under a
‘southerly gale, is exposed suddenly to a northerly
breeze, the change of temperature is so great and
rapid that the most hardy cannot conceal their un-
easiness under its first impression. On one occasion,
‘in the year 1814, there was between the time of my
leaving the deck at night and arising the following
morning, an increase in the cold of about 20°. This
remarkable change was attended with singular effects.
The circulation of the blood was accelerated, a sense
of parched dryness was excited in the nose, the lips
were contracted in all their dimensions . . . and the
articulation of many words was rendered difficult... .
The hands, if exposed, would have been frozen in a

14
210 The Ocean of Air.

few minutes. . . . A piece of metal. when applied to
the tongue instantly adhered to it, and could not be
removed without its retaining a portion of the. skin;
iron became brittle. .. . The ship became enveloped
in ice ; the bows, sides, and lower-rigging were loaded.”

Mean with reference to some seamen who wintered
in Spitzbergen :

‘After the commencement of the new year, the
frost became most intense: it raised blisters in their
flesh, as if they had been burned with fire, and if they
touched iron at such times it would stick to their
fingers like bird-lime.’

Mr. Ballantyne’s account of winter in Hudson's:
Bay is to some extent an echo of the above:

_ ‘ After that (October), until the ;following April, the
thermometer seldom rises to the/ifreezing-point. In
the depth of winter it falls from 30° to.40°, 45° and evem
50°, below zero of Fahrenheit. This intense cold,
however, is not so much felt as,one, might suppose,.
as during its continuance the air is perfectly calm.
Were the slightest breath of wind to, arise, when the
thermometer stands so low, no:-man could show his
face to it for a moment. . .. The: houses are built
of wood with double windows and doors. They are
heated by means of large iron stoves fed with wood ;
yet so intense is the cold, that I have seen the stove
in places red-hot, and a basin of water in the room
frozen nearly solid.’

In pleasant contrast with these violent extremes,
a few words from Miss Gordon Cumming’s ‘ First
Impressions of Fiji’ may serve well for Variety
No..3:

‘As regards climate our impressions are highly
Climate. 2II

favourable. We see white men, who have becn here
for years, going about without any of the ordinary
precautions deemed necessary in tropical climates.
White umbrellas and solar hats are alike neglected,
and a white puggaree is considered ample protection
in a country where sunstroke and fever are alike rare.
The thermometer at go° marks an exceptionally hot
day, and with the exception of occasional tropical
showers we have generally fine weather ; hot certainly
in the mid-day hours, but almost invariably tempered
by a balmy breeze and soft gray clouds. December
is supposed to usher in midsummer heat and heavy
rains—not incessant, but very much in earnest while
they last—and for three months we may be liable to
hurricanes, which, however, are not an invariable part
of the programme; nor can they possibly be as severe
as those of the West Indies, or all the frail buildings
which compose this little capital would inevitably have
long since been levelled with the ground.’

The thermometer has been often spoken of in
this chapter. A thermometer is a measurer of heat,
and Climate is largely a question of more or less heat.

The little instrument consists of a glass tube ending
below ina glass bulb. It contains enough mercury to
fill the bulb and part of the tube, the rest of the tube
being partially emptied of air.

Mercury is quickly affected by heat and cold.
When the surrounding air is very hot, the mercury
swells in size, more rapidly and to a greater extent
than the glass, so the slender line of it in the tube
gently rises. When the surrounding air is cold, the
chilled mercury grows smaller, takes less room, and
sinks lower in the tube.

14—2
CHAPTER XXIV.
WEATHER.

CLIMATE and Weather are closely related, but not
identical.

For questions of Climate we turn mainly to the
thermometer. For questions of Weather we turn
mainly to the barometer. Yet the state of the
barometer has also a very intimate connection with
the climate of a place, and the state of the thermometer
‘with its weather.

On the whole, ‘weather’ is a word more used
with reference to the temperate zone than the tropical
regions.

Where the sun blazes day after day, for months, out
of a blue sky, with no change or sign of change, men
do not say, ‘What beautiful weather!’ but rather,
‘What a sunny climate!’ Just as day and summer,
night and winter, merge into one at the Poles, so
climate and weather merge very much into one within
the tropics. The very rain comes, when it does come,
with a regularity which speaks rather of climate than
of weather.

ln our temperate regions, our northern belt of
‘variable winds,’ while climate has certain persistent
outlines which may be reasonably calculated on,
Weather. 213

weather seems to be a thing of impulses, altogether
erratic.

Yet our weather, like all else in Nature, is governed
by settled laws. Weather in England is not more
really fitful than in the tropics. It is only uncertain
in respect of our ignorance. The many forces which
combine to bring about varying results are more com-
plex than the broader and simpler rules which govern
tropical weather, and are not so well understood by
man. None the less, every change of breeze, every
passing shower, every cloud which forms and vanishes,
has had its causes leading up to the present moment.

One main foundation of climate is the heat of
the air, in varying degrees. A main foundation of
weather is the weight or pressure of the air, in varying
degrees.*

As the warmth of the air is measured by the ther-
mometer, so the pressure of the air is measured by the
barometer.

A barometer, like a thermometer, consists of a
glass tube holding a column of mercury, the upper
part of the glass being as far as possible emptied of
air. Here the resemblance ceases, for the mercury-
column rests in a little vessel open to the air, and the
atmosphere pressing upon the exposed mercury keeps
the slender column upright in the tube, just so high as
to balance its own heaviness.

If the pressure of the air weighs exactly the same
as a column of mercury twenty-eight inches high, then
the mercury-column will stand exactly twenty-eight
inches high in the tube. If the air presses harder it
will push the mercury-column higher; if less hard it
will let the mercury-column sink a little lower.

* See Chapter III.
2I4 The Ocean of Air.

A barometer, examined first at the sea-level and
then carried up a mountain, will be found on the
summit to tell of greatly lightened air... For the denser
layers have all been left below, and. the pressure is in
consequence much lessened.*

Even at the sea-level the pressure is by no means
always the same. Air there is sometimes lighter through
warmth, sometimes heavier through cold. Also currents
of air, especially those which flow upward and down-
ward, have a good deal to do with degrees of pressure.

In the last chapter we heard about certain charts
. on which are drawn climate-curves,t or curves of
equal warmth in different places.

Charts are made in like manner for the drawing of
weather-curves,{ or curves of equal air-pressure in
different places.

Very often a chart§ is made which is a union of
the two. Upon a map of a certain district are drawn
the climate-lines of a certain date, as shown by ther-
mometers, and the weather-lines of the same date, as
shown by barometers. The map is then filled in with
symbols of rain and fine, wind and calm, occurring in
different parts. Thousands of such records have been
taken during the last few years.

Weather-curves are even more fitful and curious
than climate-curves. The latter do at least wave and
zigzag round the earth, keeping in some sort of fashion
in one chief direction. But the weather-curves run
fantastically all ways, and form most singular shapes.

* On the top of Snowdon the mercury rises only 264 inches‘;
and on higher mountains it stands still lower.
+ Isotherms.

t Isobars.
§ A Synoptic Chart.
Weather. . 215

Not any and every kind of shape, however! Even
here we find rules apparently laid down and carried
out. Even the wild winds have-method and order
stamped into their very being.

These weather-curves when drawn upon the map
fall commonly into one or another of seven* distinct
shapes, or classes, known one from another by a prac-
tised eye. Some of them, such as cyclones and anti-
cyclones, are familiar to us all by name.

Now, nothing is easier than to turn disdainfully

away and say, ‘Of course! Anybody may draw any
lines upon a map, and make what shapes he pleases.’
' But these are not fanciful outlines. They follow
strictly the actual readings of barometers all over a
certain district at a certain time. Each barometer-
reading shows the exact pressure of the air just when
and where it is noted, and that degree of pressure
always means something: definite about the weather,
though what it means is not always clear to us.

Distinctly as the beating of your pulse shows the
state of your health, the rise or fall of the barometer
shows the condition of the atmosphere in respect of
its pressure. Reading the barometer is feeling the
pulse of the air. But not everybody with eyes can
read a barometer truly, any more than everybody aes
fingers can feel a pulse understandingly.

A man, seated in a central office, receives news at
once from'many stations. In some of these stations
the mercury stands, let us say, one particular morning,
at 29°6°, in others at 29°8°, in others at 30°0°. On his

* A Cyclone, an Anti-cyclone, a Secondary Cyclone, a Wedge,
a V-shaped. Depression, a Col, a Straight Isobar. From these
seven fundamental or simple Weather-shapes, are produced many
moditied varieties,
216 The Ocean of Air.

map he draws lines from place to place of the first ; from
place to place of the second ; from place to place of the
third. He does not follow any private notions of his own,
but simply obeys the readings of barometers. These
lines when drawn form certain shapes ;* and the shapes
speak of certain actual realities in the Ocean of Air.

One can well imagine that curves so drawn, dictated
as one may say by the freaks of the wild winds, might
fall into any manner of shapes, never turning out twice
the same. Yet it is far from being so! The wild winds
show ‘method in their madness.’ These shapes do con-
stantly turn out so far alike as to be easily classified.
Moreover, each kind of shape has a more or less dis-
tinct kind of weather belonging to it.

The Air-Ocean, as we have already seen, is never at
rest.- It isin a condition of perpetual whirl and tur-
moil. Circulating currents stream to and fro. Winds
pour this way and that way. Eddies and ripples in-
numerable cover the face of the earth. A ceaseless con-
flict of forces goes on. Rivers of air to the north are
balanced by rivers of air to the south. Heat strives
with cold; and evaporation strives with condensation.
Heavy air rushes towards light air, and ight air flees
from heavy air.

In the flow of a great river, there is the general
movement of the whole body of water from a higher to
a lower level. There are also countless lesser flowings
to and fro; eddyings round obstructions; silent pools ;
calm stretches ; broken waves and rapids. As theriver

* ‘Tsobars represent the effect on our barometers of the move-
ments of the air above us, so that by means of isobars we trace the
circulation and eddies of the atmosphere.’—Adercromby.

‘The seven fundamental shapes of isobars are, as it were, the

product of so many various ways in which the atmosphere, circu-
lating from the equator to the poles, may move.’—J/dd.
Weather. 21’

runs, its surface has various risings and depressions ;
its waters pour many ways, which might be indicated:
by shapes drawn on paper.

So too with the atmosphere. There are the mighty
main-streams below and above. There are also back-
streams, side-streams, lesser currents, circlings to and
fro, heights and depressions of the outer surface, waves
and eddies innumerable.

One may see baby-eddies of air in the road ona
windy day, tiny whirls of air carrying round dust and
leaves. A cyclone is such an eddy on a large scale,
varying from fifty to over two thousand miles across ;
and other air-disturbances are more or less of the same
nature.

An eddy of water may be either fixed or in motion.
A river-eddy is often long motionless. Water-particles
pour in, circle round, and pour out again, while the
eddy itself is unchanged. But some river-eddies, and
most ocean-eddies, travel onward from one_ spot
to another, forming and vanishing after a fitful
fashion.

There are eddies of air which remain motionless, —
as well as eddies of air which move. Anti-cyclones
are often stationary for hours and days, even for weeks
and months. Air-particles flow in and out of the
stationary anti-cyclone, but the great eddy itself, gently
circling, is fixed in one place. Some anti-cyclones
travel like other eddies; some form, stay for awhile
where they are, then break up.

As a rule, air-eddies are given to moving on. A
cyclone, like an ‘anti,’ may form anywhere and break
up anywhere; but it almost always journeys, sometimes
travelling straight forward, sometimes creeping round
the edge of a fixed anti-cyclone.
218 The Ocean of Air.

This drifting over us of air-eddiés is “a fact which
ought to be clearly grasped.

Weather comes to us; we do not go to it. Man
stands still, so to speak, and different kinds of weather
sweep past. A cyclone-comes to give him rain; an
‘anti’ comes to give him:sunshine. - Each in turn drifts
onward elsewhere, to be replaced by some other form
of weather.

If a man wants a change of climate, he leaves his
own climate and goes across land or sea to find some-
thing different. If he wants a change of weather, he
has only—at least, in our variable country—to sit still ;
and the change will surely come to him. Every phase
of weather arrives in turn, as eddy after eddy, ripple
after ripple, wave after wave, journey across the
land.

The weather-map, which is true of Europe and the
Atlantic one morning, has often to be quite altered by
the next morning. Nearly all the same eddies may be
still in existence ; but the whole has drifted on, so that
each spot in the map haschanged its weather. Wherea
cyclone was yesterday, a ‘ wedge’ is to-day ; where the
‘wedge’ was yesterday, a big ‘anti’ is pushing its way
to-day; where the ‘anti’ was yesterday, a ‘col’ has
moved to-day; and so on.

People are apt to associate the word ‘cyclone’
with a terrific storm. Yet it does not necessarily mean
a storm, particularly in.temperate regions. A falling
barometer ushers it in; and it does bring some wind
and rain. Whether much or little depends upon what
is called the ‘intensity’ of the cyclone. It may be
languid, or vigorous, or violent; but in each case the
nature of the eddy is the same. The only real dis-
Weather. - 219

tinction ‘between those cyclones which bring a mild
ordinary amount of wind and rain, and‘ those -which
usher in mighty gales with tremendous rain or'snow,
lies in-the ‘ intensity’ of either.* -

The degree of intensity depends upon gohetiee
else. which is rather difficuit. to explain clearly in a
simple sketch of this kind.

A little illustration may help. Suppose you have
to walk up a hill from a level plain. The hill may rise
slowly or sharply. There may be a long or a short
space between the spot where you stand one hundred
feet above the plain, and the spot where you stand
two hundred feet above it.. The long space would
mean a gradual ascent, the short space a sudden ascent.
In either case the hill is said to rise ‘so many feet in
the mile.’

There is a slopef also in a cyclone, not the slope of
a solid hill, but the slope of different barometer-heights.
Where a cyclone exists, the barometer is always lower
inside and always higher outside the eddy. The rise of
the slope, from a lower barometer in one place to a
higher barometer in another place, is reckoned, not
by so many feet in the mile, but by so many tenths
of an inch in the mile.

To illustrate this: suppose you have two barometers,
daily watched, in two towns, three or four miles apart.

One day, the two barometers are the same, the

* The ‘secondary cyclone, the ‘V-shaped depression,’ and the

‘col,’ are, like the cyclone, characterized by falling barometers,
and are known generally as ‘depressions.’ When the. papers speak
of ‘a depression’ coming across the Atlantic, it may be one or
another of these. In any case it probably means some amount of
wind and rain. Occasionally the word ‘disturbance’ is used
instead of ‘depression,’ The anti-cyclone and the ‘wedge’ go

with a high barometer.
+ Called ‘the steepness of the isobars,’:
220 The Ocean of Air.

mercury standing in both at precisely the same height -
This means a calm.

Next day, one barometer is two-tenths of an inch
higher than the other. This means a little wind.

Another day one barometer stands half-an-inch
higher than the other: quite a steep slope. This
means something of a storm.

Yet another day, one barometer stands an inch and
a half or two inches higher than the other: a tre-
mendously sharp ascent. This means a hurricane.

Such violent differences within a few miles are
seldom or never known in the British Isles; but they
are by no means unheard-of in tropical lands.
CHAPTER XXV.
EDDIES OF AIR.

WEATHER foretellings have been popular in all ages;
how popular in this fitful climate of ours is curious,
when one sees how often they fail.

Some signs of rain and fine, believed in from time
immemorial, have a foundation in truth. Unless fairly
often found correct, they would hardly have obtained
such a hold upon people’s minds.

Excessive damp on walls, springing from excessive
moisture in the air, is a most natural token of coming
rain. The red sky and the rainbow of early morning
are about equally ‘the shepherd’s warning.’ Halos
and mock suns, belonging to the van of a cyclone, are
pretty sure indexes of what may be expected. A
hollow luminous circle round the moon may not mean
rain the next day, inevitably, but within two or three
days it is an almost certainty.

The ‘old moon in the arms of the new,’ and
unusual clearness of distant hills, both arising from
unwonted transparency of the air, are marked signs of
rain not far distant. About three mornings of white
frost are held to be equally infallible. Also, birds
and flowers have a voice in the matter. . Swallows
fly low before rain because insects do the same, and
many sensitive blossoms close their petals in anticipa-
222 The Ocean of Air.

tion of a coming downpour. The little red ‘ shepherd’s
glass’ is famous for its true predictions, and a certain
pink starry mesembryanthemum has shown itself
almost equal to a barometer in quick understanding of
the atmosphere.

Signs of fine weather, popularly held, are not fewer
in number. The opposite characteristics of dry sur-
faces, of a hazy horizon, of a crimson sunset, of open-
ing flower-petals, promise fairness. The flying far of
rooks and sea-birds, and the flying high of swallows,
are counted especially hopeful. A white moon pro-
mises well, and so do gossamer webs floating in
abundance.

The difficulty of reading truly all such signs, as
well as the barometer itself, consists in the fact that
the same tokens do not precede all kinds of wet
weather. Before the rain of an ordinary cyclone the
barometer falls, but before another* kind of air-eddy,
which brings rain, the barometer rises.

Besides these uncertainties, one never knows how
long an eddy may last. At any time a cyclone may
die out and vanish.

A storm may be publicly foretold as travelling to
England. Signals may be hoisted, and precautions
taken, and after all it may never appear. It has either
altered its course, going off in a new direction, or it
has quietly broken up and dispersed. The fore-
tellings were correct so far as they went, but the new
freak of the wild air could not be reckoned on.

Now and then a storm strikes our shores, no
warning of-which has been received. This may well
happen, for cyclones travel fast. People often wonder
why swift steamers do not come on from mid-ocean

* The secondary cyclone.
Eddies of Air. | 223

in advance of the storm to tell of its approach. But
the cyclone..which should only keep pace with a
steamer would be a slow, specimen of its kind.

‘There is, of course, the telegraph. If a cyclone
starts from America, instead of taking shape in mid-
ocean, notice can be flashed under the ocean—and a
cyclone cannot compete with electricity. This is how
we often do hear beforehand.

But even an electric message occupies time. Time is
consumed in sending it, in receiving it, in transcribing
it, in despatching it to the central office. Time there
is occupied in examining a great number of telegrams,
in comparing notes, in charting the information re-
ceived, in sending word to British seaside stations.
And all this while the big eddy of air is travelling
rapidly nearer.

The very most thatccan be done generally is to
foretell ‘a cyclone,’ not to say whether it will be mild
or severe.

Various well-known signs belong to the front part
of a cyclone, such as a watery sun and a pallid moon.
High hills and mountains show cloud-caps. Animals
are restless. Neuralgic and rheumatic patients suffer
more than usual. Old soldiers are reminded afresh of
their wounds; corns become troublesome; and irritable
tempers are apt to be upset. The weather is dull
and . oppressive, muggy and cloudy, and more or
less warm rain falls, while the barometer continues to
sink,

Near the centre something of a calm commonly
exists, surrounded by the revolving winds. Patches of
rain, alternating with patches of Blue sky, lie within a
circle of clouds.
224 The Ocean of Air.

When about half the cyclone has drifted by, and
the ‘ trough,’ or the line across of lowest depression, is
past, a change takes place. The barometer begins to
rise. The sky becomes clearer, with woolpack clouds.
The air is more sharp and cold, and the rain, if any
falls, is colder than before.

Acyclone has been described as ‘an extremely com-

plicated vortex, something analogous to an eddy of
water,’ but differing from an eddy of water in that the
latter ‘sucks down,’ while the air-vortex ‘draws upward.’
It has also been spoken of as ‘a huge irregular funnel
of rotating air;’ the winds, whether slight or strong
always revolving round an axis of comparative calm,
spirally like a corkscrew inward and upward. Whether
the vortex of rotating air ever reaches to the upper
limits of the Air-Ocean, or whether it is always confined
to lower regions, seems uncertain. Much obscurity still
exists with neeierencé to its nature.

As a cyclone drifts over a certain place, frequent
changes of wind occur. It cannot be otherwise, since
in no two parts of a cyclone do the winds blow from the
same quarter.

Each cyclone has two distinct motions, not unlike
those of Earth. As the solid body of the earth revolves
upon her axis, so the winds of a cyclone revolve round
its axis. As the whole earth journeys through space,
so the whole cyclone travels across earth:’s surface.

In our part of the world cyclones more commonly
journey from the south-west to the north-east. Now
and then one arrives from the neighbourhood of
Norway; but by farthe greater number come to us from
the Atlantic and from America.

The direction taken by a journeying cyclone is
Eddies of Air. 225

affected by the daily whirl of Earth, much as the direc-
tion of trade winds is affected by it. A cyclone travel-
ling from the north comes to us from the north-east ;
while one travelling from the south comes to us from
the south-west.

Air-circulation within a cyclone is always according
torule. The winds of a northern-hemisphere cyclone
rotate round its axis in a direction contrary to the
hands of a watch: while the winds of a southern-hemi-
sphere cyclone rotate with the watch-hands. By laying
a watch upon a map, face upwards, you may find out
the way of the wind’s rotation in a cyclone.

These rules are reversed in the case of an anti-
cyclone. Here again we have an eddy or vortex of
winds rotating round an axis, though the rotation is
sometimes so languid as to be imperceptible. But the
direction of the winds is exactly the other way from
that of cyclone-winds, being with the watch-hands in
the northern hemisphere, and contrary to the watch-
hands in the southern hemisphere. Moreover, the
spiral movement or the ‘suck’ of an anti-cyclone is
downward, like a water-eddy, instead of upward like a
cyclone. This results ina piling up of the air which
helps to cause a high barometer—one of the signs of
an anti-cyclone.

Anti-cyclones mean generally fine weather, cold in
winter, hot in summer, with hazy distances and little
wind, and commonly with sunshine. On the Continent,
a warm anti-cyclone with a cloudy skyis sometimes seen.

The leading feature of an anti-cyclone is calm, with
what is called ‘radiation weather.’ There is little
cloud or floating moisture to check the quick pouring
out of heat from the ground after sundown. So in

I5
226 The Occan of Air.

an anti-cyclone we have dew or hoar-frost. In large
towns this particular eddy often brings dense fogs.

Persistent anti-cyclones are found both in the far
north and in the tropics—as on the icy plains of
Siberia, and on the burning deserts of Africa,—often
continuing for months unchanged.

Probably an explanation is to be found for the main
distinction between the two eddies, as bringers of rain
and bringers of fair weather, in their opposite modes of
air-currents.

When air rises from below to above—as over the
equator—it commonly has a squeeze from the cold
above, and sends down rain. When air sinks from
higher to lower levels, it can not only hold all the
moisture it held above, but can take in more. So the
rising air of a cyclone would naturally cause wet
weather; and the sinking air of an anti-cyclone would
suck up floating mists, clear the sky, and as a general
rule cause sunshine.

There are rains which cannot be foretold by
‘ weather-curves’ on a map—the rains, for instance,
of the Indian monsoon, of sea squalls, of thunderstorms,
of tornadoes and whirlwinds.

Simple squalls come at sea in sharp gusts, more or
less violent, lasting generally only a few minutes. Two
or three such squalls may be seen at once careering
over the ocean, ruffling its surface. About the most
simple kind of thunderstorm known is such a squall
accompanied by lightning and a clap or two of thunder.

These squalls are merely little local efforts to re-
store the balance of the atmosphere. Thunder-squalls

‘are more common in winter than summer, while heavy
thunderstorms are more common in summer than winter,
Ne

a or ae roe

ae



Wave at Hastings. From a photograph by H. F. Godbold.
Eddies of Air. _ 227

The cyclones which visit the British Isles are tame
«compared with what other countries endure; still, from
time to time we have a sufficiently sharp experience to
learn something about the power of a mighty wind.

Perhaps one of the most fearful ever known to visit
our shores was the ‘ Great Storm’ of November, 1703,
-one year after Queen Anne came tothe throne. France,
Germany, and other countries suffered from it, and over
‘a great part of England the damage done was excessive.
In Kent alone eleven hundred private houses were
-wrecked, and seventeen thousand trees were blown
down. Scores of Churches had their leaden roofs torn
off. Sheep and cattle in countless numbers died, and
many human lives were lost.

The Bishop of Bath and Wells and his wife were
both killed in bed by the falling chimneys of the epis-
‘copal palace. Ely Cathedral suffered cruelly. Of
Brighton Defoe wrote: ‘ Brighthelmstone was most
‘miserably torn in pieces; it made the very picture of
desolation, and looked as if it had been sacked by an
enemy.’

In the Thames no less than five hundred wherries
‘sank ; and the whole mass of vessels—four only of which
escaped—were torn from their mocrings by the violence
of the wind. Twelve men-of-war, large and small,
foundered in different places, and the wrecked remains
-of countless merchantmen strewed our coasts. The
first Eddystone Lighthouse was carried completely
away, leaving a bare reef; and of the men within it,
including the over-confident architect, not a trace could
be afterwards found.

Such scenes as these are happily rare in England,
and the winds, even in their more furious moods, have
often fought on our behalf against foreign foes. No,

I5—2
228 The Ocean of Air.

true Englishman can fail to be thankful for the mighty
gales of 1588, which scattered the Invincible Armada,
swept the Spanish galleons to the far north, and drove
a terrible peril from our shores. Of one hundred and
fifty vessels which left Spain in disdainful pride, pro-
mising triumph to themselves, only fifty-six broken
ships crept back into port. ‘Afflavit Deus et dissipantur.’

The force of rushing air was direfully shown a few
years ago in the Tay Bridge disaster. A ‘terrific gale’
was blowing when the Edinburgh train, quitting the
Fife side, passed on the long narrow railway-bridge
which led across to Dundee. From one hundred and
fifty to two hundred passengers were in the train.
Stormy night though it was, no one thought of real
danger. A few minutes’ quick passage,and they would
reach the other side. The great brick piers and iron
girders were counted strong enough to stand any
ordinary strain.

But men had, as often, miscalculated. Also, no
doubt, the strain was more than ordinary.

The train passed onward upon its slender pathway,
and the passengers within could look down on either
side straight into the wind-tossed moonlit water.
Word was flashed along the wires to the Dundee
station that the train was on its way thither.

Those at Dundee waited and watched expectantly,
mindful of the furious storm. In the moonlit darkness
of a December evening, they could see the train passing
swiftly along the rails. Then suddenly a crash of sound

ould be heard above the howling of the gale, and a
bright flash of fire was seen near the bridge’s centre.
After that—a pause! The telegraph wires refused to
act, and the train could not be seen. Its arrival was
awaited in vain !
Eddies of Air. 229

Madly as the wind hurled itself against aught in its
path, two men made their way along the exposed bridge,
only to find a mighty gap in the structure. So far as
they could see, two or three of the biggest Spans were
swept away; and with them was gone the whole train,
carrying down its entire freight of human beings. Not
one survived that awful plunge to tell the tale.
CHAPTER XXVI.
WHIRLWINDS AND TORNADOES.

AFTER all, the heaviest storms ever seen in England
are but as child’s play, compared with the terrific out-
bursts of tropical lands—the whirlwinds and tornadoes,
the hurricanes, typhoons and pamperos, of countries.
nearer the equator.

A tropical hurricane or cyclone is much smaller in
diameter, and travels much more slowly than the
cyclone of temperate regions; but the whirl of its
eddying winds is far more violent. A cyclone in
Europe will journey at various rates of speed, from
twenty to seventy miles an hour; while a_ tropical
whirlwind seldom moves faster than ten miles an hour.
It is, however, infinitely more destructive, on account
of its greater force of wind.

The two movements of a cyclone may be illustrated
by the two movements of atop. Asa top spins upon
its point, it also travels forward. It may spin fast or
slowly ; and it may travel forward fast or slowly. Each
movement is independent of the other.

Or, again, a man may walk forward, and as he walks
he may whirl round his head a stone tied to a string.
If the whirling stone strikes against anything or any-
body, it maydo somedamage. The amount of damage
depends mainly upon the force and rapidity with which
Whirlwinds and Tornadoes. 231

the stone is whirled; not upon the speed or slowness
of the man’s walk.

So the amount of damage done by wind is in pro-
portion to its violence. The harder it blows, the
heavier are the objects which it can lift and carry
along.*

We are now thinking about the actual motion of atr-
particles. When we talk of a wind blowing at sucha
rate, we mean that the actual substantial particles of
air move thus. When we talk of a cyclone or whirl-
wind travelling over earth's surface at sucha rate, we
mean that the whole great air-wave or atmospheric
eddy travels thus; while in the eddy particles of air
are circling round the central calm at the speed before
mentioned. The crowded particles of air flow in and
out of each eddy; just as particles of moisture flow in
and out of a cloud; just as particles of water flow in
and out of a wave; while eddy, cloud, and wave has
each its individual shape and its motion as a whole.

When a wind blows at the rate of eighty or ninety
miles an hour, the pressure of air is tremendous, and
great damage isdone. Happily wind, even at its worst,
comes more or less in gusts, and bears with varying
weight here and there. A house may be laid low with
a single blast, yet the windows of another house close
by may be unbroken. Such curious freaks in the action
‘of wind are often seen. If it were not so, whole woods
and forests would be levelled, instead of occasional

* Anordinary light or moderate breeze travels from about 12 to 24
miles an hour ; a strong breeze about 30 miles an hour ; a moderate
gale about 4o miles an hour ; ; astrong gale about 50 miles an hour ; ;
a storm about 70 miles an hour; a hurricane about go miles an hour.
How much harder a hurricane can blow it is not possible to say.
When winds reach this degree of fury, neither men nor instruments
are in a state for scientific observation,
232 The Ocean of Air.

trees; and all the chimneys in a town would come down,
where now only a. few stacks are demolished.

Tropical cyclones have usually a patch of blue sky
exactly over the centre, called ‘the eye of the storm.’

- The circular storms of the tropics are known as
hurricanes in the East and West Indies, as tornadoes
and whirlwinds in the United States, as typhoons in
China. The pamperos of South America belong strictly
to the same class, though the term is often used loosely.

Whirlwinds vary in size from the tiny eddies of air,
seen in a street on a gusty day, to the terrific tornadoes
of the States, which bear down everything before them,
and the fearful hurricanes of both East and West
Indies, which leave desolation in their track. Whirl-
winds, whether large or small, probably arise in general
from the meeting of two opposite or nearly opposite
currents of air, the struggle for adjustment causing
naturally an eddy.

The whole history and nature of tropical whirlwinds
are still full of difficulty. Though marked points of
resemblance exist between the hurricane of the tropics
and the more gentle cyclone of temperate regions, the
two are so unlike in many main particulars that it
seems doubtful whether they may be classed together.

Near the coasts of India, hurricanes are most fre-
quent in October and May, when the monsoon-changes
come about. The air has many a fierce struggle then
to regain its lost balance.

In these storms, as in the storms of quieter lands,
there are barometer disturbances, and to a much
greater extent. The ‘slope’ of the barometer-heights
is far sharper.

At the centre of a hurricane the barometer has been
noted as standing fully two inches lower than outside
Whirlwinds and Tornadoes. 233

the storm. This tremendous difference in but a short
distance—for tropical storms are of small extent—must
mean a mighty atmospheric upset, only to be put right
by hurricane-blasts. ;

The word ‘cyclone’* dates from the year 1848.
Until nearly the middle of the present century, the
circular shape of hurricanes was not even suspected..:

Many a good ship has been lost for want of this
knowledge. Caught in a sudden hurricane, it would
battle onward unconsciously towards the centre. There
it would meet with either comparative stillness in the
way of wind, or with violent and changeable gusts,
and in either case with a rough chopping sea. Stillthe
worst of the storm would seem to be over, and the
sailors would be rejoicing in their escape, perhaps
spreading sail more freely—when a fierce roar of
renewed tempest would burst forth from just the
opposite quarter to that which they had before en-
countered. Too often ship and sailors were lost in the
fresh peril.

It will readily be understood how a vessel, crossing
a ciycle of wind, must necessarily meet opposite winds
on the two sides of the circle.

Now that the laws of cyclones are better under-
stood, a captain, finding his vessel overtaken by one,
knows in which direction to steer so as to avoid getting
near the centre, and to escape as fast as possible.

One of the most fearful of modern cyclones was
that of October, 1780, which started from -Barbadoes
and travelled to Bermuda. English ships off St.
Lucia were destroyed, and forty French transports: off
Martinique, carrying four thousand soldiers, were lost,

* From Greek, xixdoe, a circle.
234 - | The Ocean of Air,

simply vanishing with all on board. In Martinique
nine thousand people died, and in St. Pierre not
a house remained standing.. At Port Royal, seven
Churches and fourteen hundred houses, as well as the
Cathedral and the hospital, were all reduced to ruins,
and sixteen hundred sufferers perished in the latter. At
St. Lucia men and animals were lifted up and carried
by the. wind, and a heavy gun was swept thirty yards
from where it stood. Fourteen houses, of the six hun-
dred dwellings in St. Vincent, alone remained when
morning dawned, and not a leaf or twig clung to the
stripped trees in the neighbourhood.*

A Chinese typhoon is much the same as an East or
West Indian hurricane, equally violent and destructive.
One which passed through Canton in August, 1862,
left between eight and nine thousand dead. A gentle-
man living there wrote afterwardT:

‘The gale commenced in Canton to blow with fury
at about eleven o’clock. The river was a fearful sight.
A usually placid stream, no wider than the Thames,
is suddenly converted into a stormy sea, the waves
lashing the shores with angry fury, their dreadful
aspect increased by the dull leaden hue cast on the
clouds and water, and even on the very atmosphere.
Air and water seem completely intermingled and un-
defined. Howling and roaring, they fly past with
impetuous speed, carrying with them thousands of
boats, many of them bottom upward or broken to
atoms by constant collisions, and human beings beyond
the reach of help. . . . Nor are disasters confined to
the river. On shore, houses are constantly falling,

* ©The Atmosphere,’ by C. Flammarion.
+ Letsure Hour, 1862.
Whirlwinds and Tornadoes. 235

and walls tumbling with acrash. Hundréds of families
are in a moment rendered houseless. .

‘The sky is now clearing. The storm has lasted
not quite two hours. It has been blowing from the
north-east. . . . The sun begins to peep out. The
wind subsides as rapidly as it rose... . Not a leaf
stirs. There is a death-like stillness.

‘But what is that? Hark! Ay, and before the
question is answered, more furious than ever blows the
blast from the opposite quarter of the compass. . .
Wreckers afloat and looters ashore are taken by sur-
prise, and many pay for their temerity in their dis-
honest calling with their lives. The same scenes again
occur, and after an hour or two the wind. again, but
more gradually, subsides, and eventually gives place
to fine weather.’

A clearer illustration than this could hardly be
given of the manner in which the whirling eddy of air
passes over a place, bringing in succession most con-
trary winds.

The chief characteristic of the American tornado
seems to be its extraordinary funnel of dark cloud,
formed and held by the revolving winds. Masses of
dust swept up from the earth are mingled with masses
of moisture, making what looks like an upright ‘spout’
of cloud or mud. Where the tornado passes over a
lake or the sea this becomes a veritable ‘ water-spout.’

The spout may be only a few yards in diameter at
its thinnest, widening below and above as it reaches
down to earth and up to the level of low-lying clouds.
The whole area of the storm is often not more than a
few hundred yards across. The entire whirlwind travels
at arate of about thirty miles an hour, or as fast as a
256 . The Ocean of Air.

moderate train. Within that limited space all is de-
struction, the great eddy leaving utter ruin in its track.
Solid buildings are levelled with a single blow, or
‘lifted and turned round before being torn to pieces.’

Such'a tornado took place in May,.187g, ushered:
in, as usual, by close heavy weather. Rain began
to fall, changing rapidly to furious hail. Some of the
stones were found afterwards to be three and a half
inches in diameter, and one at least weighed a quarter
of a pound. The ‘dark inky funnel-shaped cloud’
formed gradually ; a revolving mass of moisture, dust
and mud, upheld by the weight of the revolving hurri-
cane. Its roar could be heard three or four miles off.
Whatever lay in its path was seized, whirled round
and round, and carried onward.

The whole diameter of this storm was only about
forty-three yards, and the’ height of the funnel was
supposed to be about five hundred feet. Asan instance
of the ruin wrought, a huge plough weighing 700
pounds was caught up and borne bodily over a space
of twenty yards. A woman was carried like.a feather
for two hundred yards, then dashed against a wire
fence, not only killed, but stripped of all her clothing,
and deluged with black mud from head to foot. When
the storm had gone by, there came over its desolated:
track a rush of burning air, and then an ice-cold gale
from the north-west.*

We may be thankful that such visitors do not come
to England. Wildly as the winds often howl around
our shores, we have after all to do chiefly with the
milder moods of the Air Ocean.

Our countrymen in other lands, our ships in far-

* Abercromby’s ‘ Weather.’
Whirlwinds and Tornadoes. 237

away ports, come in, as we have already seen, for these
fearful outbursts of atmospheric fury, and a notable
instance took place lately in the Samoan hurricane.*

Some German and American vessels and H.M.S.
Calliope were at anchor in the Bay of Apia, when a
tremendous cyclone burst suddenly upon them. The
waters of the bay were lashed into a fury of waves,
among which the ships were tossed about one against
another, or flung upon beach and reef, helpless to
resist. Some were wrecked, some foundered, and there
seemed no way of escape from the desperate peril.

Two German vessels and one American sloop were
lost, when the Captain of the good ship Calliope came
to a brave resolve. She had already been flung against
the Vandalia, and a collision with the Trenton was near.
Anchors and engines together were failing to save the
American and German ships. But Captain Kane knew
the power of his engines, the spirit of his men. He
determined to slip his cables, to trust to the engines
alone, and to throw the head of his ship into the very
teeth of the hurricane.

This done, there was a brief pause—the powerful
engines at work, the Calliope remaining absolutely at
rest as the winds howled madly past. It must have
been -a pause, however brief, of unutterable suspense,
for upon its outcome hung the fate of the ship, and
probably the life or death of the crew.

Then slowly, slowly, the corvette stirred, moved
onward, and crept by inches at a snail’s pace out of
the fatal bay, away to the safety of the open sea. As
she passed the 7renton a ringing cheer rang out from
the brave Americans, able in their own deadly peril to
appreciate the courageous daring of the English Cap-

* Early in 1889.
238 The Ocean of Air.

tain. One is glad to know that though the Tyventon
was lost, her crew escaped.

The hearty cheer was heartily returned, and the
Calliope was saved. But the powerful engines, or-
dinarily capable of carrying her through the water at a
rate of fifteen knots an hour, were able to make only
about one knot an hour against the fury of that blast.
CHAPTER XXVII.
THUNDER AND LIGHTNING.

OnE of the most wonderful and awe-compelling sights
to be seen in our Ocean of Air, is a brilliant flash of
lightning, with its attendant roar of sound.

Severe cyclones, whether temperate or tropical,
besides bringing fierce winds, heavy rain, and furious
ocean-waves, are usually accompanied by lightning and
thunder. The thunder and lightning of the tropics
are such as we never hear or see in our Island-home.
Yet even in England, death from a lightning-flash is
no unheard-of event.

Indeed, taking them all round, the cyclonic thunder-
storms of temperate climates and of cold seasons, are
really more dangerous than the heat-thunderstorms of
the tropics and of very hot summers. - Though the
lightning may seem less severe, the clouds lie lower
down; and the passage of an electric. spark, not merely
from cloud to cloud, but from a cloud to the earth, is
more common.

Two kinds of lightning are commonly known to us;
Zigzag or Forked Lightning; and Sheet or Summer
Lightning. The second of these is in most cases only
a reflection of the first.

When we look at the flash itself, we call it zigzag
or forked lightning. When we look at the reflection of
240 The Ocean of Air.

that flash on the clouds and in the air, we call it sheet
lightning.

Summer lightning is often the faint reflection from a
storm either too far off, too low down beyond the horizon,
or too high up above intervening clouds, for us to see
the forked flashes themselves. Occasional instances of
summer lightning cannot, however, be thus explained.

There is a curious vagueness in the minds of people
generally as to the duration of a lightning-flash. A
statement was lately made in the leading tale of a well-
known serial, that a certain flash lasted fully ‘half a
minute.’

A flash really lasts no more than the merest fraction
of a second—some say the ten-thousandth, some say
the millionth of a second. None know exactly. No
doubt it seems to continue longer, since the retina of
the eye keeps for a brief space any impression which
falls upon it. This may be shown with the help of
a spinning top. If a piece of paper full of large holes
is made to whirl with the top, it will appear to the eye
like a continuous sheet of paper. The holes in the
paper are, so to speak, filled up by the picture of the
paper between the holes remaining on the retina as the
holes rush by.

So though the actual flash of lightning is over with
almost unimaginable rapidity, its radiance lingers on
the retina of the eye for a much larger part of a second.
But half a minute! never!

The most rapidly moving or whirling bodies ever
seen on earth always appear perfectly still, when seen
by the light of a lightning-flash. This is a sure proof
of its extreme speed.

A good many thunderstorms have already been
described in past pages, under other names. Hail-
Thunder and Lightning. 24

storms, cyclones, tornadoes, hurricanes, severe gales,
even violent snowstorms, are more or less accompanied
by thunder and lightning. From time to time indi-
viduals are struck, and either injured or killed; but
such accidents are comparatively rare.

Some years ago a gentleman and lady were staying
in Wales, not far from Cardigan, when a heavy storm
took place at night. The lightning struck the house,
and the very bed on which they lay was burned: yet
they escaped with their lives. At another time, Derby-
shire being visited by a severe storm, the lightning
struck a certain Grange, passing downwards into a room
where tea was going on. The master of the house was
killed on the spot, while his wife and a servant were
both hurt. But such instances as these. have to be
selected from among thousands of cases where no
material damage is done.

We conie now to the question, What zs a lightning-
flash ?

It is the visible passing of electricity from one cloud
to another, from a cloud to the earth, or from the earth
to a cloud.

And what is Electricity ?

For a long while it was believed to be an extremely
thin fluid, creeping into and flowing through other
substances. Some held that it was a single fluid, acting
in two modes; some that it consisted of two different
fluids.

The idea of electricity being a fluid is now laid
aside. It is believed to be, not a fluid, but one of
Nature’s Forces or forms of energy, acting, in the case
of a thunderstorm, in and through the atmosphere.

We continue, however, to speak of ‘the electric

16
242 The Ocean of Air.

fluid.’ The term is a convenient one, and it has grown
into general use, so as to be not easily given up.

Globular Lightning, so-called, is still much of a
mystery. There can be no doubt about the actual
phenomenon ; but people are apt, when it appears, to
be too much startled and agitated for calm observation.

It takes, usually, the shape of a bright ball of fire,
travelling deliberately through the air, and exploding
with a crash. In size it is said to vary from a few
inches to two or even three feet in diameter.

One such ball was seen in Paris, descending from
the sky; and when it burst, forked flashes seemed to
dart from it. Forked flashes might, however, easily
come from friction, like the excitement of electricity in
the Aurora.

Another was seen in England, rising from the
ground, and zig-zagging upwards, till it passed into a
dark cloud.

A third was seen in Ireland, ‘ floating leisurely’ over
the ground; now and then dipping into the boggy soil,
where each time it dug a deep hole or trench, and at
length burying itself in the earth.

It seems probable that a Fireball partakes rather
of the nature of a meteorite than of a lightning-flash.
If so, it does not come under the head of Electricity,
and the phenomenon altogether is a matter for doubt.
PART VI.

FORCES OF THE AIR-OCEAN,

CHAPTER XXVIII.
ELECTRICITY AND MAGNETISM.

THE whole Earth is full of Electricity, and the entire
Ocean of Air is more or less overflowing with it. But
for the perpetual presence and influence of this Force,
our Atmosphere would be different indeed from what it
isnow. A-chapter may well be given to explaining a
little about Electricity and the twin-power Mag-
netism.

About six hundred years B.C., somebody discovered
that if a piece of amber were rubbed, and were
then held near small scraps of a light substance, it
would attract the scraps, making them spring up and
cling to itself. Before being rubbed, the amber did
nothing of the kind.

jet was proved to possess the same power; and
there discoveries stopped. People were not in those
days very keen after scientific knowledge; or they
would hardly have waited through so many cen-
turies following, through the days of Early Chris-
tianity, and through the Dark Ages, till the time
of Queen Elizabeth, before taking another step
forward.

Though only amber and jet were thus far known to
possess this curious gift of attraction, when rubbed,
the characteristic was found to belong to a great many
246 The Ocean of Air.

substances—to sealing-wax, for instance, to glass,
diamond, sapphire and gutta-percha. Any of these,
if excited by friction and warmth, were seen to at-
tract light bodies, sometimes at a distance of several
inches; and some of them would shine in the dark.
Such substances received the name of ‘electrics,’ at
the beginning of the seventeenth century; while the
mysterious power at work was called ‘electricity.’
The word springs from ‘electron,’ which is the Greek
for ‘amber’

Nothing is easier than in a small way to try this
attractive power for yourself. If you rub a stick of
sealing-wax well with silk or flannel or fur, and hold
the rubbed end near a little heap of very tiny paper-
cuttings, some of the latter will at once spring up, and
cling to the sealing-wax.

Electrified substances do not always attract other
substances. Sometimes they repel or drive them
away. For there are two kinds or forms of Electricity—
Positive and Negative. When a body is electrified, it
is always in one of two different ways.

Try another experiment. Hang a light small ball
of cork by a silk thread; then rub a piece of sealing-
wax, and hold the rubbed or ‘excited’ end near the
ball. At first the ball will be attracted towards the
sealing-wax; but presently it will move away, being
repelled.

The sealing-wax and the cork ball are in the begin-
ning differently electrified—one with Positive, the other
with Negative, Electricity. Then they mutually draw
together—or would do so, if both were equally free to
move. But when each has given over to the other
same of its own Electricity, the two become electrified
alike; therefore each drives the other away, and they
Electricity and Magnetism. 247

fly apart—or would do so, if equally free. The ball
alone being free, alone moves.

So if one body electrified with Positive Electricity
comes near another body electrified with Negative Elec-
tricity, each attracts the other, and if free to move
they draw closer together. It seemsasif the electricity
of the one desired to flow into and mix itself with the
electricity of the other. But when two bodies are near
together, both electrified with Positive or both with
Negative Electricity, no such desire is shown. On
the contrary, each seems anxious to get away from
the other.

If electricity were a fluid like water, we should say
that it flowed from one substance to another, in the
struggle to keep its own level. If electricity were a
fluid like air, we should say that it flowed to and fro
in the struggle to keep its balance or equilibrium.
Since it is neither, those terms are perhaps hardly
allowable. Yet there is in electricity, as in the
said fluids, an incessant effort after something like
balance, after something like equality, after a perfect
adjustment and a fair distribution of itself every-
where.*

Although Electricity cannot be considered a fluid,
it behaves in many respects very like a fluid. It is
indeed caused to appear, or ‘ generated,’ by rubbing,t
which is not the case with any known fluid; but
* generated’ does not necessarily mean ‘made.’ Elec-

* This constant flow of electricity from one body to another is
said to be caused by ‘a difference of potential,’ which really means
a difference of level or balance or of intensity of electrical condition.

t+ Itis also generated by pressure, by heat, by chemical action.
etc.
248 : The Ocean of Air.

tricity seems to be in all bodies, hidden away, only not
apparent to us till its quiet is disturbed by friction or
other causes.

The manner in which it flows from one to another
part of a substance, or from one body into another,
is very like the action of a fluid.

Again there seem to be definite quantities of it
everywhere. Electricity cannot spread and increase
like flame.. When some flows out of a body, less
remains behind. Every time one substance rubs or
even touches another, a flow of electricity takes place,
one way, if not both ways; though without exhibiting
what is called ‘electrical action.’ So-the quantity
present in any one body is always varying.

But here we come upon a marked difference between
different substances. Some show electrical action
much more easily than others. You have seen how
sealing-wax, when rubbed, immediately attracts or
repels: and it is the same with all so-called ‘ electrics.’

Many substances, such as gold and silver, marble
and pearl, iron, and indeed all metals, may be held in
the hand and rubbed to any extent, without producing
the same result. In past days they used to be called
‘non-electrics,’ because, it was supposed, they could
not be electrified.

Now that term is dropped; for when a ‘non-electric,’
such as silver, is rubbed, we know that electricity is
generated just as fast as when an ‘electric,’ such as
sealing-wax, is rubbed. The difference consists, not in
the amount of electricity, but in the ease with which
the metal conducts it away, compared with the resis-
tance offered by the sealing-wax. So now we talk, not
of ‘electrics’ and ‘non-electrics,’ but of ‘ good conduc-
tors’ and ‘bad conductors.’
Electricity and Magnetism. 249

Iron is a good conductor, and so is the human body.
If you hold a lump of iron in your hand, and rub as
hard as you will, you cannot make it attract or repel.
For just so fast as the electricity is generated, it pours
away into your hand, up your arm, and down your body
into the ground.

But suppose you fasten the lump of iron upon a glass
support, and do not touch it with your hand. Glass
being a bad conductor, communication with the ground
is thus cut off. If the iron now be rubbed, it will
attract and repel like excited sealing-wax.*

There is still, however, a difference between the iron
and the sealing-wax. When a stick of sealing-wax is
electrified by rubbing, all the electricity remains or
seems to remain on the outside, just where-it has been
generated. It does not flow around and along the
stick to other parts. When the iron is electrified,
being cut off from the ground by a glass support, the
electricity flows freely over its whole surface, though
unable to get any farther.

In both these cases the store of electricity on:the
surfacef is spoken of as ‘a charge,’ and the iron or
sealing-wax is said to be ‘charged.’ If the stored-up
electricity passes away from either, it is then said to
be ‘discharged.’ But when the electric stream flows

* When: a good -conductor is cut off. from the earth and other
good conductors, by a bad conductor like glass being placed be-
tween itand them, it is said to be ‘insulated,’ or put upon an island.
Bad conductors are also called ‘insulators.’

t+ Whether electricity always is, as it appears to be, only on
the outer surface of conductors cannot be declared with certainty.
There may be electrical excitement in ‘the interior, though electrical
action shows itself on the outside alone.

A gas or vapour cannot be charged, like a solid or liquid, on
the outer surface only, since it can hardly be said to have an outer
surface. :
250 . The Ocean of Air.

freely along a good conductor—as for instance along a
wire—it is characterized as ‘an electric current.’

Now water is a good conductor. An electric wire
laid under the ocean has to be carefully guarded from
contact with the surrounding water, or the electric
message, flashed from one country to another, would
all leak away into the ocean by the way.

Dry air, at least in the lower regions of the Air-
Ocean, is a bad conductor. If it were not so, no ‘ good
conductor’ could ever be electrified by being fastened
upon a ‘bad conductor,’ because even though cut off
from earth and other substances, it would still be
touched on all sides by air, and all its electricity would
flow away into the atmosphere. Dry air acts in some
degree like the glass support, and imprisons the

‘electricity.

Floating vapour in the air, however, helps to give
‘right of way’ to electric currents, and prevents
air from being a thoroughly bad conductor. In very
damp weather, air becomes a much better conductor,
and on such days electrical experiments are apt to
prove a failure, because of the quick passing away of
electricity into the vapour-laden air.

The damper air is, the better it conducts. On the
other hand, the denser air is, the worse it conducts.
Both these facts tell upon the lower layers of the Air-
Ocean, which are alike more damp and more dense
than high layers. Air may be said to act generally as
an insulator or bad conductor; but only to a certain
extent. If an excited stick of sealing-wax or glass is
left in the open air, it gradually loses its little ‘ charge.’
The store of electricity on its surface leaks away into
the air, faster or more slowly according to whether the
atmosphere is damp or dry.
Electricity and Magnetism. 251

When two clouds draw near together, one charged
with positive and the other with negative electricity,
there is a strong attraction between the two. In
either cloud the electric streams flow, converging,
towards one part, that part of the cloud which lies
nearest to the other cloud.

Sometimes the state of the atmosphere will allow
a quiet and gentle restoration of electrical balance.
If, where the clouds lie, the air is damp enough, and
not too dense, a current may make its way from one
cloud to the other, without anybody on earth being
aware of it.

But if the air is very dry, it resolutely resists the
passage of the current. Things go on getting worse
and worse, till at length they have to be righted, not-
withstanding all opposition. If the electric current
may not flow peacefully, it will end by forcing its way
fiercely. Then the culmination comes. An enormous
spark of electricity leaps from cloud to cloud with a
crackling roar.

Thunder, as we hear it, comes to us commonly
softened in some degree by distance, and lengthened
out by rolling echoes. Sometimes, when a storm
takes place close overhead, we hear for once the
actual metallic crash, unsoftened.

An electric spark, caused to pass from point to
point of an electric machine, leaping through only an
inch or two of space, will make a noise, by no means
contemptible. No wonder the great lightning spark,
rushing through miles of space—sometimes as muchas
eight or ten miles—should shake the very earth with its
peal.

The sound is caused by the electric current forcing
its way through the fiercely-opposing air. In the
252 The Ocean of Air.

struggle it-turns to and fro, following a zigzag path.
Like a river, it flows where it finds least resistance. ~

When an electric current passes through a resisting
substance, there is always great consequent heat.. The
air, under sudden and tremendous heat, expands in-
stantaneously to an enormous extent, and contracts
again as rapidly the moment the flash has gone by.
An immense rush and pressure of air-particles are thus
caused. The crackling thunder-crash is the fruit of
the furious air-resistance, air-expansion, and air-con-
traction.*

A lightning-flash travels at the rate of about
290,000 miles in a second: half as fast again as the
speed of light.

Lightning-conductors are often placed near high
buildings. The object is to offer a safe and easy path
to the electric-current, from the clouds into the earth,
—safe as regards mankind, easy as regards the light-
ning. Electricity will always take the easiest path
which offers itself. A ‘conductor’ is made of metal,
which allows free flow to the current. It ought to end
in a damp layer of earth, where the current can spread
itself about harmlessly.

One can hardiy speak of lightning-conductors with-
out an allusion to Dr. Benjamin Franklin, of Phila-
delphia, to whose experiments the world still owes
much. He it was who, about 1750, first sent a kite
aloft during a-thunderstorm, rightly calculating that
electricity from the charged clouds would pass down the
string. A key was tied to the latter within his reach:

* A discharge of electricity through a non-conductor—such as
the lightning-spark passing through-air—is called ‘a disruptive dis-

charge.’ - Such a discharge is usually accompanied by light, heat,
noise, etc.
Electricity and Magnetism. 253

and when he touched the key: with his knuckles. he
drew from it a bright electric spark.

Such experiments meant, and must always mean, no
little danger to the experimenter.. Franklin escaped
unhurt; but others have been less fortunate.

About the middle of the 18th century a melancholy
event took place. Professor Rechman, of St. Peters-
burg, had put up on his house an iron rod to collect
the electricity of storms ; and he had below an electro-
meter to measure the amount collected. One day,
during a severe storm he was carefully watching the
electrometer, bending his head to about a foot distant
from it, when a loud peal of thunder sounded. In-
stantly a bluish ball of fire, as large as a man’s fist,
leaped from the iron rod to the Professor's head, ‘ with
a report like that of a pistol.’ Rechman fell dead: and
his half-stunned companion was. covered with red-hot
bits of metal wire.

Electricity and Magnetism are commonly spoken of
together. They are, in many respects, alike; yet the
two are not the same.

The lodestone was known in early days as a magnet,
having a power of attracting to itself filings of iron or
steel. Butits singular characteristic of always pointing
north and south, when so suspended as to have free
movement, was not found out till about the eleventh
century.

If iron or steel are rubbed on a lodestone they gain
the same powers. Magnets to any extent can thus
be manufactured.

Attraction and Repulsion are connected no less with
Magnetism than with Electricity.

There seem to be two kinds of magnetism, or, at
254 The Ocean of Air.

least, two kinds of magnetic poles. A magnet has
always two poles, each different from the other. Ifa
magnet is broken in half, each half at once has its
two different poles.. No one magnet has ever two poles
of the same kind. The one pole attracts what the
other repels. The one points only north, and the
other points only south.

Take a magnet, and hold each ‘pole’ of it in turn
near the north-pointing end of the needle in a com-
pass; then do the same with the south-pointing end.
You will find that one pole of the magnet attracts,
while the other repels, the north-pointing needle.
But with the south-pointing needle you will find the
reverse. It is attracted by that pole of the magnet
which repelled the north needle-end, and repelled by
that pole which attracted the north needle-end.

In fact, the rule here is much the same as in elec-
trical attraction and repulsion. Magnetic poles, when
alike in kind, repel one another; when unlike in kind
they attract one another.

All this is very curious, very easy to see and test
for ourselves, and by no means easy to undevstand.
There is a great deal in magnetism which nobody does
understand as yet.

One clue to further researches has been obtained
of late years. This is, that the Earth itself is a huge
Magnet, with North and South Magnetic Poles, not
far from the North and South Poles of geography.

Probably also the Sun is another and most enor-
mous Magnet.. It may be that a clue lies here for the
future, as to the real nature of the mighty Force
Gravitation.

Iron is more easily ‘ magnetized,’ by rubbing witha
lodestone, than steel, and as a natural consequence it
E lectricity and Magnetism, 255

is also more easily demagnetized. As a writer says*:
“It is harder to get the magnetism into steel than into
iron, and it is harder to get the magnetism out of steel
than out of iron, for the steel retains the magnetism
once put into it.’

Just what one would expect! As we saw in the
case of water and solid ground gaining and parting
with heat; that which is most easily taken in is also
most easily lost, and vice versd.

The attracting and repelling powers of a magnet
will act through paper or wood, through glass or brass,
through fire or water, but not through a screen of iron
or steel. The iron and steel themselves attract the
magnet, and so interfere with its powers over anything
beyond them.

For a long while the fluid-theory was used to
explain magnetism. That theory is now given up.
Whatever magnetism may be, a fluid it is not. The
term is still employed, but merely as a convenience.
Magnetism, like Electricity, is held to be one of
Nature’s Forces, not in any sense one of Nature’s
Substances.*f

Side by side with the marked resemblances between
these twin-forces there are marked differences ; such,
for instance, as the following. When electricity passes
from one body into another, a certain amount of the
‘fluid’ is gone, and less remains behind. But when a
magnet is rubbed on a lump of iron, magnetism passes
into the iron, and apparently just as much remains
behind in the magnet as was there before.

* Thompson.

+ It is now believed that Electricity is of the nature of waves:
not waves of air, like sound, but waves of ether, like light.
Magnetism may also come under the same category.
256 The Ocean of Air.

A bar of iron or steel may be magnetized. through
being touched or rubbed by a lodestone or.a steel
magnet. This, however, is not the only mode.. If no
lesser ‘permanent magnets’ are at hand, the biggest
magnet of all within reach, the Earth itself, may be
used. An iron bar placed upright for a long enough
period gains magnetism out of the earth. . Moreover,
heating and cooling under certain conditions may
have the same effect. A steel bar, made red-hot, then
allowed to cool, while lying nearly north and south, or
in the ‘magnetic meridian,’ is found to be magnetized.
If it lie east and west, it is not magnetized.

A more vigorous mode of magnetizing than any
of the above is through a powerful current of
electricity, borne continuously by spiral wires round
iron or steel bars. Here again we see the close con-
nection of the twin-forces, a stream of electricity being
actually converted into, or being at least the direct
cause of, magnetism. This magneto-electric union
has been carried out to a wonderful extent, with mar-
vellous results, in the electric-lighting. machines of our
days.

Passing mention must be made of the Aurora
Borealis, a glimpse of which is sometimes vouchsafed
to us so far south as in England, though it is in the icy
regions of the north that the sight is seen in all its
splendour.

A certain observer belonging to a scientific expedi-
tion describes some of the wonderful and rapid changes
noted in a single display. Rays of brilliant white shot
over the firmament, lengthening, then dying out, to be
followed by another spreading group of fan-like rays.
Then golden waving draperies seemed to-float and fold
Electricity and Magnetism. 257

one over another. An arc of deep red contrasted with
a ‘segment’ of black, and a shining fan widened
through the northern sky, rising gently upward. Over-
head its rays joined into the shape of a crown, and
from the crown sprang radiant jets of light and colour.
Blue and green, yellow and red, quivering streamers of
every hue, helped to turn the sky into a ‘cupola of
fire’; and presently the whole faded quietly, leaving
only the stars twinkling in the dark night.

The light of a bright aurora is so clear that small
print has been read by it. The height of the aurora
rays is believed to be from about thirty to over one
hundred miles above earth’s surface.

The aurora is, there can be little doubt, in some
measure due to electrical and magnetic forces. It is
generally accompanied by magnetic storms or dis-
turbance, shown by magnetic needles. Moreover, a
singular connection has been observed between the
periodical increase in auroral activity—shown by its
appearance farther south—and the periodical increase
of sun-spots ; which again has a remarkable connection
with certain periodical oscillations of the magnetic
needle.*

A new theory has, however, lately sprung into exist-
ence, which may help to account for the northern
display.

Higher levels of the Air-Ocean are believed to be
filled with ‘interminable clouds of meteoric dust ’;+
that is, of the material of which meteorites are made,
floating as extremely fine dust. These clouds of dust
incessantly receive fresh additions, as day by day
millions of meteorites enter our Atmosphere from the
vast Beyond; and there must be also an incessant

* See ‘ Sun, Moon and Stars,’ p. 131. t Dr. Pritchard.
17
258 : The Ocean of Air.

tendency of the dust to descend, however slowly,
earthward.

If this be so, one would expect to find traces ot
meteoric dust upon Earth’s surface or in the sea. It
is a remarkable and suggestive fact that, in the Challenger
expedition, dust-grains or ‘nodules’ were dredged up
from the Ocean-bottom, having every appearance of
‘meteoric origin.’ The searching test of the spectro-
scope* showed this dust to be one in nature with the
dust which enters our Atmosphere from distant space ;
and the same test, applied to the light of the Aurora,
revealed that the spectrum of the Aurora and the
spectrum of Meteoric dust are in a measure the same.t

It is now thought by some that the auroral display
is—at least to some extent—due to abundant supplies
of dust, including Meteoric dust, in the upper Air-levels;
such dust being in particular circumstances ignited by
friction with the Air, or acted upon by electricity.
How far the electricity is generated by the said friction
is another question.

* See ‘Sun, Moon and Stars,’ pp. 79 and 290. /

+ According to Professor Lockyer and others, sone of the
nedules, dredged up from the deepest waters of the oct:an, contain
manganese ina form which suggests the higher parts of our Atmos-
phere as their probable origin. There, undoubtedly, manganese
‘dust plays its part in the phenomena of the Aurora Borealis,
CHAPTER XXIxX.
HEAT.

Mucu has been said from time to time about the part
played in the Ocean of Air by Heat. A few pages
about Heat and its modes of action may not be un-
interesting.

When we speak of a thing being hot or cold, we
mean hot or cold as compared with something else,
generally with the surrounding atmosphere. That
which one person calls hot another calls cold; and
what seems hot to us at one time seems cold at
another. It is all a question of comparison.

The true temperature of a body can only be known
by the thermometer, not through touch. The hand
can merely feel that a substance is more or less warm
than itself. Since a hand is always changing its own
degree of warmth, it can be no fair standard for
measuring the warmth of other bodies.

Some substances gain and lose their heat much
more readily than some others.

Iron takes in and gives out heat faster than wood.
If you have a lump of warm iron, and a piece of warm
wood, both just the same in degree, the iron will feel
hotter to your hand. It gives over heat to your hand
more quickly than the wood does. But if the iron
and wood are both cold, still alike in degree, the iron

I17—2
260 The Ocean of Airs

wil! be coldest to your hand. It takes in heat, robbing
your hand for the purpose, more quickly than the
wood.

Not long ago Heat was believed to be a sort of very
thin fluid—the pet fluid-theory again !—far thinner and
more delicate than air. This fluid, commonly called
Caloric, was supposed to flow through the tiny inter-
stices of solids and liquids, and among the floating
particles of air or gas, passing freely from one body to
another.

The notion of Heat beirg a fluid, or any kind of
substance, is now entirely given up. Like Gravitation,
like Electricity and Magnetism, Heat is believed to be
a Force, or Form of Energy.

- . A ‘Force’ has been described as that which chanyes
the form or the place of a body. The said ‘body’ may be
of any imaginable kind or size, from an invisible
particle of air, a speck of dust, or an animalcule, to
an elephant, a mountain, an ocean, a world, or a sun.

Heat certainly does so much. It makes bodies
grow bigger. It transforms solids into liquids, and
liquids into gases. It alters the very nature of sub-
stances, turning one kind into another kind. It keeps
up incessant motion of bodies and substances in the
Ocean of Air.

Not that Heat alone could do all this. But Heat
does not work alone. No ‘single Force of Nature
works alone. All the Forces toil together, inter-
changeably, resisting and» yet helping one another.
The Force of Heat works with the Force of Gravita-
tion, to bring about the great Circulations of Air and
Water, and the Forces of Magnetism and Electricity
have a share in the task.

When heat passes into a body, it does not always
Heat. 261

remain there as heat. Sometimes it is transformed
into some other form of energy or working-power,
which again can be transformed to heat. This inter-
changeableness of the Forces of Nature is very curious
and interesting, though too complex a subject to be
more than alluded to here.

A cannon-ball is sent flying through the air, by a
mighty and sudden expenditure of heat. The heat
disappears, being transformed into rapid motion. The
ball is then brought to a sudden standstill, by a strong
stone wall, which it cannot break through. Thereupon
the motion vanishes, and heat, so to speak, reappears;
great heat being given out at the moment of the ball’s
concussion with the wall.

Another example is found in the steam-engine.
Heat there goes in as heat, but it comes out in the
form of work,—the work done by the engine, in draw-
ing a heavy train. If the engine is stopped suddenly
by a collision, motion ceases, and heat is given forth
instead.

Even in so smalla matter as rubbing two dry sticks
together, to gain a few sparks of fire, you have once
more an instance of Work or Motion transformed into
Heat.

One thing that Heat is always trying to do, is much
the same as Air and Water and Electricity are always
trying to. do. It is perpetually striving after a com-
plete equilibrium. It is ever seeking to distribute itself
about, everywhere alike. Heat is incessantly flowing
from one object to another, from hotter bodies to
colder bodies, that the temperature of all bodies may
be the same.

Heat passes from hotter to colder bodies, and pro-
262 The Ocean of Air.

bably also in a less degree from colder to hotter bodies.
Each body which has any heat gives forth of that heat,
not because some other body needs more, but simply
because, being hot, it must radiate or pour out heat all
round. .

Yet undoubtedly the more abundant. flow is from
the warm to the cold surface; for the general ten-
dency is always towards an equalizing of the tempera-
tures of objects near together. Ifa body receives more
heat than it gives off, it grows hotter; if less, it grows
colder; if exactly the same amount, it grows. neither
hotter nor colder.

Heat, therefore, is something which can pass from
one object to another. Not only so: but, as with
electricity, the quantity which passes is a measurable |
quantity, and when a certain amount has been given
off, less remains behind.

Heat flows continually from solids and liquids into
the air, also from the air into solids and liquids.

On a very cold day, a man’s body being much
warmer than the atmosphere, a rapid stream of heat
pours from his skin into surrounding air-particles,
leaving his skin the colder.

On a very hot day, if he goes out from a cool
shelter into a blaze of heat, his skin is the coolest.
Then a stream of heat passes from surrounding air-
particles into his skin, giving a sensation of warmth.

Heat entering any substance causes that substance
to grow larger, by driving the particles further apart.
Heat leaving a substance causes that substance to
grow smaller, by allowing the particles to draw nearer
together. This has been gone into earlier. The with-
drawal of heat makes a gas shrink into a. liquid, and
a liquid into a solid.


A Frozen Torrent. From a photograph by the Rev. F. W. Stow.
Heat. 263

There are liquids which actually take up more
space in the act of freezing than before, such as water *
and molten iron. This is only a.matter of crystalline
arrangement. The actual particles are always closer
ina solid than in a liquid; but as the substance crystal-
lizes according to the law of its being, the ice or iron
needles lie across and among one another in such a
way as to leave empty spaces between; and thus the
frozen substance fills a larger space than the liquid did.

The broken water-pipes of a severe winter are en-
tirely due to this fact. They break, not when the thaw
begins, but when the frost first comes. The water in
the pipes freezing and crystallizing occupies increased
room: and not even strong iron can stand against the
sudden and tremendous pressure of the little delicate
ice-needles. But the breakage is not discovered until
the ice melts, and pours into the house as water.

An experiment has been often tried with small iron
bottles, the iron being half-an-inch thick. Such a
bottle is filled with water, is tightly closed, and is
placed in cold sufficient to freeze the water. Gradually
the water does freeze; and presently more room is re-
quired by the newly-forming ice-needles. Half-an.
inch of solid iron cannot stand against that pressure.
A sound of breakage is heard. The thick iron is
shivered by the imprisoned forces.

This same irresistible power is seen in steam-
particles. Water commonly boils, passing away as
steam, at 212° F. On a high mountain, where the
weight of the atmosphere above is less than at the sea-
level, and where consequently there is less air-resistance
to the flying apart of the water-particles, it boils with a
smaller amount of heat. Each separate kind ef liquid

* See page 116.
264 The Ocean of Air.

has its own especial boiling-temperature, one needing
more heat, another less.

If a liquid is changed into a gas by boiling, the
gas or vapour takes up enormously more room than
the liquid did. Heat drives the particles furiously
apart. The steam froma kettle of boiling water fills
about seventeen hundred times as much space as the
water in the kettle. Repulsion among the steam-
particles is a mighty power for work, as we well know
in the present day, and a mighty power also for danger
to life and limb, as seen in boiler-explosions. If the
steam-particles have not room to rush far enough apart
in their fierce mutual aversion, they will burst through
strong iron, stone, brickwork—anything rather than
be compelled to keep closer company. They will not
gently and calmly force a way like the ice-needles,
but will burst madly free, dealing damage on all
sides.

Heat acts much more powerfully upon some sub-
stances than upon others. In other words, more heat is
needed to raise their temperatures.

Suppose you have a pound of lead, a pound of iron,
and a pound of water; and you want to make each
four degrees hotter than it is now. It will take more
than three times as much heat to do so with the iron
as with the lead; and a great deal more heat still with
the water.

Or, to put the matter otherwise: suppose a certain
quantity of heat is allowed to pass into each of the three.
The lead will then become hotter than the iron, and the
iron than the water.*

* This difference is spoken of as the ‘specific heat’ or the
capacity for heat’ of each.
Heat. 265

Now the fact is, all heat passing into a body or
a substance does a definite amount of work there.
But the work is not all of one kind. Part consists in
iriternal changes among the particles of the lead, iron,
or water; and this is not apparent to our senses. Part
consists in raising the temperature of the lead, iron
or water as a whole; and this is apparent to our
senses.

With some substances there is more internal work
to be done before the temperature can be raised; and
so more heat goes to the first, less remains for the
second. Or, as it has been expressed, ‘ Different bodies
give heat different degrees of trouble, if I may use the
term, in shifting their atoms and putting them in new
places.’** With water, more heat is necessary for the
hidden operations than in iron; therefore under the
same amount of heat water does not become so warm
as iron does. Conversely, when they are growing
colder, the water has or gives more ‘ trouble’ in part-
ing with its heat, so it 8rows cold more slowly. 7

When a body passes from the solid to the liquid or
from the liquid to the gaseous form, the same is seen
more markedly. If you want to convert a lump of ice
at 32° F. into water, a large amount of heat must pass
into the ice, and that heat will simply vanish. It will
all be converted into motion and change among the
ice-particles. When the ice has become water, the
water is not a whit warmer than the ice was. Again,
if you have boiling water, just ready to pass into steam,
far more heat is needed to work the change than was
required even to transform the ice into water; yet,
when it is done, the steam will be precisely the same in
temperature as the boiling water was. All the heat

* Tyndall.
266 , the Ocean of Air.

will have been used up in the internal changes among
the water-particles.

Condensing of steam into water, and freezing of
water into ice, means simply a reversal of the above.
Heat then is given out, instead of being taken in.

Heat is diffused or spread about in three different
modes.

First: it passes or is conducted from one portion to
another of a body. Ifa silver spoon is placed in a cup
of hot tea, the warmth spreads upwards through the
spoon, being handed on from particle to particle, till
the end of the handle is hot. Silver is a ‘good con-
ductor’ of heat.* If a bone spoon is used, the handle
will remain cool, since bone is not a good conductor.
The heat does literally spread in both cases, but the
conduction in bone is so slow that the heat which finds
its way along passes off into the air. It is stolen on
the road by air-particles, and so does not reach the
handle-end.

Secondly: it is conveyed by the movement of a
warm body from one place to another. Our British
Isles have their moderate temperature, through
tropical heat being carried northward by the Gulf
Stream, and given over to us.

Thirdly: it is borne by the passage of heat-rays
from one body to another body at a distance, through
something lying between, which does not itself inter-
cept or stop the rays.

For instance, the heat-rays cf the sun pass through
the Ocean of Air, parting with only a small proportion

* Paper is a very bad conductor of heat ; consequently it makes
a good covering fora cold night, when blankets are lacking. The

poor who sleep « out in Trafalgar Square are often seen to use news-
papers for coverlets.
Heat. 267

of their heat by the way,* and falling upon the earth.
The air alone has a very limited power of stopping
the rays: and it is only when they are stopped, only
when they are taken captive, that they have a heating
effect. Moisture floating in the Atmosphere has con-
siderable power to capture and use the heat-rays, but
dry air has almost none.

Heat coming from the sun is called ‘ radiant,’
because it travels in rays, always journeying straight
onward. A sun-ray may be diffused or spread about
by the air, its light being reflected from one particle to
another; and it also rebounds from a solid surface ;
but in itself a ray never bends, never curves.

Other objects beside the sun pour forth rays of
heat and light. Every heated substance sends out
such rays. Whether or no the rays are visible to us
depends upon whether our eyes are able to see them.
Human eyesight has only a certain range.

When a body is too cold for us to feel any warmth
at all coming from it, a very delicate thermometer
will show that radiation of heat is going on. Rays
are given off, which, if our skin were sensitive enough
we might feel, if our eyes were sensitive enough we
might see.

When a body is a certain number of degrees warmer,
we are aware of the heat-rays, not by sight but by sen-
sation. That comes first. Put your hand near a boil-
ing kettle, and you are conscious of the heat radiated
forth by the kettle. Those heat-rays, though invisible
to the eye, might be visible if the retina of the human
eye were more sensitive. Every heat-ray is also a light-

* Any substance which, like air, allows free passage to rays of
heat, is called dathermaneus. Any substance which will not do
so. is called athermunous. :
268 The Ocean of Air.

ray; but the light is pitched too low for our sight.
A certain kind of paper, however, prepared in a par-
ticular way, is sensitive to those rays. The photo-
graph* of a boiling kettle in the dark—that is to say,
in what we count to be darkness—has been taken on
such paper by the means of its own light-rays, invisible
to our eyes.

When a body is so much warmer as to become
red-hot, we see something of its light, though only as a
dull glow.

When a body becomes white-hot, it begins to give
forth those brighter rays which we usually describe as
‘ shining.’

It is a curious fact that heat-rays, coming from an

extremely hot body, like the sun, can dart through a
substance which would stop or weaken the rays from
a body only slightly heated.
__ Asheet of glass has no effect whatever in stopping
the sun’s bright rays. But it has a marked effect, if
used as a screen, in checking the duller heat-rays from
the drawing-room fire.

The atmosphere, unless when very damp, has an
extremely limited power to stop the sun’s bright rays.
But when those rays have heated the ground, and the
ground in its turn radiates heat, the air has a very con-
siderable power to stop the duller rays of so-called
‘dark heat ’—dark to our eyes only !—poured forth by
the ground.

A conservatory is made on the principle of ‘ bright’
and ‘dark’ heat-rays. The rays coming straight from
the sun pass through the glass, and heat the interior.
But the rays coming from the heated floor and other
substances within cannot pass through the glass, and

* Dr. Huggins.
Heat. 269

are kept imprisoned. Thus the place grows hotter and
hotter.

We are able to see just so much and so many of
the heat-rays, which stream from all substances having
any degree of warmth, as our eyes are fitted to see.
Only that, and no more. Our eyes are formed to
receive and to use certain rays, not the lowest or the
highest in the whole scale of Heat and Light.* Wonder-
ful as it is to think how much we are able to see in the
Universe, there is something more wonderful still—
and that is, how much goes on which we are not able
to see !

One writert+ says: ‘It does not appear that any body
can be so cold as not to send forth radiations.’ Mark
this :—not any body existing! ‘The reason why all
bodies do not appear to shine, is that our eyes are
sensitive only to particular kinds of rays, and we only
see by means of rays of those kinds, coming from some
very hot body.’

Had we but eyes to see, what a world of radiance
we should find around! All objects that now are dull
and plain would shine with unceasing brightness! All
that means darkness to us now would then be only
varying notes, higher or lower, in the scale of universal
Light !

* ©The belief now universally prevalent is that the rays of heat
differ from the rays of light, simply as one colour differs from
another. As the waves which produce red are longer than those
which produce yellow, so the waves which produce this obscure
heat are longer than those which produce red. In fact, it may be
shown that the longest waves never reach the retina at all ; they
are completely absorbed by the humours of the eye.... I have
spoken so far of obscure rays only ; but the selfsame ray may excite

both light and heat.’—Tyndall’s ‘Glaciers of the Alps,’
T Maxwell.
CHAPTER XXX.
SOUND AND LIGHT.

WitHout Heat the Ocean of Air would be a frozen
mass of solid substance. Without Light the dwellers
in that Ocean would be plunged into the depths of a
perpetual midnight. The rays of heat and light, ever
darting down from the great Sun, quiver and palpitate
through the Atmosphere, bringing warmth and bright-
ness to creatures living below.

But what are heat-rays and light-rays? What are
‘rays,’ used in any such sense ?

This is a difficult subject, hardly to be treated in a
few pages, yet not to be entirely passed over.

We know comparatively little as yet about the
nature of heat, and not more about the nature of light.

Many different explanations have been offered at
different times, to account for the passage of heat and
light from sun to earth. None perhaps have been
altogether satisfactory; certainly none can be looked
upon as a final stetlement of the question. At the
present moment the most widely-accepted theory, and
that which, so far as it goes, fits in best with what is
known of heat and light, is the Wave explanation.

Waves of many kinds are known to us; notably
sound-waves in Air. Sound, as the term is commonly
understood, could not exist without Air to carry it.
Sound and Light. 271

The rate at which sound travels through the air, is
about one mile in five seconds. Not nearly so fast as
light and electricity travel, yet about ten times as fast as
the most rapid of hurricanes.

Everybody knows, or ought to know, that sound
takes time to make a journey. The commonest obser-
vation shows so much.

If we watch rock-blasting at a distance, the flash and
puff of smoke come first, then after a slight pause the
noise of the explosion arrives. Ina thunderstorm the
lightning flash is seen first, and, unless the storm is close
overhead, there is a little break before the peal begins.
Five seconds’ pause shows that the storm is a mile
distant, ten seconds’ pause that it is two miles distant.

During the pause or break, the sound is travelling
towards us from the starting-point, and not only
towards us, but outward in all directions. In fact,
it radiates forth, much as heat and light do, only we do
not commonly use the word ‘ radiation’ for sound.

Any solid substance coming between hinders sound.
You may have heard, when listening to Church-bells as
you walked along a road, how at one particular point
the sound was suddenly cut off, either lessened or made
to cease. A high stone wall had intervened, and the
waves of air were turned in another direction.

If you had found your way to the right position,
you could have heard those same waves of air rebound-
ing from the wall, and you would have called the
reflected sound ‘ an echo.’

For sound is conveyed by Waves; sometimes de-
scribed as Vibrations, or Undulations.

We must now think for a moment what is meant
by a Wave.
272 Tle Ocean of Air.

Most people have seen waves of the sea, on the
sea-shore. The general impression of a wave is of a
body of water, pouring onward, curling over, and
dashing high on the beach.

This is a mistaken notion. ._ Waves on the beach do
curl over, and do run up the sand or shingle, especially
when the tide is coming in. But the true idea of a
wave must be taken from the rising and falling of the
water a little farther out—say, near the end of a pier.

Watch a piece of wood floating. A wave comes
up, passes under the wood, and flows on, but does not
take the wood with it. The wood stays behind.

Nay, except on the crest of a breaking wave, you
may see the same thing close to the beach. There too
a piece of wood or seaweed will dance long in one spot,
wave after wave giving it a toss, and leaving it where
it was.

If a wave meant the actual onward movement of
water-particles, this could not be. The floating object
would be carried forward.

Instead of which the wood, and also the water-
particles among which it lies, are at rest. The wave
is a vibration travelling through the water-particles, not
a forward motion of those particles themselves.

Such a wave may often be seen travelling over a
field of corn. The separate ears of corn do not journey
forward. Each in turn bends under the influence of
the wave, but each remains where it was. Only the
wave changes its place.

Sound always springs from motion of one kind or
another. Some sudden movement of a body through
the air, or against another body, sets the air-particles
vibrating and quivering in little waves. These tiny
Sound and Light. 273

undulations pass on with great speed to particle after
particle of theair in all directions. A quick succession
of them strike at length on the drum of a man’s ear,
conveying certain impressions to the brain, which,
partly through long practice, the brain understands,
and translates into certain meanings.

But if there were no medium to convey the waves,
there could be no sound, however mighty the shock
might be of any two meeting bodies.

Once again, it should be clearly understood, that
in these waves there is no onward movement of air
itself. The particles of air remain where they were,
only they are tossed about a little in the passing wave,
as water-particles of the ocean are tossed about in
passing billows.

Imagine what it would mean if things were other-
wise—if sound-waves meant a literal -rush of air-
particles from the source of sound to the ear! Why,
a wind would be set going by every movement of
every body on earth, ten times more violent. than
the most desperate hurricane of a tropical cyclone.
No human beings or human dwellings could with-
stand it.

A good deal was said in the last chapter about rays
of light and heat not visible to our eyes. We saw how
the world, in even the darkest night-time of winter, may
be actually full of light, radiating from every surface—
if only we could see it !

The same may be said of sound. There isa scale
of Sound, as well as a scale of Light, consisting of
higher and lower notes. In these days of pianoforte
practice, the Sound-scale is a good deal more familiar
to people generally than the Light-scale.

We all know, from our own sensations, how

18
274 The Ocean of Air.

different are the high notes from the low notes of the
Sound-scale.

But what we do not know, is how much deeper the
scale of low notes may descend, or how much higher
the scale of high notes may ascend, beyond what we
are able to hear. Sensation only helps us so far as our
hearing extends; and asin sight, so in hearing, our
powers are very limited.

Some animals on earth seem to be utterly without
voice, without means of vocal communication. What
if this only means, that their voices are pitched too
high or too low for our powers ?

In a microphone—a microscope for sound—the
patter of a fly’s footsteps has been heard. If we had
keen enough hearing, we might listen to the patter of
every insect’s footsteps, to the munching of every
insect’s food, perhavs to the shrill small squeak of
every insect’s voice.

The power of hearing differs greatly in different
people. Without reaching actual deafness, there are
many degrees of acuteness. The ear-drum in some is
more sensitive than in others, and the brain is quicker
to interpret. Where even a slight degree of deafness
begins, the higher and lower notes, especially the former,
are at once cut off, and all fainter hissing sounds die out.
The inability to detect high notes may be tested at
any time by listening to a cricket’s chirp. Many
people, who are not supposed to be deaf, and who
would probably repudiate the charge with indignation,
will fail to hear it. If disposed to be over-positive in
small matters, they will perhaps deny the existence
of the sound, ascribing others’ consciousness of the
same to fancy. Nothing is easier or more common
among minds ofa certain calibre than the declaration—
Sound and Light. 275

‘Such a thing cannot be, because I do not hear or
see it.’

Deeper and higher notes in the scale of sound mean
less rapid and more rapid pulsations of air, larger and
smaller waves of air. All kinds of sound reach us at
the same rate of speed, but some sounds are formed
of bigger undulations than others, so that a smaller
number of waves arrive within a certain time.

About the deepest note commonly heard by the
human ear consists of sixteen waves each second.
About the highest note usually consists of some
thirty-eight thousand waves each second; but some
people, with hearing of rare acuteness, can detect
yet shriller sounds, as high as forty-two thousand
vibrations. The human ear commands altogether a
range of no less than eleven octaves.

This is by no means to say that other sounds do not
exist, higher and lower in the scale, formed of yet
larger and fewer waves, of yet smaller and more abun-
dant waves. The whole world may be full of sounds
which our ears cannot hear, as of light which our eyes
cannot see. What we call silence may be no more
actual silence, than what we call darkness may be
actual darkness.

Some of the most frequent causes of sound are
the sudden striking of one body against another; pro-
longed friction between two hard bodies; any kind of
explosion; and sharp discharges of electricity. All
these cause sound-undulations through air-particles,
and in a less degree through the particles of liquid and
even of solid substances.

It is very difficult to define where noise ends and
music begins. The music of certain uncivilized
nations, such as the tom-tom rattlings of the Hindoos,

18—2
276 The Ocean of Air.

are mere noise to cultivated ears. Yet, probably,
every continued and steadily-recurring sound carries
within it at least a possibility of music.

The human voice, listened to by one silent person
in a full room of talkers, presents a jangle of dis-
cordant sounds. But musical possibilities lie enfolded
there, undoubtedly.

A certain degree of speed and of regularity in the
vibrations would appear to be needful, before any
sensation of ‘ music’ can be produced in the listening
brain.

To return to Light and Heat, and what they are.

It is impossible to speak here so decidedly as about
sound. The same degree of proof is as yet wanting.
We do, however, believe that just as sound consists
of waves, so light and heat consist of waves.

Only, the waves of light are very much smaller
and very much more rapid than the waves of sound.

Sound-waves which we can hear, vary, as already
stated, from about sixteen in a second to thirty-eight
thousand in a second. But light-waves are to be
counted by millions in a second. A single light-wave
is believed to be only about one-five-hundred-millionth
of an inch in length.

The speed of the two is more easily compared.
Sound-waves travel through the air at the rate of
about one-fifth of a mile in each second. Light-
waves journey at the rate of one hundred and ninety-
swo thousand miles each second.

I have spoken of sound-waves as waves of air.
Now, light-waves are not waves of air. Light-waves
can pass through air, little hindered by it. Light-
waves can travel in distant space, where no air
Sound and Light. 277

exists, flashing from star to star, from sun >
planets, at the rate just named.

Still, if light consists of waves, they must be waves
of something. By ‘waves’ we mean certain move-
ments or undulations of an actual substance. If space
beyond our atmosphere were utterly and absolutely
empty, light could not travel in waves.

We believe that space is not empty. We believe
that everywhere, through the universe, is a certain
most fine and delicate something which has been
named @ther—infinitely more fine and delicate than air,
far too fine and delicate to be tested by any instru-
ments that man has yet made. This ether is supposed
to reach from earth to the sun, from the sun to all planets
and stars. It fills ali space, it pervades the atmo-
sphere, it enters into the make of all liquids and
solids.

Through this wondrously fine and invisible zther,
the waves of light are sent, vibrating, thrilling, oscil-
lating, quivering, down to earth from the blazing sun,
travelling with such marvellous speed that imagination
cannot picture it.

Whether light-waves, as such, do in very truth exist,
cannot yet be positively asserted. The wave-explana- .
tion may, in the future, have to give place to some
other theory.

We do know, however, that light travels in some
such mode, through some such medium. While we
cannot be certain that light actually comes in waves,
like sound, we know the speed of light, for that has
been measured ; and we know that light consists of a
certain definite number of somethings each second,
whether we call them ‘waves’ or no, for those some-
things have been counted.
278 The Ocean of Air.

Red is at the lower end of the light-scale, corre-
sponding with the deepest bass-note known to our
ears. Violet is at the higher end of the light-scale,
corresponding with the shrillest treble-note known to
our ears.

The exact pitch of any one musical note, or indeed
of any sound, depends entirely on how many waves of
sound pass into the ear in one second. For a bass-
note, the waves are larger and fewer; for a treble-note
they are smaller and more numerous.

It is the same with light. The exact colour of any
object depends upon how many waves of zther pass
into the eye in one second. For red, the waves are
larger and fewer; for violet they are smaller and more
numerous.

About thirty-nine thousand tiny light-waves in one
inch mean, as they reach the eye, the sensation of
red. About fifty-seven thousand waves in one inch
mean the sensation of violet. Between these two range
all other tints visible to human sight. Beyond them,
higher and lower, our seeing powers fail. Of course,
sight, like hearing, varies markedly in different people,
some having a far wider range of vision than others;
_ but these are generally accepted as the outside limits.

It should be noted that I am speaking now of the
size of light-waves in respect to space, not their speed
in respect to time. There are so many vibrations in
the second belonging to red, and so many belonging to
violet ; but these are enormously high figures. People
in general do not much care to hear about millions and
billions.*

* Red means about two hundred millions of millions of vibra-
tions every second ; violet, about seven hundred millions of mil-
lions each second.
Sound and Light. 279

Those rapid light-waves, coming from the sun,
which give to our eyes the sense of brightness, are not
by any means the whole of the keyboard. It has a far
wider range.

Beyond the red, low down, are other sun-rays, deeper
notes, known to us only as heat-rays. We can. feel
them as heat, but we cannot see them as light, because
they are formed of waves too big to affect our eyes.
Whether some animals may be able to see them is
another question.

Again, beyond the violet, high up, are yet other
sun-rays, known to us only as ‘chemical rays.’ These
are formed of waves too minute and rapid for our
powers of vision; nor are we conscious of their small
amount of heat. But the chemist is well acquainted
with these rays; and the photographer knows how to
use them on prepared sensitive paper, which—if paper
can be said to see—does see, or at least is affected by,
them. When the sun takes a man’s likeness, he does
it by means of these invisible chemical rays.

A ray of white light is a bundle of many colours.
When, by allowing it to pass through a prism, the ray
is broken up, the various tints of which it is combined
are seen. Instead of a single white ray, a series of
coloured rays are seen,—violet, indigo, blue, green,
yellow, orange, and red,—extending from the top to
the bottom of our sight-scale. The ear has command
of eleven octaves of sound; but the eye has command
of only about one octave of colour.

Not long ago it was the fashion to talk about the.
Three Primary Colours, Red, Yellow, and Blue. After:
a while these were altered into the Three Primary
Colours, Orange, Green, and Violet. Now all the
280. The Ocean of Air.

chief colours of the ‘spectrum,’ as given above, are
counted to be Simple or Elementary Colours, from
which all other colours are made.

Black and white are not colours. Pure black
means the absence of any tint at all: while white is
the union of all the rest. If you look at a mass of
soap-bubbles from near at hand, you will see all the
different hues of the light-scale, on the thin films of
soap and water. But if you go to a distance, the
colours will unite before reaching your eyes, and the
bubbles will appear white.

A ray of light passing through a prism is broken up
and ‘dispersed,’ each coloured ray which helps to form
it being bent and thrown upon the wall or ceiling at a
different angle. This is said to be done through
‘refraction.’ ;

If light-rays could not be refracted and dispersed,
we should lose all our sunrise and sunset tints. The
crimson of the clouds, the opal of the skies, the golden
glows, would be nowhere. A light-ray until dispersed
is always white. Red and yeliow tintings in the
heavens mean always the breaking up of white rays,
that some of the hidden brighter colours which unite
to form white light may become visible. This scatter-
ing of light, which produces not only the brilliant hues
of morning and evening but also the blue of the airand
the sky, is now believed to be largely the work of fine
floating dust in the atmosphere, assisted by minute
floating particles of water-vapour.*

* The deep blue of the Mediterranean, of the Lake of Geneva,
nay, of the Ocean generally, is believed to be due to the same.
cause—the scattering of light by minute ‘foreign particles’ always
present ; in other words, by floating dust. An authority writes :
‘Thin milk, when poured upon a black surface, appears bluish.
The milk is colourless ; that is, its bLlueness is not due to absorpfion,
Sound and Light. 281:

Dispersion of light is also markedly seen with rain--
bows.

For a rainbow to appear, there must be sunshine as
well as rain; and the observer must stand with his
back to the sun, his face to the bow. Any number of
observers may be present; and any number of rain-
bows. Each individual sees ‘a bow,’ and all speak of
‘the bow,’ but no two among them see the same bow,
because no two can stand in exactly the same spot at
one time.

A rainbow is caused by the reflection and refraction
of the light-waves on the falling rain-drops. Each
rain-drop acts as a prism, breaking up and dispersing
the rays of white light, so that a succession of tinted
rays are seen from violet to red. Each observer’s
eyes must be in the direct line between the sun and
those falling drops which, acting in quick succession,
serve for his prism. Sometimes the bow is single,
sometimes double. Sometimes the colours are more
clear, sometimes less clear. The conditions are the
same, however, for all observers gathered in one place,
and the effect upon their vision is the same; so that it
is as if all saw one bow.*

What a dull colourless Ocean ot Air our dwelling-



but to a sedaration of the light by the particles suspended in the
liquid. The juices of various plants owe their blueness to the same
cause ; but perhaps the most common illustration is that presented
by a blue eye. Here we have no true colouring matter, no proper
absorption, but we look through a muddy medium at the black
choroid coat within the eye, and the medium appears blue’—
Tyndall's ‘ Glaciers of the Alps.’

* One has written on this subject: ‘The first rainbow was seen
—or might have been seen if there had been anybody there to see
it—when the first sunshiny shower fell on this earth’ Yes;
doubtless. The bow was there; but not till the days of Noah was
it graciously ‘set ’—might one suggest the meaning as ‘indicated’?
—as a token in the clouds of the Divine promise.
282 The Ocean of Air.

place would be, if no light-rays could ever be broken
up, refracted or reflected,—if no crimson and purple
and golden hues lit up our evening skies, or shone as
rainbows through the rain-drops, to relieve the dead-
level of perpetual whiteness !
CHAPTER XXXI.
ATOMS AND MOLECULES.

PARTICLES of air, particles of water, particles of solid
substances, have been often spoken of in past chapters.

There is no such thing to be found on earth, or, for
aught we know, in the universe, as a substance which
is not formed of particles or little parts joined together.
There are no substances so uniform and solid in mass,
that they cannot by any possibility be divided.

Granite rock is hard; but granite can be melted or
broken, can be crushed, and even ground to powder.
Gold is hard and tough; but gold can be beaten out
to a leaf so thin, that a breath will blow it away.
Diamond is hardest of them all, but diamond can be
cut and altered in shape, particles of diamond being
removed from the main body.

Suppose you take a lump of soft sandstone rock,
and break it in two, then break the half, and again the
quarter, dividing and subdividing till you have a piece
too small to be divided further. Still that tiny lump
can be pounded, and only fine yellow sand remains.

Each grain of sand lying there is a particle: one of
the many particles which helped to make the lump of
rock.

A grain of sand is small. But put that grain under
a microscope: and, behold, it grows into a big jagged
284 The Ocean of Air.

rock, consisting of any number of minute particles. So
we are by no means at the end of things yet, with the
grain of sand. The only question with respect to
further sub-division is as to the fitness of the tools at
our command for such delicate work.

Each separate body upon earth, whether a solid, a
liquid, or a gaseous body, is believed to be made up of
countless multitudes of most minute particles of matter,
which are called Molecules. Each molecule is made
up of other still smaller particles of matter, which are
called Atoms.

A single molecule of any substance is exceedingly
small; smaller than the tiniest speck you can possibly
imagine. Yet a molecule is made up of atoms, there-
fore a molecule must be larger than an atom.

Suppose you have a drop of water. How many
molecules would you think there are in the drop ?

I cannot answer that question for you. The drop,
however, may be divided. You may have a smaller
and smaller drop, till you get down to one of those
minute specimens, which float in the air during a fog.
But it is still enormously far off from being only a single
molecule. Even such a drop, under a powerful micro-
scope, will be quite a little pond; and if taken from
a real stagnant pond, might contain living creatures.
The very tiniest and lowest of living creatures is
believed to be made of, at the least, somewhere about one
million molecules. You see what an immense number
of molecules must be in one ordinary waterdrop.

Now suppose that by subdividing the drop, or by
evaporating most of it, we could obtain the most
infinitesimally minute water-speck; so minute as to
be not only invisible but utterly incapable of any
further lessening or dividing.
Atoms and Molecules. 285

Then you would have a Molecule of Water. A
water-molecule is the smallest speck of water which
can exist, being still water. One may divide or sub-
divide, or lessen in size, any object, to a great extent;
but one cannot go on at that work for ever.

While a water molecule is the smallest imaginable
speck of water, and cannot be further diminished in
size, as water, it may be divided into something else.
It may be separated into the atoms of which the water-
molecule is made.

Heat alone will not do this. Heat can transform
solid water into liquid water, and liquid water into
gaseous water; yet the molecules of the ice, the water,
the vapour, are all alike in kind—are all the same in
make, the same in weight, the same in character. The
only difference is that they are differently arranged,
and placed nearer or farther apart.

You will remember that water is made out of two
gases: the good useful oxygen, so needful for com-
bustion ; the light hydrogen, so important for flame.
Each water molecule, each ice molecule, each vapour
or steam molecule, is alike formed out of one oxygen
atom and two hydrogen atoms, closely united.

I do not say that water is made of these two gases,
but owt of them. The two gases disappear, and water
appears instead. The simple oxygen molecules, made
of oxygen atoms, and the simple hydrogen molecules,
made of hydrogen atoms, are split up, broken to pieces,
and new compound molecules are formed. Each atom
of oxygen seizes upon and is seized by two atoms of
hydrogen, in a firm embrace. As this ‘ triple alliance’
takes place, and in the very act, the gas atoms and
molecules vanish ; and a new water-molecule has come
into existence. ©
286 The Ocean of Air.

Heat is the power which commonly brings about
new alliances of atoms. But if you want to break
up the water-molecules again, you must do some-
thing more than apply heat. A stream of electricity
poured through the water will break up each water
molecule into its original gas-atoms.

Much was said earlier about the Elements or Simple
Substances: those which cannot be broken up into
other substances. An atom must always be the atom
of a simple substance, never of a compound substance.
You may have an atom of oxygen or of carbon, of
hydrogen or of gold, of silver or of iron. You cannot
have an atom of water or of glass ; because the smallest
possible speck of water or glass is always formed of
two or more other substances. It is a molecule; not
an atom.

A rough calculation has been made, that about fifty
millions of hydrogen molecules, placed in a row, might
perhaps reach an inch in length.*

An atom is that which can never be divided, can
never be made smaller, can never be changed in nature
or form by any of the known Forces of Nature.

There is a great deal that is very singular and

* It has also been reckoned that about two millions of hydrogen
molecules in a row might extend to a m7l/dmetre in length; and
that about two hundred million million million of them might weigh
a milligramme. There is, however, no pretence at exactitude in
these statements. An Atom of Hydrogen, as the smallest and
lightest mass of matter known to science, is said to weigh one
microcrith, thereby forming a standard of weight among atoms and
molecules of different substances, the ve/az’ve weights of which are
well known. An atom of oxygen weighs about sixteen microcriths,
or sixteen times as much as an atom of hydrogen. An atom of °
iron weighs about fifty-six microcriths. An atom of gold weighs
about one hundred and ninety-seven microcriths,
Atoms and Molecules. 287

mysterious about the character of atoms, and their
union into molecules. The atoms of certain substances
have what is called ‘an affinity,’ an apparent liking, for
the atoms of certain other substances ; and this liking
is always mutual. Where the affinity exists, the atoms
of different substances will unite chemically, under
heat or some other force, to form fresh substances.
Where the affinity does not exist, no power on earth
will cause them to unite.

The atoms always unite in a particular manner,
after certain definite modes and proportions. Even
where this curious ‘ affinity’ is found between them,
they will not consent to be jumbled up in any sort of
mass.

Suppose you want to turn a quantity of hydrogen
and oxygen into water. You may bring together as
much of the two gases as you please, under the
right conditions. But you will never get the atoms
to unite in any other manner than exactly one of
oxygen to two of hydrogen.

The same peculiarity runs through all the atoms
and all the molecules of all different substances. Each
particular kind of atoms will combine with just so
many, never more or less, of certain other substances,
and with none but those.

There seems good reason to believe that each atom
of matter is in itself an infinitesimal magnet, with
its two or more poles. These poles, attracting and
repelling, will unite or refuse to unite with the poles
of certain other atoms. The question of ‘affinity’
among atoms may be, partly, a question of magnetic
poles.

So if things are as we suppose, the Earth as a
whole is one huge Magnet ; and that Magnet is made
288 - The Ocean of Air.

up of countless millions of millions of infinitesimal
atom-magnets !

All molecules of any one substance are believed
to be generally alike, in size, in weight, and perhaps
in shape. A gold molecule is like every other mole-
cule of gold, but unlike molecules of iron or glass. A
water molecule is like every other water molecule, but
unlike molecules of mercury or silver.

The molecules of each separate substance, yet more
the atoms of which they are formed, are different
altogether, in nature and in modes of action, from the
molecules and atoms of any other substance.

These differences seem to be sharply drawn. No
intermediate connecting links have yet been found.
Each kind of atom stands alone, clearly defined, per-
manent in kind, unchanged through countless ages.
Each atom, each molecule, has been stamped with
certain characteristics, made subject to certain rules or
laws. The inherent characteristics remain always the
same; the rules or laws are followed with the abso-
lute submission of lifeless mindless matter.

The molecules of a solid substance are held in place
by attraction—the Attraction of Cohesion or of Sticking
Together, spoken of in an earlier chapter—and they
certainly do seem to stick together. Yet in reality they
are farapart ; far, that is, in comparison with their size.

Every particle in a lump of iron attracts every
other particle; the power of cohesion binding the
iron dust into a hard mass. But every particle in the
iron also keeps aloof from all the other particles.
Probably no substance on earth is so solid that it
might not become more solid under great pressure.
In other words, the particles are never so near that
Atoms and Molecules. 289

they cannot be forced nearer. This is a fact, not so
difficult to realize with reference to a gas or vapour,
with reference to the light elastic Air in which we live,
but much harder to grasp with reference to a solid mass
of iron or stone or gold.
CHAPTER XXXII.
A BUSY WHIRL.

WE have seen how in the whole Ocean of Air there is
no fixity, no stagnation; except indeed where that stag-
nation reigns, which means death to the individual.
In the world of matter all is change and motion; and
in the restless enfolding Atmosphere of Earth this is
especially seen. Air, gas, water, flow to and fro in
ceaseless circulations.

But—to turn for a moment from our main subject,
the Air,—in a mass of stone or iron we should cer-
tainly expect to find repose.

Yet nothing of the kind is there.. Or at least ic is
the repose only of well-ordered motion.

Each separate molecule in a solid substance is
believed to be a tiny system of quivering atoms. Each
atom has its own minute perpetual motion, its own
pathway of incessant gyrations, as surely the result of
conflicting forces as the whirl of planets round the sun.

And as atoms tremble about atoms in their tiny
spheres, so molecules stir among molecules.

The molecules of a solid substance have no doubt
very limited movements ; but in a liquid they are free
to wander throughout the whole extent. The speed
with which they do wander may be easily seen, if a
small quantity of red liquid is put into a basin of clear
A Busy Whirl.’ © 291

water. The pink tint, carried by travelling: molecules;
will at once spread to all parts of the water.

The movements of air and gas molecules are yet
more untrammelled. If the gas is free, they fly widely
apart with the utmost haste. If the gas is confined
within a vessel, the molecules keep up a constant
cannonade of the vessel-walls, striking and rebounding,
in the effort to escape. The force of such a cannonade
in the case of heated water-gas, or steam, is well
known in these days of steam-power. A gas, in fact,
consists of ‘ molecules in motion ;’ when near together,
acting one upon another; when far apart, pursuing
their own paths independently; but always on the
move.

It has been calculated that when hydrogen gas is at
the freezing-point, its molecules rush about at the rate
of over two thcusand yards each second. As the gas
is heated, this speed rapidly increases.

Molecules of Air—that Air which you and I breathe
in a common sitting-room—are incessantly careering to
and fro, with great speed. Since they come into per-
petual collision, one with another, no single molecule
advances far in any direction without being turned back.

These molecule-movements must not be confused
with the general movement of Air which we call Wind.
The two are as distinct, as are the motions of iron-
molecules within an iron ball and the motion of that
ball as a whole when it is sent flying from the mouth of
a cannon.

By a collision of molecules, it need not be under-
stood that the molecules actually touch. Probably no
one particle of air, or of any substance, ever really
touches another. It is enough for collision purposes,
if two rush so close together, that the proximity is un-

Ig—2
292 The Ocean of Air.

endurable to their repellent natures—or at least to the
repellent side of their natures, since, like most human
beings, they have a repellent as well as an attractive
side. Each then rebounds from the other, to come
immediately into collision with the next molecule.

The probable or possible number of such collisions
has been roughly calculated, and it sounds a little
startling. For a molecule of hydrogen gas, not un-
usually heated, the medium length of peaceable travel
among its neighbours is held to be about the four-
millionth of an inch;* while the collisions themselves
number some eighteen thousand millions in a second.

The strong smell of ammonia is well known.
When we speak of the ‘scent’ of any substance, we
really refer to countless tiny particles of it, which
detach themselves and float away in the air, thus
reaching the. sensitive nerves of our noses. Now,
just as a little red liquid put into clear water will
spread fast through the water, so a little scent in a
room will spread fast through the room; yet not so
fast as one might expect.

Ammonia particles travel at a rapid rate. When
not hindered, they rush about at a speed of some six
hundred feet each second; so it would not take them
long to reach the farthest corner of the biggest room
ever built. Only, they always are hindered.

The Air hinders them. Each ammonia-particle
has to fight a fierce battle for every inch of advance,
striking against and rebounding from the particles of
air which oppose its passage. There really is plenty of

* Or, from another source: ‘ At the pressure of our atmosphere,
and at the temperature of melting ice, the mean path of a molecule of
hydrogen is about the 10,oooth of a millimetre, or about the 5th part
of a wave-length of green light’—J. C. M., Encye. Brit.
A Busy Whirl. 293

room for the ammonia-molecules among the air-
molecules, if only they would move quietly. But the
‘rhythmic dance’ of these minute specks of matter
seems to be highly excited, not to say combative,
in kind.

We have seen how great a power Heat is in the
wide Ocean of Air. Heat tells upon the motions of
all particles of matter. So much so, that it is some-
times said—Heat is Motion. The more hot any sub-
stance grows, the more rapidly its particles vibrate.

Suppose heat to be passing into a lump of ice,
steadily raising its temperature. The ice molecules,
already stirring and trembling, stir and tremble now
more vehemently. Also they begin to move farther
apart, leaving wider spaces between one and another.
The ice grows larger.

As more heat enters, the molecules vibrate with
greater rapidity, becoming still further separated. The
force of cohesion is thus weakened, through the
greater distances dividing the particles. Presently
they flow in and out among each other, and the solid
ice has become liquid water.

If yet more heat enters, the same course of events
is repeated. The whirl of liquid particles grows
faster and faster. The molecules separate more and
more widely; the attraction between them is lessened;
the water grows larger and lighter. Finally the
molecules break loose altogether from any semblance
of cohesion, repulsion winning the day. They rush as
far as possible apart, and the liquid has become
a gas.

But why should heat cause wider separation among
the particles ?
294 The Ocean of Aur.

Is it a matter of repulsion, strictly ?

In the Solar System, the sun occupies the centre,
and the planets revolve around, each in its own path-
‘way at acertain distance. The sun mightily attracts
the planets, drawing them towards himself; yet they
never fall in upon the sun, for another force is at work,
balancing the attraction, keeping each in its place.

This force is not repulsion. The sun does not
repel the planets. He only attracts; and the counter-
balancing force is the swing or impetus of each planet’s
rapid motion.

If the planets all began to go faster than at present,
they would all move to positions farther off from the
sun; and so the whole Solar System would extend in
size, would take up more space.

Now think of a lump of ice as a little system of
moving particles, not absolutely unlike the Solar
System of moving worlds.

When additional heat enters into the ice, the
particles, already in ceaseless motion, begin to move
more rapidly, and then—

Well, and then? Why, naturally, the swing or
impetus of each particle’s increased speed carries it a
little farther away from other particles. The dividing
spaces between grow wider. The ice as a whole
expands, taking up more room.

Heat appears to have worked this. Not indeed by
increasing the repulsion among the particles of ice,
but by causing them to move, to swing and circulate,
so much more vehemently, that each particle is carried
to a greater distance from its neighbours,—till the
whole melts into a liquid.

And as comets sometimes break loose trom the
Solar System, through the violence of their own rush,
A Busy Whirl. 295

so it is often with the molecules of a liquid. The
vibration is so increased by added heat that all mutual
attraction is at last overcome, and the particles fly
widely apart—as a gas. But for this possibility, there
could be no Ocean of Air.

The analogy between the two—between the move-
ments of worlds and the movements of molecules—is
at least suggestive ; if indeed the latter exist. But we
still have to make that proviso. The story of mole-
cules and atoms is a well-founded theory, a most
probable explanation, which meets the difficulties of
the case better than any other yet proposed. Whether
it will stand firm in the future remains to be seen.

These questions are now closely searched into, and
rightly so. One cannot look too earnestly into that
world of Nature, which is the Handiwork of our
Father in Heaven, the outward expression of His
Thoughts.

We have tried to find the reasons and causes for
many things seen in daily life. Rightly so, again!
All results spring from causes, and there are reasons
for everything on earth. Such seeking is not sceptical.

“With God, nothing is impossible!’ This we know;
and it stands to reason! He who creates can create as
He will; He can act through the forces which He has
created, as He will, also! But we know that our God
is a God of order, a God of law, as well as a God ot
love. Plainly it is His will that cause and effect should
be always united, always balanced, albeit not always
understood by us.

I have spoken earlier of many ‘shut doors,’ where
our steps are stayed, at least for the present. For ‘His
ways’ are ‘past finding out.’ Past finding out, so that
296 The Ocean of Air.

no more shall remain to be found out. Not past
looking into and examining. Not past finding ever
fresh wonders, ever fresh delights, ever fresh opening
of hitherto fast-shut doors, which shall land us on
the threshold of yet other doors, with locks that need
patient picking.

As many intervening causes as we care to picture
may seem to lie between any one ‘effect’ in Nature,
and the supreme First Cause. Turn, however, where we
may, search where we choose, we reach always at the
last a wall of mystery. Beyond that wall, it may be
nearer, it may be farther, yet never distant, is God
Himself—‘ upholding all things by the Word of His
Power.’
PART VII.
LIFE IN THE AIR-OCEAN,
CHAPTER XXXIII.
DUST OF THE AIR.

THE Ocean of Air, as we have already seen, is a
mighty carrier of fine Dust.

What an amount of dust there is in the world; and
how little we commonly consider where it all comes
from !

Clouds of dust, swept along by a March blast, are
suggestive of colds and coughs, no less‘ than of a good
harvest, worth a king’s ransom. ©

March dust is coarse, rough, gritty, a foe to eyes
and throats. Other kinds may be finer, yet not less
injurious. We hear of such dust in manufactories,
perilous scrapings and filings which float about and
are breathed into the lungs, to tell upon frail human
organs, shortening life. A deadlier dust, this, than the
wickedest road-grit of an English March. The busy
Air-Ocean bears all kinds to and fro. .

Dust is plentiful enough; not to say more than
enough; at all times and everywhere; a companion
which we labour to keep out of sight in our homes, but
which never can be exterminated.

Each grain or speck of dust, however small, is a
mass of atoms; and atoms cannot be put out of exis-
tence by any force at our command.

After all, dust may not really be ‘more than enough’
300 The Ocean of Air.

in quantity; if, as some think, it is absolutely needed
for the formation of every mist, every cloud, as well as
every fog. - We could not do without clouds.

Still, there is an aggravating persistency in dust.
Strive as we may, it is never got rid of. Open the
window to let it go, and the very Air which carries it
off brings in a fresh supply. Rub a mahogany surface
bright as a mirror—and, lo! before you can turn away,
tiny gray specks are settling down again.

In fact, the most we can do is to act the part of a
London policeman, with perpetual ‘ Move on!’ to the
little vagrants.

They do move on; no doubt about that! Dust is
never long at rest. Perpetual Circulation of Dust is
as true as perpetual Circulation of Air; though less
important to us.

There are many kinds of dust in the world; some,
such as gold-dust, having a market-value. But in
treating of common dust, gold may be put out of our
calculations; though doubtless a minute speck of it
does wander here and there through the depths of the
Air-Ocean.

We do not generally realize how full our rooms are
of dust. Unless the Atmosphere is unusually laden,
our senses do not make known the fact. Dust-specks
are for ever travelling here and there, up and down,
north and south, east and west, uncontrolled as the
winds themselves, in a continual restlessness. They
are always settling down somewhere, yet the air is
always crowded with them.

Most of this goes on unnoticed by us. But let a’
room be left a few days undusted, and results are patent
enough. Or let aray of bright sunlight stream in; and
a whole world of dancing many-hued motes is revealed.
Dust of the Air. 301

Where do all these motes come from ?

From everywhere; from anything; from all imagin-
able surfaces. As varied as are earth’s substances, so
varied are the kinds of dust floating in the Air-Ocean.

No substance, probably, exists which does not
under common conditions part with minute portions
of its surface; those portions passing away as fine
dust into the air. More or less everything crumbles,
everything wastes.

The wear and tear of friction in daily use make
dust. The rubbing of one body against another makes
dust. The progress of growth and decay makes dust.
The effects of frost, rain, and wind are to make more
dust. The mere action of damp, air, in even a repose-
ful mood, brings about the crumbling of hard surfaces,
and so makes dust. With certain substances hard
friction is needed to wear the surface, but in a greater
number there is a constant giving off of fine particles,
to be added to the array of dust. Above and beyond
all these sources, great quantities of Meteoric dust are
ever coming into our Atmosphere from distant Space.

These and other kinds float in the Ocean of Air; the
heavier motes dropping the soonest ; the lighter borne
to and fro indefinitely, even at vast heights above the
Earth. It has been already explained in earlier
chapters how the formation of fogs and clouds, the blue
of the Air, the fair colours of sunset, the brilliant hues
of the Aurora Borealis, are all believed to be more or
less due to fine floating Dust in the Atmosphere

If one could analyze the dust-specks collected in a
single room, curious results would be obtained. Among
a hundred motes, perhaps few might own to the same
source.

This, from a log of wood; that, from a mass of
302 The Ocean of Air.

metal; this, from the skin of a man; that, from the
fur of a beast; this, from a woollen dress; that, from
a shabby shoe; this, from the stem of a tree; that,
from the petal of a dying daisy; this, from a pile of
volcanic débris; that, from a chalk cliff; this, from a
coal in the fireplace; that, from the frond of a fern;
this, from a fallen meteorite; that, from the dried silt
of a river-bed; this, from the wing of a butterfly; that,
from the pollen-gatherings of a busy-bee; and so on,
ad infinitum.

Light substances are often carried to immense dis-
tances by moving currents of Air, especially in the
upper regions of the Atmosphere. Just as a quickly-
flowing river can keep earth and sand long afloat, so
rapidly-flowing streams of Air can keep fine dust aloft
for an almost indefinite length of time.

Great quantities of salt are carried by winds from
the ocean over the land. When gentle evaporation
takes place on a still day, the vapour passes upwards,
leaving its salt behind. But when winds stir the
surface of the sea, lifting waves, and catching away the
salt spray, they bear salt and spray together, sometimes
for many miles inland.

Towards the end of April, 1882, a very severe storm
reached our shores from America—happily not without |
previous warning, so that the damage done to shipping
was less than it might have been. The winds blew
furiously, amounting even to a hurricane in force.
Some gusts were known at Kew to travel at the rate
of seventy or eighty miles an hour.

A remarkable feature of this storm was its effect
upon the fruit-crops. Apple-blossoms in multitudes
were swept away, and those that remained had grown
Dust of the Air. 303

black as if with blight, while the young leaves might
from their look have been scorched by a withering
flame. In gardens and in woods the same was seen;
the foliage of plants, shrubs, trees, more especially on
the windward side, being shrivelled and blackened as if
with sudden decay.

This was not the result of sharp frost, for though
cold it was not frosty. What could have caused so
unusual a result perplexed many. Somebody offered a
suggestion that the salt-laden condition of the winds
might form a clue to the mystery; and in the next
report from the Kew Observatory, this idea received
strong support. In proof of its probable truth three’
interesting facts were stated.

At acertain place in Dumfries-shire, about fifty miles
from the North Sea, during strong east winds, the
presence of salt spray had been detected on the leaves
of evergreens.

A calculation had been made, as the result of
careful examination, that at Penicuik, near Edin-
burgh, ten miles away from the sea, every acre of land
receives yearly, through its regular rainfall, no less
than six hundred and forty pounds weight of salt.

In ocean storms, salt flung by the winds with water
into the air, often renders the atmosphere so dark that
sailors can see no way ahead. By a strong gale suck
salt spray might well be carried forty or fifty miles.

These facts help to explain the carrying of. salt
from place to place. But in truth the air is at all
times more or less full of salt, floating as fine powder
among the floating motes of the Air-Ocean.

If salt is thus borne to and fro, much more will fine
dust be the sport of breezes and winds.

Dust is frequently carried away from deserts and
304 The Ocean of Air.

volcanoes for hundreds or even thousands of miles,
before being dropped to earth. When it does descend
it may come down gradually, winning no particular
attention, or it may fall as a sudden ‘ dust-shower.’

Falls of dust have often taken place at Malta, at
Genoa, and in the south of France; and the dust was
commonly supposed to be African in its origin. On
certain occasions, however, when carefully examined,
it was found to be quite different from the ‘ dazzling
white sand’ of Sahara, being instead of a reddish-
yellow colour; and both in itself and in the microscopic
creatures it contained it was known to be a kind
peculiar to South America.

About the middle of the present century a tremen-
dous storm visited Lyons and Grenoble, bringing with
it the unusual phenomenon of red rain! ‘Blood rain’
or ‘blood-red rain’ people called it, though the tint
was not strictly so red as blood. Some of the rain
was carefully secured and put under the microscope.
The colouring was then found to arise from a large
amount of the reddish-yellow dust, mentioned above,
being mixed with the rain-drops, and lending to them
of its own reddish hue.* Many falls of so-called
‘blood rain’ had been known earlier, and nervous
people were greatly terrified by them; but for a long
while the simple solution of the puzzle was not dis-
covered.

Red snow as well as red rain is sometimes seen:
the colouring of the snow being due to a very minute
vegetable growth. Here again the busy winds must
have been at work, carrying germs.

The cause is not necessarily always the same in
either case. One famous historical instance of red rain

* The red of the dust was found to be due to iron-oxide.
Dust of the Air. 308

was at the Hague, in 1670. People generally regarded
the visitation as an omen of war and disaster; but a
physician living thereabouts looked into the liquid with
his microscope. Although microscopes then were not
what microscopes are now, he made out easily that
the water in itself was unchanged, but that it was filled
with countless myriads of minute lively red insects: a
kind of tiny water-flea. The only possible explanation
of their sudden descent from the clouds, was that the
winds must have caught them up elsewhere, brought
them from a distance, and poured them down with the
rain.

Early in the present century, a remarkable fall of
inky rain was known at Montreal in Canada. Here,
however, a solution of the mystery lay ready to hand.
Microscopes speedily showed that the blackness of the
rain-drops was due to soot. An immense forest-fire
had taken place far away, south of the Ohio River;
and prevailing south winds had borne masses of soot
from the great conflagration to the skies of Canada,
‘thence to be showered down, mixed with water, as
‘black rain.’

Few who saw them will forget the extraordinary
‘sunsets of November, 1883. Red and pink, orange
‘and yellow, green and purple glows were contrasted
often with streaks of ‘ebony’ cloud. One evening the
western sky would be all aglow with orange; another
evening the whole was bathed in crimson. The moon
‘was sometimes a clear steel-blue, sometimes a distinct
‘green. Even in smoky London magnificent sky-effects
were visible; and wonderful reports came from around
the world, from the Mediterranean and the Pacific.
from India and Australia, from Canada and the United
States. Those who rose at an hour to watch for

20
306 The Ocean of Air.

sunrise were rewarded by like visions of beauty. No
common conditions in the Ocean of Air could. cause
this display, lasting through many weeks.

A mighty eruption of Mount Krakatoa in Java had
taken place that summer; such an eruption as our
Earth seldom knows. For those near the spot it was
a terrible experience. Black darkness reigned for
‘scores of miles’ around ; there were fierce lightnings
and balls of fire, and ‘crackling noises’ in the atmo-
sphere mingled with continual crashes as from heavy
artillery. The sounds reached, indeed, to an utterly
unprecedented distance. Over ninety miles off, the
uproar was ‘simply deafening’; while it could be dis-
tinctly heard at Rodriquez, nearly three thousand miles
away.

Yet, strangely, the noise of these explosions, which
literally blew to pieces two-thirds of the mountain,
though audible over one-fourteenth of the entire surface
of the Earth, was not so overwhelming in the neigh-
bourhood of the volcano. No doubt the thick clouds of
dust filling the air deadened it, as a dense fog or thickly
falling snow deadens sound.

The vast mass of materials, belched upward in a
black cloud from the rent and shattered mountain, was
estimated to be about seventeen miles in height.
Pumice, dust and ashes, were rained lavishly upon land
and ocean for hundreds of miles around; all heavier
pieces and coarser dust falling comparatively near.
But enormous masses of ‘light friable glassy dust,’
carried to lofty levels in the atmosphere, were borne
away by winds to far distances.

Consequent on the great explosion a wave of water
fifty feet high was sent careering through the Strait
into the Southern Ocean: while an air-wave of ‘ un-
Dust of the Air. - 307

exampled grandeur’ went circling round the world.
On the very same day a ‘thin white mantle’ was
drawn over the blue sky for a thousand miles to the
westward: the sun shining dimly through like a dull
reddish lamp.

Then followed the remarkable appearances already
mentioned: green and blue and coppery suns; green
and blue moons; skies of gorgeous radiance; clouds
of ‘burnished gold, copper, brass, silver, such as Turner
in his wildest dreams never saw.’ We have already
seen how the common blue of the air, the ordinary
tints of sunrise and sunset, are believed to be largely
due to fine dust floating in the atmosphere—both dust
of solid. materials and liquid ‘ water-dust.’ Here, in the
abundant pumice-dust of Krakatoa, was an intensified
form of the same cause ; intensified results in the way
of colouring being thereby produced.

The masses of dust travelled fast. Mounting toa
great height, above trades and anti-trades, they were
caught in the embrace of a ‘ full fair easterly gale,’ an
‘unresting hurricane,’ the very existence of which had
not before been conjectured, and were hurried with
extraordinary swiftness round the earth. The whole
tour of the equator was accomplished, it is believed, by
these clouds of volcanic dust in less than a fortnight,
and still they circled round and round for many weeks,
even for months, giving to mankind the grand sky-
displays of that year. Gradually the dust became dis-
sipated in all directions; but as for dropping to earth,
that is a slower matter. No reason is known why
dust, once lifted fifty or sixty miles above earth’s sur-
face, may not remain there for years.

In Holland and in Spain, dust-material brought
down by snow and rain, at the time of these radiant

20—2
308 The Ocean of Air.

sunsets, was examined. In both cases it was said to
contain volcanic dust, apparently agreeing in kind with
the ashes thrown from the crater of Krakatoa.

Dust-storms in India are of common occurrence.
Sometimes they advance as ‘a broad wall of dust, com-
posed of a number of separate columns,’ each column
being a small whirling cyclone of wind, thickly laden
with dust. Such a column may be seen only five or
six feet in diameter, and fifty or sixty feet high.

Electricity has no doubt a hand in these storms.
A regiment on march in the Punjaub was once caught
in a severe dust-storm, followed by rain and lightning.
As the rain came down, the tips of the men’s bayonets,
and the peaks of the caps worn by the officers, were
seen shining with a curious electrical light.

Enormous quantities of dust are swept up from
earth by the upward-whirling motion of these small
cyclones, and are often borne to an extraordinary
height. It has been doubted whether dust-showers alone
would account for nearly so much as is carried aloft.

Dust-storms are known to Australians, as well as
to inhabitants of India; and everybody naturally con-
nects them with deserts. With respect to Egypt, we
read—‘In the early spring the khamseen does indeed
afford a very unpleasant change to comment upon. It
is a hot dry wind, laden with fine particles of dust,
which penetrate everywhere, fill one’s eyes and ears,
irritate the skin, and produce a sense of extreme dis-
comfort. Everything is seen through a lurid haze.
The sands of the desert are whirled by it into rotating
columns, which march to and fro till they suddenly
break up and disappear. On the river this is merely a
cause of annoyance, but in the desert it becomes a
Dust of the Air. 309

serious danger. Caravans are said to have perished
and been buried beneath the drifting sands.’*

The ‘khamseen’ of Egypt is identical with the
‘simoon’ of Arabia; and the burning ‘sirocco’ of
Italy is believed to be the same, only ‘ tempered by its
passage across the water.’ The following sketch of a
so-called ‘sirocco’ from the pen of a French army-
surgeon, accompanying French troops in North Africa,
sounds like the genuine desert-blast :

‘It was towards the end of July, 1846. Several
soldiers had succumbed to the heat. The sirocco
assailed our little column. Under the influence of
this dry heavy and enervating air, the breathing be-
came difficult, the lips and the nostrils, cracked by
the burning dust driven up by the wind, were both dry
and painful; and the throat, as it were, became con-
tracted. The face was burnt by gusts of heat, some-
times followed by tremor and a fainting away which
resembled syncope. The perspiration ran off in streams,
and the water which was eagerly swallowed did not
quench the thirst, but increased the stomachic pains
and the difficulty of breathing. To walk would have
been impossible; we felt half suffocated under cover of
the tents; and in the open air the burning breeze
caused a choking sensation. . .. But for the water,
our column must have perished.’f

The simoon of the desert is worst and most frequent
at the time of the equinox. Commonly it is first seen
as a distant black spot, which rapidly draws nearer
and grows bigger. Then a rush of burning sand-laden
air arrives, from which birds and beasts flee in abject
terror. A camel turns his back to the blast, and if

* “The Land of the Pharaohs.’
¥ ‘The Atmosphere ;? by C. Flammarion,
310 The Ocean of Air.

possible finds a bush to shelter his face. Simoons
vary greatly in degree, some travellers having met with
far slighter ones than others. At the best the scorch-
ing air and drifting sand cause much bodily discomfort;
but at the worst they mean extreme peril to life..

Early in the present century an entire caravan,
consisting of two thousand men and eighteen hundred
camels, were all overwhelmed and suffocated by a
simoon. It is believed that the fifty thousand soldiers
sent by Cambyses against the Temple of Jupiter
Ammon perished in the same way.

One can well imagine the difficulty of breathing
such burning air, thickly filled with fine particles of
hot sand. It is, in fact, the same danger as that en-
countered by the American caught in a blizzard—the
danger of being stifled. Human lungs are not made
for densely-thickened air, whether the thickening arise
from cold snow-dust or from scorching sand.
CHAPTER XXXIV.
LIVING DUST OF THE AIR.

AmonG the dust-specks which fill the Air are other
minute things, not strictly Dust; smaller far than the
motes which we can see; invisible except under a
microscope; and altogether different from mere dust,
because they have in them the gift of Lire. These
make their home in the Atmosphere, floating every-
where, mingling with the air-particles in countless
multitudes. It has been stated that with every single
breath a man breathes he may draw scores or even
hundreds of them into his lungs; yet they are so minute
that they do not put him to inconvenience.

Many of these living germs of the air, infinitesimal
rod-shaped forms of vegetable life, are less than the
hundred-thousandth of an inch in length. They are,
however, exceedingly active, and frightfully prolific.
One of the Bacteria has been said to increase in the
course of twenty-four hours to over sixteen millions !

Some kinds grow by rapid dividing and sub-dividing;
each rod-like thing becoming two, which two divide
each into other two, and so on.

Others increase by means of spores. As spores
they can endure wide variations of cold and heat.
They may even become perfectly dry like dust, seem-
ingly dead; yet afterward they will revive.
312 The Ocean of Air.

This constitutes a danger to mankind. For air —
abounds in such germs and spores; and water is per-
haps fuller still.

They are germs of putrefaction often; germs of
disease sometimes. If any vegetable or animal food
is left within touch of air or water, wandering germs
will speedily seize upon it, feed upon it, ‘ turn it bad,’
as we say. Food, to be saved for any length of time
from these destroying multitudes, must be shut off
from the touch of water or air, hermetically sealed
in a dry vacuum. But men cannot be so guarded
from wandering germs of disease.

It is extraordinary how long such germs, or at least
the spores of them, will keep their vitality. In the
olden days of plague-visitation, clothes from a plague-
stricken district were sometimes buried fur months,
even for years; and when disentombed, infection broke
out anew. Scarlet fever germs, diphtheria germs, may
be conveyed from one person to another, through dress
or books or contact, or they may simply float to and fro.
in the air, waiting to find a victim.

Some allusion has been made earlier to the dangers
of great masses of decaying vegetation. The miasma
or malaria of marshy lands is only too well known
to travellers. :

Much mystery still hangs about the matter. That
a close connection does exist between marsh lands and
certain diseases in warm climates is undeniable; while
the exact nature of the connection is not so clearly
understood.

Decaying vegetation gives off certain gases, in-
cluding carbonic acid gas; but though the latter may
suffocate a man, it does not bring on intermittent fever,
nor do any of its companion gases, released at the
Living Dust of the Air. 313

same time. The ‘miasmata’ poured forth by decom-
posing vegetable matter are minute living disease germs,
which, carried by the air, fasten on human beings and
lay them low.

A certain amount of heat and of moisture are
generally counted needful for the development of the
poison; yet sometimes it is poured forth from under-
ground dampness, through cracks in a dry and hardened
earth. If no cracks exist, the miasmata are imprisoned
by the hard crust. Again, if the dampness is so exces-
sive as to cause a sheet of water over the surface of the
ground, the water acts as a guard, preventing the escape
of the germs.

These germs of disease when free, we are told,
‘may be carried on the pollen of marsh flowers or on
cryptogamic dust, along the valleys or up the mountain-
sides. Just as ordinary dust drifts into places here
or there, leaving other parts free, so does the disease-
laden dust settle in favourable spots.’ And, again,
‘In the vapours of the night, in the dews of the morn-
ing, the germs of the disease maintain their vitality,
and in the sultry breeze may be disseminated far and
wide.’*

They are seldom known to ascend above fifteen
hundred or two thousand feet, and their spread is
checked in a remarkable manner by trees, or indeed
by any substantial obstacle. Commonly they do not
invade large cities; but to this rule there are ex-
ceptions.

The Campagna di Roma 1s famous for its terrible
malaria. Evil vapours arise from the ground, especially
near the Lake of Solfatara, and in the height of summer
malignant fevers are so rife as to make the whole

* Mrs. Priestley.
314 The Ocean of Air.

Campagna a dangerous place of residence. Many of
the country people then flee to Rome, though that
city does not escape occasional visitations of malaria
fever. Probably the destruction of surrounding woods
has made matters far worse than some centuries ago.

Travellers in malarious districts should never leave
their houses till the morning fogs have melted away,
or stay out of doors when the evening mists begin to
form. Many an Englishman, impatient of restraint
and unbelieving as to the need for care, has fallen a
victim to the neglect of this simple rule.

Thus we see that the Air which brings us so many
good things brings us sometimes bad things also.
There can never in this world be a power for good
which is not also a possible power for evil. That
which tells one way beneficially will always tell the
other way hurtfully. When a gentle old lady, re-
commending her pet medicine to all her friends, says,
‘It may do you good, and it can’t do you harm!’ we
know that she is declaring an impossibility. That
which cannot do harm—if such a thing exists—is of
necessity no less incapable of doing good.

Air carries injurious dust, noxious gases, germs of
putrefaction and disease—this is true. Yet mainly
and on the whole, those things which the Air bears
upon its broad wings are for the benefit of living
creatures. If we wilfully place ourselves in the path
of evil things, they will be brought to us; but if we
take reasonable precautions, if we give the air liberty
to act, they will as a rule be borne away. There is no
purifying power like that of the free wild breezes.
Shut-up and stagnant air is another matter.

A common dust-mote remains for years, even for
centuries, the same. It may stick to some other body,
Living Dust of the Air. 315

or become detached from it, but in itself it does not
change : it cannot grow; it never gives birth to another
dust-mote. It has not the mysterious gift of Life.

And the Living never springs from the Not-Living.
We have around us a World of Life, also a World of
Lifelessness. The two are utterly divided, absolutely
apart. That which has not life cannot give birth to
that which has life.

For a long while this was doubted. Time after
time, vegetable substance was hermetically sealed in
a vessel, which was then so heated as to kill—it was
supposed—every kind of living thing within. Yet,
weeks later, when the vessel was opened, living germs
were there. So, it was concluded, they must have
somehow sprung to life from unliving matter.

But now we know that these tiny air and water
germs will live through enormously greater heat than
was once believed possible. The germs, found alive
when the vessel was opened, were simply the descen-
dants of earlier germs, not killed by the heat.

Closed vessels, containing a vegetable solution,
have since been subjected to greatly increased heat,
and when after awhile they were opened, no living
things were within. All the germs had been killed,
and so no fresh forms had sprung into existence.

There is a wonderful demarcation between Vege-
tables and Animals, yet the two worlds of Vegetable
Life and Animal Life have each a gentle slope leading
down to the margin of the other. On the margin
creatures are found which may equally well belong to
either side.

No such gradual slope, no such doubtful belt,
appears to divide the World of Life from the World
of Lifelessness. A sheer gulf separates the two.
316 The Ocean of Air.

That which has Life gives birth to that which has
Life; but the Living never springs from the Not-
Living. However low and small, however wanting in
organs and powers, certain live things such as the
germs of the Air may be, they are cut off by an im-
passable chasm from the world of inanimate matter,
the world of rock, stone and metal, of water and of
air.

True, the Not-Living materials pass into and out
of the bodies of the Living. True, air and water,
carbon and oxygen, have a share in the building up of
living structures. True, man and beast are literally
made of dust and water, so far as the physical frame
is concerned. ‘ Dust thou art, and unto dust shalt
thou return,’ was no mere figure of speech as uttered
unto man.

‘But Life is not in the dust, not in water, not in air.
Man is largely made of carbon, and a diamond is
formed of the same. Yet in the one we have the
presence of Life, the command of a controlling Will,
the ever-present joy or pain of Consciousness. In
the other we find no life, no will, no consciousness.
None can bridge the gulf between the two. None can
breathe the Breath of Life into lifeless matter, save
He who is THE LiFe]
CHAPTER XXXV.
INSECTS OF THE AIR.

From countless myriads of invisible germs, floating
and multiplying in air and water, we pass upward to
higher and more complex beings—the Winged Insects
of the Atmosphere. _

The Ocean of Air is an Ocean of Life, teeming
with creatures that breathe and move. These are of
all kinds. Grade by grade, from lowest microscopic
organisms, they rise in a steady progression, through ’
creeping and fluttering things innumerable, till higher
stages are reached.

The Insects of the Air! Multitudinous forms of
life are included in the term.

‘Insect’ is a word often used loosely, often wrongly
applied. Spiders are commonly called ‘insects,’ yet
really they are nothing of the kind. The same mistake
is made about woodlice, centipedes, and other creatures.

A true insect, among divers characteristics, must
always be divided into three parts, the head being so
far separate as to move independently of the body.
It must also have six legs, and two antenne or feelers.
It must breathe by means of air-tubes instead of lungs.
It must pass through a succession of changes leading
on to the perfect winged state.

A spider has eight legs instead of six, so it cannot
318 The Ocean of Air.

be an Insect. Also, if you examine a fly and a spider,
you will see at once how freely the fly can turn and
twist his little head about, while the spider’s head is
part of his body.

The breathing tubes of insects are very curious.
They are made of an exceedingly thin membrane or
skin, and they are kept in shape, always open for the
passage of air, by a kind of stiff thread, like very fine
wire, wound in close spirals within the tubes throughout
their whole length. These tubes pervade every part of
an insect’s body, even the legs and feet. The smaller
tubes run into bigger ones, and the biggest lead to
little openings or holes in the sides of the insect,
through which air passes in and out. Insects can no
more live without plenty of Oxygen than men
can.

To give in a single chapter any full details of the
enormous hosts of winged insects which throng the
Ocean of Air is a simple impossibility. Their names
alone, in a dry monotonous list, would far overflow the
space I have to spare. Chapters might be filled with
short descriptions cf British varieties, letting alone
those offoreign lands. But to see the Insect in its full
power and beauty, as well as in its full unpleasantness,
one must journey towards the tropics.

The Mosquito-misery is pretty well known to all
travellers in South Europe at certain seasons of the
year, as well as to all dwellers within the tropics.
Anglo-Indians are apt to wax eloquent, describing
past wakeful nights, vain hunts after a vanishing foe,
frantic endurance of a shrill unquenchable buzz, and
spotted swollen faces for many a day following.

Yet the mosquitoes have their use. ‘ Devouring
travellers is not the normal occupation of the mos-
Insects of the Air. 319

quito.’* It is merely a little passing entertainment,
belonging to its last and highest stage of existence.
Before becoming a Perfect Insect the mosquito dwells
under water as a grub or larva, and there it feeds
vigorously upon minute specks of decaying substance,
thus helping to render the water pure.

Of all Insect-pests none is greater than that of the
Locust—a creature seldom met with in England.
Some few locusts appear, perhaps, every year; but
many reported as such are really some other insect
mistaken for the distinguished foreigner.

In hotter lands the Migratory locust is a fearful
scourge. When once the warning signs are noted of
the coming peril, no human power can avert it. Nothing
but a change of wind is of any avail. Where the air-
currents flow, there the locusts go, helplessly, and as
if without will or steerage power. Countless hordes of
brown creatures darken the atmosphere. Opposition
seems useless, for nothing turns them aside. Brush-
wood over a wide tract is set blazing, and still the
mighty swarm sweeps by, myriads upon myriads dying
in the flames, while yet the army, as a whole, seems
undiminished.

I have spoken of their advent as a ‘peril,’ and so
indeed it is, not directly, but indirectly, a peril to
human life. For when once the locust-army settles,
the country around is doomed: grain, fruit, vegetables,
leaves, flowers, all are ruthlessly devoured. A visita-
tion of locusts in the East means a famine to follow.
Cattle die for lack of food; so meat, as well as corn
and vegetables, fails.

Parts of Southern Europe have often suffered from

* J. G. Wood. The greater number of facts in this chapter are
culled from his delightful ‘ Insect’ volumes.
320 The Ocean of Air.

locusts ; but it is in Asia and Africa that they are seen
in fullest force. One vast array of Indian locusts ex-
tended in length to no less than five hundred miles;
and as the swarm flew by, the air was so darkened
that big buildings only two hundred yards off were
almost blotted out. ;

Other insect-plagues might be mentioned also.
There is the fly-torment of a hot summer and of
tropical climates. There are wasp-torments, cockroach-
torments, spider-torments, the worry and distress to
human beings of almost any kind of superabounding
insect. More serious pests than these exist in such
creatures as the famous ‘tsetse’ fly of Africa, which
exterminates with itsdeadly bite all large quadrupeds
throughout the district where it lives. If ever the
‘tsetse’ makes its way to British shores, and finds
British air to agree with its constitution, then good-
bye to our flocks of sheep, our herds of cattle, our
fine breeds of horses! Not one of them could stand
against the tsetse.

Among the fairer and more innocent creatures
which float through the blue depths over our heads,
the short-lived May-fly is perhaps one of the most
abundant. Asa perfect insect it lasts commonly but a
few hours. Since no food is needed for so short an
existence, it has no mouth. The brief span is passed
in a merry, though monotonous, dance upon the
summer air. In some parts of Europe May-flies have
multiplied to such an enormous extent, that their little
dead bodies have been gathered into piles and used for
manure.

Dragon-flies, often called Horse-stingers, are most
harmless creatures so far as quadrupeds and men are
concerned. The idea that they possess stings is a
Insects of the Air. : 321

popular delusion. The long quivering bodies are power-
less to do an injury, and if they could bite they do not.
No doubt in the Insect-World a different tale
would be told, for the Dragon-fly is a ferocious wild
‘beast, a veritable dragon, there. In all the different
stages of his existence he is voracious to a degree, and
in the latest full-blown stage he is as ready to make a
meal of spiders and centipedes as of smaller insects.
One African dragon-fly is bright red in colour, with
brilliant opal-hued eyes. Another, a native of India,
has brown upper wings, the other two being of ‘ vivid
metallic green.’ Again, a dragon-fly of Borneo
possesses wings ‘ crimson, blue and green, according to
the lights in which they are viewed.’ Evenin England
we have a kind, the wings of which glitter ‘with
iridescent hues of metallic purple, green, blue and
‘gold.’ It is a pity that all these radiant colours fade
after death.

‘Many insects are helpless ina strong breeze: but the
powerful wings of the dragon-fly, beating the elastic
air, are equal to this emergency. Like a vigorous
rower, delighting to make way against a rapid stream,
‘the dragon-fly seems to rejoice in mastering the wind.

A remarkable piece of mechanism exists in the
wing of the dragon-fly. We all understand how a
‘rower makes his way. With the stroke that sends him
‘forward, he presents the breadth of his oar to the water,
‘so as to have a strong pull against it. Then instantly
the ‘ feathers’ his oar, letting the water-resistance act
only on the edge of the blade. But with the vigorous
‘strokes of a dragon-fly’s wings—how is it that the up-
~ward stroke does not exactly neutralize the downward
stroke, so as to keep the insect just moving to and fro
in one place?

aI
322 The Ocean of Air.

Simply because they are not mere up-and-down
strokes. By a wonderfully delicate mechanical arrange-
ment—a kind of little muscular spring—the wings are
‘feathered’ with every upward stroke. The down-
stroke makes full use of air-resistance, to send the
insect darting forward. But in the up-stroke the edge
of the wing slips through the air, meeting with slight
opposition.

Insects in general do not merely float on the air, like
balloons, through excessive lightness. Most of them
are so light and weak, that a breeze sweeps them away ;
yet each has its own weight; and each in perfectly
still air would sink to the earth, but for the ‘ rowing’
action of its wings. A common house-fly beais the air
about six hundred times each minute, thus making a
continuous humming sound.

Without some degree of weight there cannot be
real flight.

The helplessness 01 1ocusts in their migrations has
been mentioned earlier. They do not fly like dragon-
flies against the wind, but are swept along by it.

Locusts generally are not good for much in the way
of flight. When about to depart on a long aerial
journey, they make preparation by ‘ blowing themselves’
full of air,* so full that the air-tubes of their bodies,
generally flat, bulge out and become rounded. This
makes them lighter than usual, to begin with. Then the
exertion of flying heats their bodies, and the air in the
air-tubes grows warmer, therefore lighter. The locust
thus really does float partly through lightness, as used
wrongly to be supposed of all flying creatures. But the
very fact that it does so, makes it to some extent like
a balloon, the mere sport of the winds.

* Professor Duncan’s ‘ Transfoimations of Insects.’
Insects of the Air. 323

We have in England some Insects which can fairly
compete in appearance with their brethren of foreign
lands: but it is not so with butterflies.

Think what our world would be without flowers or
butterflies, without fair ornaments of the Earth and of
the Air-Ocean. Certain unlovely insects help to purify
the physical Atmosphere ; but beautiful things, such as
flowers and butterflies, help to soften and purify the
mentalAtmosphere. Is onemore needful than the other?

Butterflies in countless varieties are known to us,
from the tiny blue thing skimming over English
meadows, to its splendid cousin of the Himalayas, with
radiant tailed wings, peacock-marked in shaded blue
and green.

One exquisite native of tropical America, we are
told, ‘seems to partake with the gems the full glory of
colour. It is scarcely possible to conceive of a living
creature that can surpass this insect in absolute
magnificence. . . . The upper surface is radiant azure, ~
as if composed of a sheet of thin mother-of-pearl. When
the light falls in the right direction, the colour is so
intense that the eye can scarcely endure its radiance.’

And again of another, we learn,—‘ The upper
surface of this butterfly is rich shining opaline blue,
with a decided dash of green in some lights. The
wings are edged with a broad band of black, in which
is a row of little white spots.’

Another fine creature, found in South America, is
known as the Owl Butterfly. It is very large in size,
the wings being on the outside a chocolate brown, shot’
with blue and green. The curious part of this butterfly
is the under view. There, when the wings are well
opened, a distinct-and remarkable picture of an owl’s
face is seen.

2I—2
224 The Ocean of Air.

The general surface is dun-coloured, with brown
mottlings.. In the centre of each lower wing is a
painted eye; and the body of the butterfly ‘serves
perfectly for a beak.» A preserved specimen of this
creature is—or was recently—to be seen at the Crystal
Palace. I can vouch, after sight, for the ‘striking
resemblance to the face of an owl.’

The Dead-Leaf Butterfly is a no less singular
instance of imitation in form, so often seen among
Insects. This kind belongs to the Himalayas, though
found elsewhere also. When open and in the act of
flight, there is nothing unusual about it, but when the
wings are closed, and the animal is still, there is every
appearance of a dead leaf, brown and veined. A dried
specimen in a glass case, sent home years ago from
India, has drawn often the remark from a passing
observer,—‘ Why, you’ve got a dead leaf in there!’

A very different kind of Insect from the butterfly
displays the same tendency to imitation in appearance,—
I mean, the Walking-Stick Insect. Some creatures
of this kind are the most complete copies of dried
sticks: and certainly are more curious than beautiful.
They are among the largest known Insects. One
variety is as big round as a man’s thumb, and when its
legs are outstretched it is fifteen inches long. Another,
found in New Guinea, has hind-legs, the thighs of
which are half-an-inch thick, and over an inch and a
half long: while its eggs rival those of a humming-bird
in size. -It has big scratching body-thorns or spikes,
and sharp leg-prickles.

On the whole, one would prefer not to come across
any such monster insects in our English woods or
meadows !
CHAPTER XXXVI.
BIRDS OF THE AIR.

THE Birds of the Air! How natural an expression it
seems! We talk of ‘the birds of the air’ involuntarily,
as of the ‘fishes of the sea’ and the ‘beasts of the
earth.’ Practically, as more than once stated before,
all living creatures are creatures of the Ocean of Air,
since all breathe air, none can live without air. But
the Birds, living on the very wings of the wind, de-
lighting to soar into highest regions of the Atmo-
sphere, are in the fullest sense Inhabitants of the
Air. ;

Birds do not merely float on the air, any more than
do insects. No insect, even, is lighter than perfectly
still air; and no bird exists which is not very much
heavier than air. A balloon floats because of its
lightness, and so becomes the helpless sport of the air-
currents. A bird can resist and struggle against a
wind.

True, birds are light in make, with hollow air-filled
bones. If not so, each bird would need much longer
wings and much stronger muscles than are now
necessary. But its weight is shown by the fact, that if
wounded and disabled when flying, it at once falls to
the ground. A bird actually lighter than air would
float still, even when wounded. Since it keeps itself
326 The Ocean of Air.

up through active exertion, it drops when active
exertion becomes impossible.

When a man rows himself over a lake, he is not
merely floating. The boat does float, but it does not
- advance by means of buoyancy. The man propels the
boat by using the resistance of the water. He pushes
the boat forward by pushing against the water.

A bird does this, and more. The bird not only
rows itself forward, but also raises itself upward, and
keeps itself aloft by actual force. A bird’s flight is a
question, not of lightness, but of force against force.
It uses the resistance of the air, as the rower uses the
resistance of the water. No bird could flyin a vacuum,
even if it could live there. The wings would -have
nothing to push against.

Wing movement is often extraordinarily rapid.
Even the heavy slow heron flaps its great pinions at a
rate of a hundred and thirty or forty strokes each
minute—twice that, if we count the upward as well
as the downward motion. Small birds—particularly
pheasants and partridges—vibrate their wings with
such speed, asto leave ‘only a blurred impression on
the eye.’ In other words, each flap remains upon the
retina of the eye until the next comes to mingle with
it.

A bird is actually forced forward by the elasticity
of the air. Like water, only to a greater extent, air
may be compressed ; but there is always in both fluids
a quick rebound or reaction. The wings of a bird
striking downward compress the air sharply: and the
instant expansion of that compressed air drives the
wings on, sending the bird with them.

For this purpose the wings are both strong and light
in make. They are also joined to the body at such an


Peete

flight of Sea-Birds. From a photograph by B. Wyles & Co.
Birds of the Air. 327

angle that each stroke necessarily sends the bird
forward. A bird cannot fly backward, for the whole
set of the wing and the wing-feathers is against such a
motion. It may drop backwards, yielding itself to the
influence of gravitation, and only guiding or steadying
itself by wing-movement ; but actually to fly backwards
is an impossible feat. Nor can it rise upward except
head foremost. Merely to float upwards, in any sort of
position, is again beyond its power. The first rising
from the ground implies a certain amount of vigorous
exertion, which in the case of very large and heavy
birds becomes an actual struggle. Once aloft and
under weigh, they sail onward easily enough.

The same difficulty which we saw wonderfully met
in the case of the dragon-fly recurs here. If each
downward stroke of the wings forces the bird onward,
how is it that each upward stroke does not undo the
work of the last downward stroke, forcing the bird
equally far backward? In a bird there is no curious
mechanical arrangement for ‘ feathering’ its feathered
oars at every stroke.

One answer has been given already. The set of the
wings altogether is such as to render forward motion
easy, backward motion difficult.

Also, a bird’s wing is. rounded or convex on the
upper side, hollow or concave on the under side. By
the downward stroke it encloses and compresses air
vigorously ; while in the upward stroke air flows over
the edges and escapes all ways.

Moreover, -a beautiful contrivance is seen ‘in the
arrangement of the feathers. They are: made'so to
underlap one another, that, when the downward stroke
takes place, the compressed air below forces them into
a more compact shield, through which little or no air


328 The Ocean of Air.

may pass. But when the upward stroke takes place, a
precisely opposite effect isseen. The feathers then open
and part asunder, and the air streams freely through.

Who does not see a mighty Master-Mind at work
in all these wondrously delicate adjustments of Nature?
Who will not if he will ?

Birds do not always fly with quick and vehement
wing-vibration. Sometimes, seated by the sea, one
may see a gray and white sea-gull lying calmly on the
air, its heavy white waxen body floating apparently
like a feather, with outstretched wings, scarcely stirring.

This is a feat in which some birds are very much
more expert than others. In an absolutely still atmo-
sphere it would not be possible; but air, as we have
found earlier, is seldom, if ever, absolutely still.

The effects of wind may be produced in two ways :
either by the air flowing against motionless objects, or
by objects moving through motionless air.

Now here is a practical carrying out of that prin-
ciple. A bird keeps itself aloft by striking its wings
against the air, so using air-resistance to overcome the
gravitation which drags it earthward. But suppose a
wind is blowing against the bird when it is aloft; ifthe
bird is sufficiently dexterous it may so use the resistance
of that moving air against its outspread wings, placed
at a certain angle, as to overcome the attraction of
earth, and yet to remain still. It is a most delicate
and scientific operation, and many birds are incapable
of attempting it. The kestrel, as well as the sea-gull, is an
adept at such soaring, and so also is the mighty albatross.

‘ Those who have seen the albatross,’ writes the Duke
of Argyle,* ‘have described themselves as never tired
of watching its glorious and triumphant motion:

* ©The Reign of Law.’
Birds of the Air. 329

6“ Tranquil its spirit seemed, and floated slow;
Even in its very motion there was rest.”

‘Rest—where there is nothing else at rest in the
tremendous turmoil of its own stormy seas! Some-
times for a whole hour together this splendid bird will
sail or wheel round a ship in every possible variety of
direction without requiring to give a single stroke to its
pinions—those long slender wings, some fifteen feet
across from one extreme tip to the other. Such wings
are peculiarly adapted for flying long and far, for floating
at ease, and for overcoming the force of ocean-gales.’

Short-winged birds may advance fast, but they can-
not keep it up long, and floating on the air at ease is
out of their power.

When one thinks of Bird-Life in general, with all
its infinite shades of variety, the difficulty is to know
what to select for a few paragraphs on the subject. Bird-
kinds count by thousands and tens of thousands. Bird-
ways are as varied as human ways, not to say more so.

Taking Britain alone, birds pass downward in
gradual progression from the great eagle to the little
wren—numberless multitudes lying between. Taking
the world generally, the list, already so long, is tre-
mendously extended. For then ‘the range extends
from the huge ungainly ostrich to the tiny brilliant
humming-bird.

Where the more temperate climates of Earth are
found, each season* brings its own peculiar phase of
bird-life. This is markedly the case in England.

WINTER means commonly for birds an uncertain
wandering existence. They have to be very much ‘on
the tramp’ in search of food, except where they find

* “Among the Birds,’ by C. Dixon.
330 The Ocean of Air.

' attainable stores, or better still, kind human friends to
scatter crumbs day by day.

A long and hard frost tells severely upon the Birds
of the Air. Heavy snowstorms break through all their
usual habits, slaying large numbers, driving oceanic
birds inland, making shy ones tame and wild ones
almost domestic. Sea-gulls have been seen as high up
the Thames as Westminster Bridge, and even the dis-
tant dignity of the eagle is not always proof against
intense cold.

Some years ago, when I was with friends in Scot-
land, we came across a worthy Highland cottager,
living in a lonely spot not far from the Dee. She
described a long and bitter winter in terse terms,
and told how the very eagles had come down from
their: mountain retreats to hover round her cottage,
looking out for scraps of food.

River-haunting birds, whose food lies under water,
are among the worst off at such times. A sheet of ice
means starvation to many a lovely blue and green king-
fisher, sitting forlornly among the ice-clothed bushes,
vainly watching the hard surface which his beak cannot
penetrate.

Coming Sprinc works a wonderful change in the
world of Bird-Life. Spring is the time for all their
pretty love-making and mating, for any amount of
singing and quarrelling, for diligent nest-building and
egg-laying.. The rooks are hard at work: and the
sound of the cuckoo is heard; while the woods and
meadows ring with the wild sweet voices of thrush
and blackbird, linnet and robin. For of course: the
robin sings still, as he has bravely done all through
the winter cold. Only he is now part of a. general
chorus, not one among a very few solos.
Birds of the Air. 331

Then, too, the winter absentees begin to return.
The tiny ‘willow-wren steals silently back from his
winter retreat in Africa,’ and the swallows and
martins troop homeward by no means silently. Some
repair their old nests, and some build new ones. The
nests are various in kind as the builders; delicately-
finished constructions here, rough piles of sticks and
moss there.

SUMMER comes next—a time of calm happiness to
birds, only broken in upon by the inevitable trials of
domestic life, by stormy weather, and by the attacks
of the strong upon the weak. In certain other lands
little birds have been almost exterminated; but in
England they still spend in the main joyous summer
days, and insects have not yet a chance of over-
whelming the farmers for lack of birds to feed on them.

Birds’ voices wane as summer goes on, and little
families are launched in life, and arrangements. for
autumn gradually begin to take shape. The migratory
birds draw more together, as if disposed to talk over
their plans.

AUTUMN is the time for change, except with
those little constant birds who cling faithfully to
home through all, taking their chance of ice and snow
and bitter blast. Both late summer and early autumn
are a quiet, not to say a depressed, time in the Bird-
world. For moulting takes place, and singing voices
have vanished, and bird-powers generally are at a
somewhat low ebb.

When moulting is over, the robin gets back his
voice, as also do the wren, the skylark, and a few
others. But the autumn singing, however sweet, never
approaches the outburst of sound which belongs ‘to
spring.
332 The Ocean of Air.

Even home-staying birds are very busy,: seeking
winter retreats; and those who have a long aerial
voyage ahead are in all the flurry of a speedy depar-
ture. Many people can never travel without a certain
amount of preliminary fuss, and birds seem to follow
the same rule. After all—no wonder! A perilous
route lies before them.

‘The migration of birds is beset with many dangers
and difficulties. Birds often lose their ways: a con-
trary wind ora spell of dark cloudy weather appears
to disorganize their movements, and ‘like mariners
without a compass, they are at a loss which direction
to take.’*

The wonder seems to be, not that they often lose
their way through the trackless depths of the Air-
Ocean, but that they ever find it! How far they
journey by instinct, and how far the younger birds are
guided by the knowledge of older ones who have
travelled the same route before, who shall declare with
certainty? ,

Strange sights are often witnessed in autumn, by
the men of a lighthouse, after dark. In clear weather,
it is said, the birds usually steer clear of the light; but
when the air is thick with rain or fog they draw near
in multitudes. On such occasions, thousands may be
seen to pass: ducks and geese, swallows and wrens,
herons and swans, starlings and thrushes, finches and
larks, these and others, intermingled with birds of prey
forgetting to prey, while their usual victims forget to
flee from them. All alike are bewildered, frightened,
hurrying to and fro, wandering hither and thither,
not knowing whither to turn. Too many dash out
their brains against the strong glass of the lighthouse,

* C. Dixon.
Birds of the Air. . 333

and so never reach the southern lands, whither they
are bound.

Yet out of all the perils which they meet, great
numbers do arrive safely ;.and great numbers do come
back again to’us next spring, for fresh singing, mating,
nest-building, and family-rearing.

It has been lately asserted that no less than ninety
varieties of birds may be seen in London alone, not
counting escaped foreigners from cages. Rookeries
still exist there, and even owls are to be found within
Metropolitan limits. Jackdaws are tolerably common ;
the blackbird and the thrush are not absolute strangers;
swallows fly to and fro, though they will not build in
the great city ; and while the redbreast eschews London
streets, it still clings to the outskirts.

The London birds par excellence are sparrows and
pigeons. Before the days of electric telegraphs, the
pigeon was a useful news-carrier. One well trained will
fly at the rate of a mile a minute, keeping up the speed
persistently for one hundred miles.

Marvellous as this sounds, it is exceeded by other
birds. A rook going at full speed beats the fastest
express train ever made by man: for he can hasten
through the Ocean of Air at the rate of one hundred
miles an hour.

The length of time that some birds can fly, without
needing to alight, is extraordinary. Seagulls have been
known to accompany steamers all across the Atlantic
Ocean, careless of the roughest head-winds, floating
about with most absolute ease and apparent absence of
exertion, scarcely seeming ever to rest. They are said
to sleep upon the wing, tucking away their heads like a
canary on its perch, rocked on the bosom of ‘the wild
334 The Ocean of Air.

winds, flying in sleep as we all breathe in sleep, uncon-
sciously and mechanically.

From the wide world of Bird-life we might pass
onward still, through multitudes of ‘small and great
beasts,’ till another wide gap is reached—that which
divides brute-life from human life ; that which separates
the most highly-developed intelligence of lower animals
from the wonderful brain and spirit powers of Man.

Even Man, however, head as he is of the animal
kingdom, unutterably superior to the noblest of his
subjects in possibilities, if not always in action—even
he in this life can but creep about, on or near the
bottom of the Aerial Ocean. Even he can but watch
from thence, with curious eyes, the wonders of that
Ocean, searching into its make, its movements, its
governing laws, its conflicting forces, its countless
forms of Life.
INDEX.

AETHER, 51, 277
Affinities, 287

Air,
a
”

”
Air-

a bad conductor, 250

absence of, 15

a fluid, 6, 25, 190

circulation of, 18, 60, 165, 171-
182, 260

colour of, 4, 20, 280, 301

currents of, 137, 145, 165-180

density of, 7-14, 119

diurnal revolution of, 40, 177

elasticity of, 25, 43, 326

extent of, 7

make of, 6, 33-7, 55,113

molecules of, 291-2

movements of, 18, 35, 165-189,
212-238

need of, 79-84, 90-93

particles of, 3, 30, 48, 119, 289,
291, 311

pressure of, 8, 30-32, 119, 213

purification of, 108

resistance of, 43, 44-50, 250-2,
326

a substance, I, 23-30

temperature of, 3, 4, 129-134,
170, 211, 213

transparency of, 21, 69

viscosity of, 43

water in, 113-136, 250

weight of, 3, 4, 7; 23) 30-32,
119, 263

work of, 19, 69, 198, 314

‘Wave, 306

Albatross, 328

Amber, 245-6
American Tornado, 235
Ammonia, 36-7, 292

Anti-cyclones, 215, 225-6

Anti-trades, 173-4, 197, 307

Arctic Cold, 209

Arteries, 98

Athermanous,’ 266

Atmosphere, see Air

Atmospheres, two, 113-4, 120

Atmospheric Circulation, see Az,
Circulation of

Atmospheric Distilling Apparatus,
196-8

Atmospheric Pumping Engine, 19

Atoms, 284-295, 299

Attraction, see Gravitation

Aurora Borealis, 256-8

Australian Desert, 207

Avalanches, 167

BACTERIA, 311
Balloons and Balloon Ascents, 10-
14, 39, 149-152
Barometer, 213, 215, 219, 225, 232
Beetle, Water, 17
Bird-Life, 329
Bird Seasons, 329-333
Birds, 325-334
»» Migration of, 332
Black Hole of Calcutta, 82
3, Rain, 305
Blizzard, 157, 310
Blood, Circulation of, 60, 97-100, 180
Blood-rain, 304
Bodily exertion, 91
Bottled-up Sunlight, 107
Brain-work, 91
Breath of Life, 97, 316
Breathing, 6, 80, 89-101, 107-8
a9 of Beetle, 17
336

Breathing of Plants, 107-8
os of Spider, 18
s3 -tubes of Insects, 317-8
$5 of Whale, 17
Breeze, Land, 169
5 Sea, 169
Bright Rays, 268
Butterflies, 323
Burning, 62-9, 89-101

CaucuTTa, BLack HOLE oF, 82
Calliope, Escape of, 237
Calms, Cancer, 175, 179
3, Capricorn, 175, 179
>, Equatorial, 173, 196
Caloric, 260
Campagna di Roma, 313
Camphor, 123
Cannon-ball, 48
Capacity for Heat, see Specific Heat
Carbon, 67, 70-88, 96-109, 138
» Circulation of, 74
»> -points in flame, 69
Carbonic Acid, 36, 68, 74-109
Chain of Causation, 198
Charcoal, 71, 76
Charge of Electricity, 249
Chemical Combination, 33-5, 56, 61,
63, 68, 95-100, 285-7
Chemical Rays, 279
Cherrapongee, rainfall, 155
Chesil Beach, 184
Chimborazo, 9
Circulation of Air, see Air, Circula-
tion of
53 of Blood, 60, 97, 180
os of Carbon, 74
3, of Dust, 300
% of Oxygen, 60
a7 of Water, see Water, Cir-
culation of
Cirrus, 147
Climate, 203-211
»» lines, see Zsotherues
» Zones of, 204
Climbing, 8, 9
- Clouds, 12, 143-156
>, Cirrus, 147
s» Cumulus, 147
” Ice, 144
» Mist, 144, 146
» Nimbus, 148



The Ocean of Air.

Clouds, Rain, see Nimbus
»» Ribbon, 145
», Stratus, 147
Coal, 67-9, 725 85
Coal-gas, 79, 84-5
Cohesion, 27, 288
Cold, Arctic, 209
» Canadian, 204
» Siberian, 203-4
Collision of Steamers in fog, 137
Collisions of Molecules, 30-32, 291-2
Colour of Air, 4, 20, 280, 301
Colours, 278-282
Combination, see Chemical Comlt-
nation
Combustion, 62-9, 72, 89-101, 127
Compound Substances, 34, 71
ond enssticns 129-134, 143-8, 195-7,
22
Conductors, 248, 252
Conduction of Heat, 266
Conservatory, 268
Coxwell, 10-14
Crystallization, 116, 156, 263
Cumulus, 147
Currents, Ocean, 126, 190-3
Cyclones, 215, 218, 222-4, 230-8
Cyclonic Waves, 188

Dark Rays, 268
Dead-leaf butterfly, 324
Decay, 87
Density of Air, 7, 9, 119
De Saussure, 9
Desert Heat, 207, 309
Dew, 135-142

1» “point, 140
Diamond, 73
Diathermanous, 266
‘ Differences of Potential,’ 247
Diffusion of Heat, 266
Digestion of Plants, 108
Disaster, Tay Bridge, 228
Discharge of Electricity, 249
Dispersion of Light, 280
Disruptive Discharge, 252
Distilling Apparatus, Atmospheric,

196-8
Doldrums, 173
Dragon- flies, 320
Draughts, 168
Dust, 36, 139, 257, 299-316
Index.

Dust, circulation of, 300
» falls of, 304 :
1 Java, 306
» kinds of, 301
», storms, 308 -

EARTH, MOTIONS OF, 38-9

Echo, causes of, 271-2, 275

Eddies of Air, 217, 221-9
Eddystone Lighthouse destroyed,

227
Elasticity of Air, see Azr, Zlasticity

a
Electricity, 154, 241, 245-258
a Force, 241, 260
Electric charge, 249
i currents, 249, 251
», lighting, 256
” spark, 251, 253
Electrics, 246, 248
Elementary Substances, 34, 5), 70,
286
Equatorial Calm-Belt, 173, 196
Evaporation, 121-9, 132, 143-152,
22

35 of Solids, 123
Everest, Mount, 8
Extent of Air, 7

FERMENTATION, 77
Fijian Climate, 210
Fireballs, 242
Flame, 65, 66, 69
Flash of lightning, duration of,
Flight of Birds, 325-9, 333
» of Insects, 321-2
Fogs, 135-9
Food, 90-2, 103
Forces of Nature, 25-27, 241,
260, 286, 295
Forked Lightning, 239
Franklin, 253
Friction, 47
Frost, 116, 154, 263
Frozen Clouds, 144
», Waterfalls, 161

240

255,

Gas, 79, 84-6

»5 explosions, 85

» molecules, 291

gases, 25, 29, 56-61, 75-88, 115,
117, 205, 291, 293



337

Galileo, 24

Germs, 311-315

Gibraltar, Straits of, 125
Glaciers, 198

Glaisher, 10-14, 149, 160
Globular Lightning, 242

Gold, 34

Graphite, 72

Gravitation, 7, 24, 29, 49, 255, 26
Great Storm of 1703, 227
Ground Fog Clouds, see Stratus
Gulf Stream, 22, 192

HAIL, 159-162
9» *stones, 160-1
3, storm of 1843, 160
Halos, 145
Hardraw Force, 162
Health, 80, 89-92, 108
Hearing, 274
Heat, 259-269, 285, 293-4
» a force, 26, 115, 127, 131
x» Desert-, 207, 309
» given off, 61, 63, 69, 95-6, 127
» Indian, 204
1) “rays, 266-9
» transformed into Work,. 261,
26
Himalayas, 5, 8
Hoar-frost, 141
Horse- Latitudes, 175
Humboldt, 9
Hurricanes, 41, 182-3, 220, 2308,
302
Hydrogen, 23, 34, 65, 67, 95
7 molecules, 286

IcE, 25
» clouds, 144
» crystals, 116, 156, 263
»» Molecules, 293
needles, 116, 144, 263
Ignition, 66
Incandescence, 66
Indian climate, 204
Infectious germs, 312
Inertia, 46, 49
Insects, 317-324
Insulators, 249
Tron, 34, 115
» rust, 63
Isobars, 214-19

to
lo
338
Isotherms, 205, 214

JET, 245
Joyeuse, Rainfall, 155

KHAMSEEN, 308
Kilauea, 86
Krakatoa Dust, 305

LAND-BREEZE, 169
Latitude, Lines of, 205
Laughing Gas, 55
Laws of Nature, 24, 27, 295
Leaves, 103-9
- Level of Water, 190
Life, 89-101, 103, 105, 311-15
» Breath of, 97, 316
Light, 20, 21, 268, 276-82
x, Rays of, 21, 121, 206,
266-270, 276-282
x» scale, 269, 273
3, speed of, 276
3» “waves, 276-8
Lightning, 239-42
Liquids, 25, 29, 115, 117, 132, 265,
290, 293
Locusts, 319, 322
Lodestone, 253
London Fogs, 138
Lungs, 99

MAGNETIC MERIDIAN, 256
3 Poles, 254

Magnetism, 245, 253-6

Magnets, 253, 254

Malaria, 312-14

Manganese-dust, 258

March-dust, 299

Mares’ Tails, see Cirrus

Mars, 25

Massowah, 204

Matter, Universe of, 68

May-flies, 320

Mediterranean Sea, 125

Blue of, 280

Meteoric dust, 257-8, 301

Miasma, 312-14

Microphone, 274

Migration of Birds, 332

Mist-Clouds, 144, 146

Mists, 131, 135-142



| Oxygen, 34-55 55-61, 64,

The Ocean of Air. :

Moisture, 113-15,
145-9, 196-9, 206

Molecules, 284-95

” battery of, 31

Monsoons, 182-4, 232

Mont Blanc, 9

Moon, green and blue, 305

Mosquitces, 318

Motes, 300

Motion, 44-51, 290-5

Motions of the Earth, 38

Mountain Climbing, 8, 9

Movements of Atoms and Mole-
cules, 290-5

Mount Everest, 8

Musical sounds, 275-6

121-5, 132-40

NATURE, Forces oF, see Forces of

Nature
93 Laws of, see Laws

Nature

Negative Electricity, 246, 251

Nimbus Clouds, 148

Nitre, 55

Nitrogen, 35, 55-75 95

Nodules, 258

Non-electrics, 248

North Sea, 185-7

OCEAN, BLUE OF, 280
+» currents, 126, 190-3
o evaporation of, 126
waves, 184-9, 272
Owl Butterfly, 323
Oxides, 61, 63
Oxidation, 61, 63, 96, 106
75-101,
106-9
o> Circulation of, 60

PAMPEROS, 230, 232
Paper, 266
Particles, 26, 28, 31, 41, 67, 69, 116,
146, 262-5, 283-95
mn of Air, see Azr
i of Water, see Water
Pigeon, speed of, 333
Plant-life, 102-9
Plants, breathing of, 107
+ digestion of, 108
» work of, 106, 109
Plumbago, 72, 74
Index.

Positive Electricity, 246, 251
Power of Sun, see Suz
Precipitation, 134

Pressure of Air, 8, 30-2, 119, 213
Primary Colours, 279

Prism, 279-81

Pumping Engine, Atmospheric, 19
Purification of Air, 108°

RADIANT HEAT, 267, 269
Radiation, 121-2, 135, 140,
268, 271
Rain, 153-6, 195, 218-226
>» ‘bow, 281
3» causes of, 154
», cloud, see Mimbus
x drops, 154
>» fall, 155
1 gauge, £55
Rainy Season, 183
Rate of Winds, 231
Rays of Heat and Light, 21, 121,
206, 266, 270, 276-282
Reasons and Causes, 49, 295
Rechman, 253
Red Rain, 304
Red Snow, 304
Reflection of light, 5, 21, 281
Refraction of light, 145, 280
Repulsion, 28, 254
Resistance of Air, see dir
Rest, 44, 49
Ribbon Clouds, 145
Rivers, 192, 194
‘Roaring Forties,’ 176, 179
Rook, speed of, 333

225, |



SAHARA SAND, 304
Salt, 302
Sap, 104
Saturation, 123, 129-132, 140, 197
Scent, 292
Sea-breeze, 169
Sea-gulls, 328, 330, 333
Sheet Lightning, 239
Siberian climate, 203-4
Simoom, 309
Simple Substances, 34, 59, 70, 286
Sirocco, 309
Smoke, 79, 13&
Snow, 156-9
» Makes, 156

339
Solar System, 294
Solids, 25, 29, 115, 117, 265, 289-90,

293
Soot, 64, 67
Sound, 20, 270-6

‘ -scale, 273-6
” speed of, 271
is waves of, 270-5

Specific Heat of Water, see Water,
Specific Heat

Speed of Birds, 333

Spider, 18, 317

Spores, 311

Squalls, 226

Steamers in fog, Collision of, 137

Steam, 114, I17, 127, 131, 263-5,

293, 293

+» engine, 261

Storms, 157-161, 185-9, 222-227,
233-8

St. Paul’s Cathedral, 168

Straits of Gibraltar, 125

Stratus Clouds, 147

Sugar, 71

Sulphur, 33

Summer Lightning, 239, 240

Sun, Power of, 107, 127, 196-8, 206

Sunsets of 1883, 305

Sunset hues, causes of, 280

Sunlight, 107

Tay BripGeE DISASTER, 228
Temperature, 259-262
x of Air, see Air

Thermometer, 204, 211-12, 214, 259
Thunder, 251-2, 271

7 storm of 1843, 160

” -storms, 226, 279-242
Tornado, American, 235
Torricelli, 24
Trade-winds, 171-182
Transparency of Air, 21, 69
Tropical Vapour, 196-7
Trough of Cyclone, 224
Two Oceans, 190
Typhoon, 230, 232, 234

UNDULATIONS, see Waves
Vapour, see Water-vapour

Vegetation, 87, 102-9, 112
Veins 98
340

Vibrations, see Waves
Viscosity of Air, 43
Volcanoes, 86, 306
Volcanic Dust, 307
Vortex of Air, 224

WATER BEETLE, 17
Water, circle of changes in, 194, 198

” circulation of, 19, 60, 190-
199

a condensation of, 129-134

9 -dust, 131

” evaporation of, 121-8

% -falls, frozen, 161

i freezing of, 116, 263-5
3 in Air, 113-134, 250
os keeping its level, 190

» make of, 34
a3 particles of, 26, 114, 146,
283-6

- precipitation of, 135-156
7 specific heat of, 136, 142,
169, 192, 207, 255, 264-6
+ -spider, 1
three forms of, 25, 29, 115
116-7, 265, 292

The Ocean of Arr.

Water-vapour, 36, I13, 121-134,
146, 197, 206, 250

Walking-stick Insect, 324
Waves, 184-9, 270-9

a Cyclonic, 188
Weather, 212-220

» -lines, see Lsobars
7 prognostics, 221-3
Ww eight of Air, see Azr, weight of
Werchojansk, 204
Whales, 16-7
Whirlwinds, 232-8
Whymper, 9
Winds, 40-3, 124, 165-189, 203, 207
225, 230-8, 291. 307

»» Causes of, 167-171

» force of, 184-189, 236-7

+» nature of, 166
Windmills, 165
Wings, 321, 326-9, 333
Winters, severe, 157
Woolpack, Clouds, see Czmzelus

Zigzag Lightning,
ning
Zones of Climate, 204

see Forked Light-

THE ENDL,

SILLING AND SONS, PRINTERS, GUILDFORD.

Rat

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