The Baldwin Library
[ /T> rUniversity
Nlfln^ d I
THE MER DE GLACE.
GEOLOGY FOR BEGINNERS
AUTHOR OF 'SUN, MOON, AND STARS,' ETC.
WLift sixteen *sUtafraionse
'Of old hast Thou laid the Foundation of the Earth.'-PsA. cil. 25
SEELEY AND CO. LIMITED
38 GREAT RUSSELL STREET
THE very warm and hearty reception accorded to my
little book on Astronomy, has been my best en-
couragement in entering upon the domain of the
sister science, Geology.
This companion-volume to 'Sun, Moon, and Stars'
is written upon much the same plan, and is intended
for the same class of readers-for Beginners of all
kinds, whether poor or rich, whether boys, girls, or
My object in writing it has been not so much to
supply a certain amount of technical knowledge,-for
this may be easily obtained from ordinary class-
books,-as to open the eyes of others to the hidden
wonders and possibilities of enjoyment which lie
folded in this little-studied branch of science.
Geology is counted by many to be a dull subject.
But if it has its dry bones, it has also its forms of
poetic beauty, its scenes of loveliness, its chords of
Geology is counted by others to be a dangerous
subject. But if so, the danger lies in ourselves, not in
Geology. Man's haste in decision, and his readiness
to put faith in unproved theories, may lead him
astray. The study of God's truths, if rightly under-
taken, cannot cause his feet to wander.
Geology speaks to us, as surely as the Bible itself
speaks to us, of the Creator and His ways, albeit in
terms more ambiguous, in language more easily mis-
understood. The one is His Word, the other is His
Handiwork. That the one should contradict the
other is not possible. That the one and the other
should contain mysteries past our power to fathom, is
only what we might expect from the Word and the
Handiwork of an Infinite God.
I have merely to state, in conclusion, that neither
time nor pains have been spared in the endeavour to
ensure accuracy as well as interest. The leading Geo-
logical writers of England and of America have been
my authorities. Thanks, lastly, are due for the kind
and able criticisms of competent friends, who have
generously given time and thought to the examina-
tion of my proof-sheets.
WORTON HOUSE, EASTBOURNE,
HOW TO READ THE RECORD.
CHAPTER R PAGE
I. WHAT THE EARTH'S CRUST IS MADE OF I
II. WATER-BUILT ROCKS IO
III. FOSSILS IN THE ROCKS 20
IV. FIRE-BUILT ROCKS 32
V. WHAT ROCKS ARE MADE OF 42
VI. ROCK-LAYERS 53
VII. ROCK-BENDINGS 61
VIII. ICE-WORK 7c
IX. THE TWO BOOKS 83
A STORY OF OLDEN DAYS.
X. TWO KINGDOMS 9
XI. EARLIEST AGES 101
XII. THE AGE OF LOWER ANIMALS 107
XIII. THE AGE OF FISHES 118
XIV. THE AGE OF COAL 125
XV. MORE ABOUT THE AGE OF COAL 135
XVI. THE AGE OF REPTILES 143
XVII. THE AGE OF CHALK
XVIII. THE AGE OF MAMMALS -
XIX. MORE ABOUT THE AGE OF
XX. THE AGE OF ICE -
XXI. THE AGE OF MAN
XXII. THE TWO RECORDS
THE PAST IN THE LIGHT OF THE PRESENT.
XXIII. RIVERS -
XXIV. WATERS -
XXVI. GLACIERS -
XXIX. HOT SPRINGS
XXXI. STALAC ITE
TABLE OF SUBJECTS.
CHAP. I.-What the Earth is made of.-Meaning of Geology.
-The Earth's Crust.-What is meant by a 'theory.'-
Different kinds of Rock.-The Volume of Geology 3-9
CHAP. II.-Stratified and Unstratified Rocks.--Crystallization.
What is meant by Stratified Rocks.-Changes in the Earth-
crust.-Crumbling away of cliffs.-Work of torrents.-
Sediment and detritus.-Sedimentary Rocks 1o- 19
CHAP. III.-Building up of Stratified Rocks.-Chalk cliffs and
old sea-beaches.- Land-sinkings.-Past ages of preparation.
-Aqueous Rocks.-Fossiliferous Rocks.-Different kinds
of fossils.-Fossils on mountain-tops, and how they came
there.-Arrangement of Strata.-Disturbances in the Earth-
CHAP. IV.-Volcanic Rocks, Plutonic Rocks, and Metamorphic
Rocks.-Aqueous and Igneous Rocks.-Primary, Secon-
dary, and Transition Rocks.-Building of the Crust.-
Powers of Nature.-Under-ground heat.-Volcanic erup-
tions.-Earthquakes.-Theories of explanation, Fire and
Water .- 32-41
viii Table of Subjects.
CHAP. V.-Flint, Clay, and Lime Rocks.-What Rocks are
made of.-Rhizopods.-Chalk Cliffs.-Limestone.-Fossils
in Rocks.-Diatoms.-Mountain Meal.-Coal 42-52
CHAP. VI.-Rock-building in past ages.-Arrangement of
Strata.-Different kinds of fossils in different Strata.-
Classification of Strata.-TABLE OF STRATA 53-60
CHAP. VII.-Thickness of Stratified Rocks.- Chain of records.
-Difficulty of reading the record.-' Stratum' and' layer.'-
CHAP. VIII.-Fossil rain-prints and ripple-marks.-Stones
scratched and scored.-Scotch 'till.'-Boulder- clay or
drift.- Erratics.-Diluvial Soil.-Glaciers.-Moraines.-
Icebergs.-Probable explanation of scratched stones.-
Glacial Age 70-82
CHAP. IX.-World-history before the time of Adam.-Past
Ages.-Days of Creation.-The two great Books.-How
to read them.-Preparation of the Earth for Man 83-88
CHAP. X.-The Animal and Vegetable Kingdoms.-Divisions
in Nature.-Classification.-Animals, plants, and rocks.-
Life.-.'Organs.'-Sub-kingdoms and classes.-TABLE OF
THE ANIMAL KINGDOM.-TABLE OF THE VEGETABLE
CHAP. XI.-Creation of the world.-Stages in existence of
heavenly bodies.-Probable stages in preparation of t.e
earth.-Earliest-known rocks.-Earth in those days
Table of Subjects. ix
CHAP. XII.-Primary or 'Ancient Animal' Rocks.-Three
great Ages.-Age of Lower Animals or of Limestone-build-
ing.-Seas and continents.-Coral-making.-Disturbances.
-Sea-weeds and sea-creatures of Silurian Days.-Trilo-
bites.-The first Fishes 107-117
CHAP. XIII.-Age of Fishes.-New Red Sandstone.-Coral.-
Flowerless plants. Forests.- Insects. Fish-fossils. -
Trilobites and lobsters 18-124
CHAP. XIV.-Day of Coal-preparation.-Description of forest-
scene in Coal-Age.-First reptiles.-Rising and sinking of
the ground.-Coal-seams.-Sigillaria and Stigmaria.-Tree-
trunks in mines 125-134
CHAP. XV.-Coal-beds in South Wales.-Alternate layers of
rock.-Climate in Coal-Age.-Forests.-Ferns.-Trees.-
Vegetable fossils in coal.--Sigillaria.-Amphibians.-First
True Reptiles.-Mountains upheaved.-End of Primary
Period -- 135-142
CHAP. XVI.-Middle-Life Period begun.-Reptiles.-Gigantic
crocodiles, lizards, winged reptiles, water reptiles, etc.-
Saurians.-Tracks of Amphibians and Reptiles.-Coal-pre-
First Mammals.-Plants 143-153
CHAP. XVII.-Chalk-building.-Great Chalk formation.-Rep-
tiles.-Animalcules.-Nature of mud at bottom of Atlantic
Ocean.-Rhizopods and Diatoms.-Chalk and flint.-Time
occupied in building.- Chalk-formation in America.-
Geography of the Age.-Great change in plants.-Flower-
ing plants.-Reptiles, birds, and ammonites.-Close of
Chalk-Age and Secondary Period.-Widespread destruction
of life.-Possible Ice-action 154-168
x Table of Subjects.
CHAP. XVIII.-New-Life Period begun.-Sea and freshwater
shells.-Third-Period rocks and fossils.-Nummulites. -
Upheaval of mountains.-Climate.-Plants.-London and
Paris Basins.-British Isles 169-174
CHAP. XIX.-Possible Icebergs.-Signs of cold.-Mammals.-
Ammonites, nummulites and corals.-Vegetation.-Animals
in England and France.-Ancient quadrupeds and whales.
-European plants and trees -175-182
CHAP. XX.-Post-Tertiary Age.-Great Ice-Age.-Drift or Till.
-Periods and Ages.-Glacier Theory.-Huge quadrupeds.
-Time of Floods.-Mammoths and mastodons 183-194
CHAP. XXI.-Human relics.-Stone-Age, Bronze-Age, and
Iron-Age.-History of Nations.-Human remains in caves.
-Supposed second Ice-Age 195-202
CHAP. XXII.-The Divine Architect.-The Bible-Record of
Creation.- Theories of explanation.-Water and Fire.-
A caution.-The uniformity theory.-Periods and Ages.-
TABLE OF GEOLOGICAL AGES 203-216
CHAP. XXIII.-Work of running water.-Wearing away of
rock.-Earl of Mar's Punch-bowl.-Pot-holes.-' Glacier-
holes' at Lucerne.--Reuss in Pass of St. Gothard.-Land-
slip on the Vispbach.--River Simeto.-Niagara.-Two
beds of a river 219-227
CHAP. XXIV.-Rains.-Tropical rainfalls.-Artesian wells.-
Wear of cliffs round Britain.--Shetland Islands.-Bell-Rock
CHAP. XXV.-Sand-bars.-Mud-banks.-River Deltas-Lake
and Ocean Deltas-Lake of Geneva.-The Rhone.-The Po
and Adige.-The Nile.-The Ganges and Brahmapootra.-
Mississippi.-Bay of Fundy mud-flats 236-245
Table of Subjects. xi
CHAP. XXVI.-A glacier.-Movements of a glacier.-Icebergs.
-Mont Blanc glaciers.-The Mer de Glace.-Greenland
glaciers.- Moraines. Spitzbergen icebergs. -Greenland
CHAP. XXVII.-A Volcano.-A crater.-A cone.-Active,
Dormant, and Extinct Volcanoes.-Different kinds of erup-
tions.-Volcanoes of the Andes.-Mexican volcanoes.-
Icelandic volcano. Etna. Galongoon. Vesuvius. -
Hawaiian volcanoes.-Monte Nuovo.-Lakes of fire.-
Fountains of fire 255-269
CHAP. XXVIII.-Cause of Earthquakes.-New Zealand earth-
quakes.-A fault.-Earthquake in Chili.-Earthquake in
Cutch.-Caraccas earthquake.-Calabrian earthquake.-
Waves and cracks.-Earthquake of Lisbon.-Earthquake
in Jamaica.-General effects of earthquakes 270-280
CHAP. XXIX. -Slow movements of earth-crust.-Rising of land
in Sweden.-Sinking of land in Greenland,-Floor of
Pacific Ocean supposed to sink.-Temple of Jupiter Serapis
-Nearness of volcanoes to ocean.-Power of steam.-Hot
CHAP. XXX.-The coral-Polyp.-Kinds of Coral.-Deep-sea
corals.-Reef-building corals.-Work done by waves.-
Formation of an Island. -Atolls.--Lagoons. -Maldive
Theory of explanation.-Sinking sea-bottom.-Speed of
CHAP. XXXI.-Peat-mosses.-Speed of Peat-formation.-Land-
slips.-Slide on the Rossberg.-Stalactite and Stalagmite
caves. Digging out of passages by water. Cheddar
Caverns.-Animal remains in caves.-How long there ?-
Speed of Stalagmite formation.-Need for caution.-Much
that cannot yet be understood in Geology 305-313
LIST OF ILLUSTRATIONS.
MER DE GLACE .. Frontispiece
CHART OF STRATA 62
MAGNIFIED SPECK OF EARTH, AND SCRATCHED STONES 74
FOREST OF THE CARBONIFEROUS AGE
FERN FOSSILS IN COAL
SKELETON OF MEGATHERIUM
ANIMALS OF THE TERTIARY AGE
FLOATING ICEBERG .
EARTHQUAKE AT LISBON
HOW TO READ THE RECORD.
WHAT.. THE' EARTH'S CRUS' 1IS: MADE: iOF;
'Stand still and consider the wondrous works, of God.'-Jox
WHAT is the earth made of-this round -earth upon
which we human beings live and move.?-
A question more-easily asked, than, answered, as
regards a very large portion of it. For the earth is a
huge ball nearly, eight -thousand, miles, in..diameter,
and we who dwell on the outside. have no. means of
getting down more than a very little way below the
surface. So.it is quite impossible for us:to speak posi-
tively as to the inside of the earth, and what it is made
of. Some people believe the earth's inside to be hard
and solid, while others believe it to be- one enormous
lake or. furnace of fiery melted rock. But, nobody
4 What the Earth's Crust is Made of.
If we break up the word GEOLOGY, we find that it
is made out of two Greek words, ge, the earth, and
logos, a word or discourse. The meaning of' geology'
is simply a word, or a discourse, or teaching, about the
earth. More strictly, it is not teaching about the
whole earth, but only about the crust of the earth.
This outside crust has been reckoned to be of many
different thicknesses. One man will say it is ten miles
thick, and another will rate it at four hundred miles.
So far as regards man's knowledge of it, gained from
mining, from boring, from examination of rocks, and
from reasoning out all that may be learnt by these
observations, we shall allow an ample margin if we
count the field of geology to extend some twenty miles
downwards from the highest mountain-tops. Beyond
this we find ourselves in a land of darkness and con-
Twenty miles is only one four-hundredth part of the
earth's diameter-a mere thin shell over a massive
globe. If the earth were brought down in size to an
ordinary large school globe, a piece of rough brown
paper covering it might well represent the thickness of
this earth-crust, with which the science of geology has
to do. And the whole of the globe, this earth of ours,
is but one tiny planet in the great Solar System.
And the centre of that Solar System, the blazing
What the Earth's Crust is Made of. 5
sun, though equal in size to more than a million
earths, is yet himself but one star amid millions of
twinkling stars, scattered broadcast through the uni-
verse. So it would seem at first sight that the field
of geology is a small field compared with that of
But as we go on we shall find that the lesser things
of God are, in their way, as great as those things which
at first sight may seem the mightier. We shall find
prospects of wonder and power, of mystery and
beauty, unfolding before our eyes. Wrapped up in
the crust of this earth are marvellous tokens of the
goodness and greatness of God, and strange histories
of olden days are written in her stones.
So it is distinctly with the .question of the earth's
crust that we are now concerned-how that crust was
formed, how it was changed and modified by various
influences, how it was gradually built up into its pre-
For the earth's crust was not always such as it is
'In the beginning God made the earth'-but He
did not make it then and at once complete. There was
a time when man's foot had never pressed her soil.
There was a time, farther back, when no wild beasts
roved through her forests and no cattle browsed upon
6 What the Eartk's Crust is Made of.
her hills. There was a.time, yet fartherback, when no
fishes swam in ,her wide waters.. There was a time,
still farther back, when no. forests clothed her moun-
tains: or lined her valleys. There was -a time, yet
farther removed from .the-present, when no mountains
towered heavenward, and no valleys had been scooped
out between them. There was a timeistill more dis-
tant, when no continents or islands had risen out of
the mighty and dark ocean, and in all the dreary waste
of waters life was a thing unknown.
For stage by stage, God was slowly preparing this
earth-crust to be the abode of man, working calmly
and deliberately, as God does work, with none of the
feverish haste and restless impatience of man. What
are countless ages in their flight to Him who is the
King of Eternity?
But now we come back to the, question with w.'h
we began, the question as to what this earth i_
With regard to the great bulk of the globe little
can be said. Very probably it is formed through and
through of the same materials as the crust. This we
do not know. Neither can we tell, even if it be so
formed, whether the said materials are solid and cold
like the outside crust, or whether they are liquid with
'What the Earlh's Crust-is-Made of y
heat. The belief has been long and widely held that
the whole inside of the earth:is one vast lake or fur-
nace of melted 'fiery-hot material, with only a thin
cooled crust covering it. Some in the present day are
inclined to question this, and hold rather that the
earth is solid and cold throughout, though with large
lakes of liquid fire here and there, under or in her
crust, from which our volcanoes are fed. Either
opinion or both opinions may be mistaken.
It will be found, as we go on, that a great many
opposite opinions are held on many questions in geo-
logy, and that a great many theories are started which
have very little real foundation. A 'theory' is possible
explanation of a mystery, put forward as the best
which can be offered, until something more shall be
known about the matter. Some theories are in time
found to be the true explanation, but a great many
more have to be thrown aside. No theory should
ever be spoken of as if it were a TRUTH, until it is
plainly proved to be such, with no possibility of mis-
So with regard to the earth's inside and what it is
made of, we cannot get beyond theories. But when
we speak of the earth's crust, the real domain of geo-
logy, there is not the same sort of difficulty, since
here we can see; and feel, and examine for ourselves.
8 Wkat tke Earth's Crust is Made of.
The materials of which the crust is made are many
and various, yet, generally speaking, they may all be
classed under one simple word, and that word is-
It must be understood that, when we talk of rock in
this geological sense, we do not only mean hard and
solid stone, as in common conversation. Rock may be
changed by heat into a liquid or 'molten state, as ice
is changed by heat to water. Liquid rock may be
changed by yet greater heat to vapour, as water is
changed to steam, only we have in a common way no
such heat at command as would be needed to effect
this. Rock may be hard or soft. Roek may be chalky,
clayey, or sandy. Rock may be so close-grained that
strong force is needed to break it; or it may be so
porous-so full of tiny holes-that water will drain
through it; or it may be crushed and crumbled into
loose grains, among which you can pass your fingers.
The cliffs above our beaches are rock; the sand
upon our seashore is rock; the clay used in brick-
making is rock; the limestone of the quarry is rock;
the marble of which our mantel-pieces are made is
rock. The soft sandstone of South Devon, and the
hard granite of the north of Scotland, are alike rock.
The pebbles in the road are rock; the very mould in
our gardens is largely composed of crumbled rock.
What the Eartk's Crust is Made of. 9
So the word in its geological sense is a word of wide
Now the business of the geologist is to read the
history of the past in these rocks of which the earth's
crust is made. This may seem a singular thing to
do, and I can assure you it is not an easy task.
For, to begin with, the history itself is written in a
strange language, a language which man is only just
beginning to spell out and understand. And this is
only half the difficulty with which we have to
If a large and learned book were put before you,
and you were set to read it through, you would, per-
haps, have no insurmountable difficulty, with patience
and perseverance, in mastering its meaning.
But how if the book were first chopped up into
pieces, if part of it were flung away out of reach, if
part of it were crushed into a pulp, if the numbering
of the pages were in many places lost, if the whole
were mixed up in confusion, and if then you were
desired to sort, and arrange, and study the volume ?
Picture to yourself what sort of a task this would
be, and you will have some idea of the labours of the
'The waters wear the stones.'-JoB xiv. 19.
ROCKS may be divided into several kinds or classes.
For the present moment it will be enough to consider
the two grand divisions-STRATIFIED ROCKS and
Unstratified rocks are those which were once, at a
time more or less distant, in a melted state from
intense heat, and which have since cooled into a half
crystallized state; much the same as water, when
growing colder, cools and crystallizes into ice. Strictly
speaking, ice is rock, just as much as granite and
sandstone are rock. Water itself is of the nature of
rock, only as we commonly know it in the liquid state
we do not commonly call it so.
'Crystallization' means those particular forms or
Water-Built Rocks. 11
shapes in which the particles of a liquid arrange
themselves, as that liquid hardens into a solid-in
other words, as it freezes. Granite, iron, marble, are
frozen substances, just as truly as ice is a frozen
substance; for with greater heat they would all become
liquid like water. When a liquid freezes, there are
always crystals formed, though these are not always
visible without the help of a microscope. Also the
crystals are of different shapes with different sub-
If you examine the surface of a puddle or pond,
when a thin covering of ice is beginning to form, you
will be able to see plainly the delicate sharp needle-
like forms of the ice crystals. Break a piece of ice,
and you will find that it will not easily break just in
any way that you may choose, but will only split
along the lines of these needle-like crystals. This
particular mode of splitting in a crystallized rock is
called the cleavage of that rock.
Crystallization may take place either slowly or
quickly, and either in the open air or far below
ground. The lava from a volcano is an example of
rock which has crystallized in the open air; and
granite is an example of rock which has crystallized
underground beneath great-pressure.
Stratified rocks, on the contrary, which make up a
very large part of the earth's crust,' are not crystal-
lized. Instead of having cooled from a liquid into a
solid state, they have been slowly built up, bit by bit
and grain upon grain, into their present form, through
long ages of the world's history. The materials of
which they are made were probably once, long long
ago, the crumblings from granite and other crystallized
rocks, but they show now no signs of crystallization.
They are called 'stratified' because they are in
themselves made up of distinct layers, and also
because they lie thus one upon another in layers, or
strata, just as the leaves of a book lie, or as the bricks
of a house are placed.
Throughout the greater part of Europe, of Asia, of
Africa, of North and South America, of Australia,
these rocks are to be found, stretching over hun-
dreds of miles together, north, south, east, and west,
extending up to the tops of some of the earth's
highest mountains, reaching down deep into the earth's
crust. In many parts, if you could dig straight down-
wards through the earth for thousands of feet, you
would come to layer after layer of these stratified
rocks, one kind below another, some layers thick,
some layers thin, here a stratum of gravel, there a
stratum of sandstone, here a stratum of coal, there a
stratum of clay.
SBut how, when, where, did the building up of all
these rock-layers take place?
People are rather apt to think of land and water on
the earth as if they were fixed in one changeless form,
-as if every continent and every island were of exactly
the same shape and size now that it always has been
and always will be.
Yet nothing can be further from the truth. The
earth-crust is a scene of perpetual change, of perpetual
struggle, of perpetual building up, of perpetual wear-
The work may go on slowly, but it does go on.
The sea is always fighting against the land, beating
down her cliffs, eating into her shores, swallowing bit
by bit of solid earth; and rain and frost and inland
streams are always busily at work, helping the ocean
in her work of destruction. Year by year and century
by century it continues. Not a country in the world
which is bordered by the open sea has precisely the
same coast-line that it had one hundred years ago;
not a land in the world but parts each century with
masses of its material, washed piecemeal away into the
Is this hard to believe? Look at the crumbling
cliffs around old England s shores. See the effect
14 Water-Built Rocks.
upon, the beach of one night's fierce storm.. Mark
the pathway on the cliff, how it, seems to; have crept
so near the edge that here and there it is scarcely safe
to tread ; and. very soon, as. we: know, it ,will, become
impassable. Just. from a mere.accident, of. course,-
the breaking away of some of the earth, loosened..by
rain-and frost and wind. .But this is.an accident which
happens daily in hundreds of places around, our
Leaving the ocean,.look nov at this river in?.our
neighbourhood,, and see the slight muddiness, which
seems to colour its waters. What from? Only a
little earth and sand carried.off from the banks as it
flowed-very unimportant and small in quantity;
doubtless, just at this moment and just at this spot.
But what of that little going on week after week, and
century after century, throughout the whole course of
the river; ay, and throughout the whole course of
every river and rivulet in our whole country and in
every other country. A vast amount of material must
every year be thus torn from the land and given to
the ocean. For the land's loss here is the ocean's gain.
And, strange to say, we shall find that this same
ocean, so busily engaged with the help of its tributary
rivers in pulling down land, is no less busily engaged
with their help in building it up.
Water-Built Rocks: 15
You have sometimes seen directions upon a phial of
medicine to 'shake' before taking the dose. When
you have so shaken the bottle the clear liquid grows
thick ; and if you let it stand for a while the thickness
goes off, and a fine grain-like or dust-like substance
settles down at the bottom-the settlement or sedi-
ment of the medicine. The finer this sediment, the
slower it is in settling. If you were to keep the liquid
in gentle motion, the fine sediment would not settle
down at the bottom. With coarser and heavier
grains the motion would have to be quicker to keep
them supported in the water.
Now it is just the same thing with our rivers and
streams. Running water can support and carry along
sand and earth, which in still water would quickly
sink to the bottom; and the more rapid the move-
ment of the water, the greater is the weight it is able
This is plainly to be seen in the case of a mountain
torrent. As it foams fiercely through its rocky bed
it bears along, not only mud and sand and gravel,
but stones and even small rocks, grinding the latter
roughly together till they are gradually worn away,
first to rounded pebbles, then to sand, and finally to
mud. The material thus swept away by a stream,
ground fine, and carried out tosea-part beiig dropped
S6 Water-Built Rocks.
by the way on the river-bed-is called detritus, which
simply means worn-out material.
The tremendous carrying-power of a mountain
torrent can scarcely be realized by those who have
not observed it for themselves. I have seen a little
mountain-stream swell in the course of a heavy
thunderstorm to such a torrent, brown and turbid with
earth torn from the mountain-side, and sweeping
resistlessly along in its career a shower of stones and
rock-fragments. That which happens thus occasionally
with many streams is more or less the work all the
year round of many more.
As the torrent grows less rapid, lower down in its
course, it ceases to carry rocks and stones, though the
grinding and wearing away of stones upon the rocky
bed continues, and coarse gravel is borne still'upon its
waters. Presently the widening stream, flowing yet
more calmly, drops upon its bed all such coarser
gravel as is not worn away to fine earth, but still
bears on the lighter grains of sand. Next the slacken-
ing speed makes even the sand too heavy a weight,
and that in turn falls to line the river-bed, while the
now broad and placid stream carries only the finer
particles of mud suspended in its waters. Soon it
reaches the ocean, and the flow being there checked
by the incoming ocean-tide, even the mud can no
Water-Built Rocks. .
longer be held up, and it also sinks slowly in the
shallows near the shore, forming sometimes broad
mud-banks dangerous to the mariner.
This is the case only with smaller rivers. Where
the stream is stronger, the mud-banks are often
formed much farther out at sea; and more often
still the river-detritus is carried away and shed over
the ocean-bed, beyond reach of our ken. The power-
ful rush of water in earth's greater streams bears
enormous masses of sand and mud each year far out
into the ocean, there dropping quietly the gravel,
sand, and earth, layer upon layer at the bottom of the
sea. Thus pulling down and building up go on ever
side by side; and while land is the theatre often-
times of decay and loss, ocean is the theatre often-
times of renewal and gain.
Did you notice the word Sediment used a few pages
back about the settlement at the bottom of a medicine-
There is a second name given to the Strati-
fied Rocks, of which the earth's crust is so largely
made up. They are called also SEDIMENTARY
The reason is simply this. -The Stratified Rocks of
the present day were once upon a time made up out of
18 Water-Built Rocks.
the sediment stolen first from land and then allowed
;o settle down on the sea-bottom.
Long, long ago the rivers, the streams, the ocean,
were at work, as they are now, carrying away rock
and gravel, sand and earth. Then, as now, all this
material, borne upon the rivers, washed to and fro by
the ocean, settled down at the mouths of rivers or at
the bottom of the sea, into a sediment, one layer form-
ing over another, gradually built up through long
ages. At first it was only a soft loose sandy or
muddy sediment, such as you may see on the sea-
shore, or in a mud-bank. But as the thickness of the
sediment increased, the weight of the layers above
gradually pressed the lower layers into firm hard
rocks; and still, as the work of building went on,
these layers were, in their turn, made solid by the
increasing weight over them. Certain chemical
changes had also a share in the transformation from
soft mud to hard rock, which need not be here con-
All this has through thousands of years been going
on. The land is perpetually crumbling away; and
fresh land under the sea is being perpetually built up,
from the very same materials which the sea and the
rivers have so mercilessly stolen from continents and
islands. This is the way, if geologists rightly judge,
Water-Built Rocks. 19
in which a very large part of the enormous forma-
tions of Stratified or Sedimentary Rocks have been
So far is clear. But now we come to a difficulty.
FGSSILS IN THE ROCKS.
*Dead things are formed from under the waters with the in-
habitants thereof.'-Job xxvi. 5 (marg.).
THE Stratified Rocks, of which a very large part of the
continents is made, appear to have been built up
slowly, layer upon layer, out of the gravel, sand, and
mud, washeJ away from the land and dropped on the
floor of the ocean.
You may see these layers for yourself as you walk
out into the country. Look at the first piece of bluff
rock you come near, and observe the clear pencil-like
markings of layer above layer-not often indeed lying
flat, one over another, and this must be explained
later, but however irregularly slanting, still plainly
visible. You can examine these lines of stratifica-
tion on the nearest cliff, the nearest quarry, the nearest
bare headland, in your neighbourhood.
Fossils in the Rocks. 21
But how can this be ? If all these stratified rocks
are built on the floor of the ocean out of material
taken from the land, how can we by any possibility
find such rocks upon the land ? In the beds of rivers
we might indeed expect to see them, but surely no-
where else save under ocean waters.
Yet find them we do. Through England, through
the two great world-continents, they abound on every
side. Thousands of miles in unbroken succession are
composed of such rocks.
Stand with me near the sea-shore, and let us look
around. Those white chalk cliffs-they, at least, are
not formed of sand or earth. True, and the lines of
stratification are in them very indistinct, if seen at
all; yet they too are built up of sediment of a
different kind, dropping upon ocean's floor. More of
this later. See, however, in the rough sides of yonder
bluff the markings spoken of, fine lines running along-
side of one another, sometimes flat, sometimes bent
or slanting, but always giving the impression of layer
piled upon layer. Yet how can one for a moment
suppose that the ocean-waters ever rose so high ?
Stay a moment. Look again at yonder white
chalk cliff, and observe a little way below the top a
singular band of shingles, squeezed into the cliff, as it
were, with chalk below and earth above.
Fossils in the Rocks..
That is believed to be an old sea-beach. Once
upon a time the waters of the sea are supposed to
have washed those shingles, as now they wash the
shore near which we stand, and all the white cliff
must have lain then beneath the ocean.
Geologists were for a long while sorely puzzled to
account for these old sea-beaches, found high up in
the cliffs around our land in many different places.
They had at first a theory that the sea must once,
in far-back ages, have been a great deal higher than
it is now. But this explanation only brought about
fresh difficulties. It is quite impossible that the level
of the sea should be higher in one part of the world'
than in another. If the sea around England were
then one or two hundred feet higher than it is now,
it must have been one or two hundred feet higher in
every part of the world where the ocean-waters have
free flow. One is rather puzzled to know where all
the water could have come from, for such a tremendous
additional amount. Besides, in some places remains
of sea-animals are found in mountain heights, as much
as two or three thousand feet above the sea-level-as,
for instance, in Corsica. This very much increases
the difficulty of the above explanation.
:So another theory was started instead, and this is:
now generally supposed to be the true one. What if,
Fossils in the Rocks. 23
instead of the whole ocean having been higher, parts
of the land were lower? England at one time, parts
of Europe at another time, parts of Asia and America
at other times, may have slowly sunk beneath the
ocean, and after long remaining there have slowly
This is by no means so wild a supposition as it may
seem when first heard, and as it doubtless did seem
when first proposed. For even in the present day
these movements of the solid crust of our earth are
going on. The coasts of Sweden and Finland have
long been slowly and steadily rising out of the sea,
so that the waves can no longer reach so high upon
those shores as in years gone by they used to reach.
In Greenland, on the contrary, land has long been
slowly and steadily sinking, so that what used to be
the shore now lies under the sea. Other such risings
and sinkings might be mentioned, as also many more
in connection with volcanoes and earthquakes, which
are neither slow nor steady, but sudden and violent;
So it becomes no impossible matter to believe that,
in the course of ages past, all those wide reaches of
our continents and islands, where sedimentary rocks
are to be found, were each in turn, at one time or
another, during long periods, beneath the rolling waters
of the ocean.
24 Fossils in the Rocks.
It should be clearly understood that, in speaking
of those probable long-past ages of slow prepara-
tion, about which the rocks seem to tell us, I am not
in anywise touching upon the question of the flood
upon the.earth in the time of Noah. That was com-
paratively a recent event. Whether it was entirely
miraculous, or whether it was in part caused by some
great and rapid sinking of the land, is an interesting
consideration, with which, however, we are at this
moment not concerned. The slow building up of
the continents under the ocean could have taken
place in no such brief space of time as the few months
of the deluge in Noah's days, but must have occupied
very long periods.
These built-up rocks are not only called 'Strati-
fled,' and 'Sedimentary.' They have also the name
of 'AQUEOUS ROCKS,' from the Latin word aqua,
water; because they are believed to have been
formed by the action of water.
They have yet another and fourth title, which is,
Fossils are the hardened remains of animals and
vegetables found in rocks. They are rarely, if ever,
seen in unstratified rocks; but many layers of stratified
rocks abound in these remains. Whole skeletons as
Fossils in the Rocks. 25
well as single bones, whole tree-trunks as well as
single leaves, are found thus embedded in rock-layers,
where in ages past the animal or plant died and
found a grave. They exist by thousands in many
parts of the world, varying in size from the huge
skeleton of the elephant to the tiny shell of the
Fossils differ greatly in kind. Sometimes the
entire shell or bone is changed into stone, losing all
its animal substance, but retaining its old outline and
its natural markings. Sometimes the fossil is merely
the hardened impress of the outside of a shell or leaf,
which has dented its picture on soft clay, and has
itself disappeared, while the soft clay has become
*rock, and the indented picture remains fixed through
after-centuries. Sometimes the fossil is the cast of
the inside of a shell; the said shell having been filled
with soft mud, which has taken its exact shape and
hardened, while the shell itself has vanished. The
most complete description of fossil is the first of these
three kinds. It is wonderfully shown sometimes
in fossil wood, where all the tiny cells and delicate
fibres remain distinctly marked as of old, only the
whole woody substance has changed into .hard
But although the fossil remains of quadrupeds
26 Fossils in the Rocks.
and other land-animals are found in large quan-
tities, still their number is small compared with
the enormous amount of fossil sea-shells and sea-
Land-animals can, as a rule, have been so preserved,
only when they have been drowned in ponds or rivers,
or mired in bogs and swamps, or overtaken by frost,
or swept out to sea.
Sea-animals, on the contrary, have been so pre-
served on land whenever that land has been under
the sea; and this appears to have been the case, at
one or another past age, with the greater part of our
present continents. These fossil remains of sea-
animals are discovered in all quarters of the world,
not only on the sea-shore but also far inland, not
only deep down underground but also high up on the
tops of lofty mountains-a plain proof that over
the summits of those mountains the ocean must once
have rolled, and this not for a brief space only, but
through long periods of time. And not on the
mountain-summit only are these fossils known to
abound, but sometimes in layer below layer of the
mountain, from top to bottom, through thousands of
feet of rock.
This may well seem puzzling at first sight. Fossils
of sea-creatures on a mountain-top are startling
Fossils in the Rocks. 27
enough; yet hardly so startling as the thought of
fossils inside that mountain. How could they have
found their way thither?
The difficulty soon vanishes, if once we clearly
understand that all these thousands of feet of rock
were built up slowly, layer after layer, when that por-
tion of the land lay deep under the sea. Thus each
separate layer of mud or sand or other material became
in its turn the top layer, and was for the time the
floor of the ocean, until further droppings of material
out of the waters made a fresh layer, covering up the
While each layer was thus in succession the top
layer of the building, and at the same time the floor
of the ocean, animals lived and died in the ocean, and
their remains sank to the bottom, resting upon the
sediment floor. Thousands of such dead remains
disappeared, crumbling into fine dust and mingling
with the waters, but here and there one was caught
captive by the half-liquid mud, and was quickly covered
and preserved from decay. And still the building
went on, and still layer after layer was placed, till
many fossils lay deep down beneath the later-formed
layers; and when at length, by slow or quick upheaval
of the ground, this sea-bottom became a mountain, the
little fossils were buried within the body of that
Fossils in the Rocks.
mountain. So wondrously the matter appears to
have come about.
Another difficulty with respect to the stratified
rocks has to be thought of. All these layers or de-
posits of gravel, sand, or earth, on the floor of the
ocean, would naturally be horizontal-that is, would
lie flat, one upon another. In places the ocean-floor
might slant, or a crevice or valley or ridge mih'-
break the smoothness of the deposit. But though the
layers might partake of the slant, though the valley
might have to be filled, though the ridge might have to
be surmounted, still the general tendency of the waves
would be to level the dropping deposits into flat layers.
Then how is it that when we examine the strata of
rocks in our neighbourhood, wherever that neighbour-
hood may be, we do not find them so arranged?
Here, it is true, the lines for a space are nearly
horizontal, but there, a little way farther on, they are
perpendicular; here they are bent, and there curved ;
here they are slanting, and there crushed and broken.
This only bears out what has been already said
about the Book of Geology. It has been bent and
disturbed, crushed and broken.
Great powers have been at work in this crust of
our earth. Continents have been raised, mountains
Fossils in the Rocks. 29
have been upheaved, vast masses of rock have been
scattered into fragments. Here or there we may find
the layers arranged as they were first laid down; but
far more often we discover signs of later disturbance,
either slow or sudden, varying from a mere quiet
tilting to a violent overturn.
So the Book of Geology is a torn and disorganized
volume, not easy to read.
Yet, on the other hand, these very changes which
have taken place are a help to the geologist.
It may seem at first sight as if he would have an
easier task, if the strata were all left lying just as they
were first formed, in smooth level layers, one above
another. But if it were so, we could know very little
about the lower layers.
We might indeed feel sure, as we do now, that the
lowest layers were the oldest and the top layers the
newest, and that any fossils found in the lower layers
must belong to an age farther back than any fossils
found in the upper layers.
So much would be clear. And we might dig also
and burrow a little way down, through a few different
kinds of rock, where they were not too thick. But that
would be all. There our powers would cease.
Now how different. Through the hearings and
tilting of the earth's crust, the lower layers are often
30 Fossils in the Rocks.
pushed quite up to the surface, so that we are able to
examine them and their fossils without the least
difficulty, and very often without digging under-
ground at all.
You must not suppose that the real order of the rocks
is changed by these movements, for generally speaking
it is not. The lower kinds are rarely if ever found
placed over the upper kinds; only the ends of them
are seen peeping out above ground.
It is as if you had a pile of copy-books lying flat
one upon another, and were to put your finger under
the lowest and push it up. All those above would be
pushed up also, and perhaps they would slip a little way
down, so that you would have a row of edges showing
side byside, atverymuch the same height. Thearrange-
ment of the copy-books would not be changed, for the
lowest would still be the lowest in actual position ; but
a general tilting or upheaval would have taken place.
Just such a tilting or upheaval has taken place
again and again with the rocks forming our earth-
crust. The edges of the lower ones often show side
by side with those of higher layers.
But geologists know them apart. They are able to
tell confidently whether such and such a rock, peeping
out at the earth's surface, belongs really to a lower or
a higher kind. For there is a certain sort of order
Fossils in the Rocks.
followed in the arrangement of the layers all over
the earth, and it is well known that some rocks
are never found below some other rocks, that cer-
tain particular kinds are never placed above certain
other kinds. Thus it follows that the fossils found in
one description of rock, must be the fossils of animals
which lived and died before the animals whose fossil
remains are found in another neighboring rock, just
because this last layer was built upon the ocean-floor
above and therefore later than the other.
All this is part of the foreign language of geology-
part of the piecing and arranging of the torn volume.
Many mistakes are made; many blunders are possible:
but the mistakes and blunders are being gradually
corrected, and certain rules by which to read and
understand are becoming more and more clear.
'For all those things hath Mine Hand made, and all thost
things have been, saith the Lord.'-ISA. Ixvi. 2.
IT has been already said that Unstratified Rocks are
those which have been at some period, whether lately
or very long ago, in a liquid state from intense heat,
and which have since cooled, either quickly or slowly,
crystallizing as they cooled.
Unstratified Rocks may be divided into two distinct
First-Volcanic Rocks, such as lava. These have
been cooled at the surface of the earth, or not far
Secondly-Plutonic Rocks, such as granite. These
have been cooled deep down in the earth, under
There is also a class of rocks, called Metamorphic
Rocks, including some kinds of marble. These
are, strictly speaking, crystalline rocks, and yet
they are arranged in something like layers. The
word 'metamorphic' simply means 'transformed.'
They are believed to have been once stratified rocks,
perhaps containing often the remains of animals ; but
intense heat has later transformed them into crystal-
'line rocks, and the animal remains have almost or
Just as the different kinds of Stratified Rocks are
often called Aqueous Rocks, or rocks formed by the
action of water-so these different kinds of Unstrati-
fied Rocks are often called Igneous Rocks, or rocks
formed by the action of fire-the name being taken
from the Latin word ignis, fire. The Metamorphic
Rocks are sometimes described as 'Aqueo-igneous,'
since both water and fire helped in the forming of them.
It was at one time believed, as a matter of cer-
tainty, that granite and such rocks belonged to a
period much farther back than the periods of the
stratified rocks. That is to say, it was supposed that
fire-action had come first and water-action second;
that the fire-made rocks were all formed in very early
ages, and that only water-made rocks still continued
to be formed. So the name of Primary or First Rocks
S34 Fire-Built Rocks.
was given to the granites and other such kinds,
and the name of Secondary to all water-built kinds;
while those of the third class were called Transition
Rocks, because they seemed to be a kind of link
or stepping-stone in the change from the First to the
The chief reason for the general belief that fire-
built rocks were older than water-built ones was,
that the former are as a rule found to lie lower than
the latter. They form, as it were, the basement of
the building, while the top-stories are made of water-
Many still believe that there is much truth in the
thought. It is most probable, so far as we are able
to judge, that the first-formed crust all over the
earth was of cooled and crystallized material. As
these rocks were crumbled and wasted by the ocean,
materials would have been supplied for the building-
up of layer upon layer.
But this is conjecture. We cannot know with
any certainty the course of events so far back in the
past. And geologists are now able to state with
tolerable confidence that, however old many of the
granites may be, yet a large amount of the fire-built
rocks are no older than the water-built ones which lie
Fire-Built Rocks. 35
So by many geologists the names of Primary, Trarin
sition, and Secondary Formations are pretty well
given up. It has been proposed to give instead'td
all the. crystallized kinds the name of Underlying
But .if they really do lie under, how can .theynpos'
sibly be of the same age ? One would scarcely venture,
to suppose, in looking at a building, that the cellars
had not been finished before the upper floors.
True. In the first instance doubtless the cellars
were first made, then the ground-floor, then the upper
When, however, the house was so built, alterations:
and improvements might be very widely carried on;
above and below. While one set of workmen were
engaged in remodelling the roof, another set of work-
men might be engaged in remodelling the kitchens
and first floor, pulling down, propping up, and actu-;
ally rebuilding parts of the lower, walls.
This is precisely what the .two, great fellow-work*4
men, Fire and Water, are ever doing in the crust .oft
our earth. And if it be objected that such. alterations,.
too widely undertaken, might result in slips, cracks,
and sliding, of ceilings and walls in.the upper stories;i
36 Fire-Built Rocks.
I can only say that such catastrophes have been the
result of underground alterations in that great build-
ing, the earth's crust.
For these two leading powers of Nature have been,
since the earliest ages of the world's history, perpetu-
ally at work, modelling and remodelling, pulling down
and building up, each to some extent hindering and
yet to some extent helping the other.
By 'powers of Nature' I mean simply powers used
by God in nature. For this Nature,' of which we
hear so much, is but the handiwork of God, the
Divine Architect. The powers seen in nature, Fire
and'Water, Heat and Frost, Gravitation and Elec-
tricity, these and a hundred others are His servants,
ordained from earliest ages to carry out His will.
We see therefore clearly that, although the first
fire-made rocks may very likely date farther back
than the first water-made rocks,' yet the making of
the two kinds has gone on side by side, one below
and the other above ground, through all ages up to
the present moment. ...... .
SAnd just as in the present day water continues its
busy work above ground of pulling down and building
ap, so also fire continues its busy work underground of
melting rocks which afterwards cool into new forms,
Fire-Built Rocks. 37
and also of shattering and upheaving parts of the
For there can be no doubt that fiery heat does exist
as a mighty power within our earth, though to what
extent we are not able to say.
These two fellow-workers in nature have different
modes of working. One we can see on all sides, quietly
progressing, demolishing land patiently bit by bit,
building up land steadily grain by grain. The other,
though more commonly hidden from sight, is fierce
and tumultuous in character, and shows his power in
occasional terrific outbursts.
We in our placid island-home can scarcely realize
what the power is of the imprisoned fiery forces under-
ground, though even we are not without some witness
of their existence. From time to time even our
firm land has been felt to tremble with a thrill from
some far-off shock ; and even in our country is seen the
marvel of scalding water pouring unceasingly from
deep underground. Where is the furnace that heats
the boiler whence flow those steaming waters in the
pleasant town of Bath? What also of the wide
hollow, probably an ancient extinct crater, in which the
town is built ? There have surely been past workings of
underground furnace-heat in that neighbourhood, not
entirely at an end even now.
t Fire-Buil 'Rocks.
'w-But it is when wer.ead about other countries that
we better realize the existence of this power.
.Think of the. tremendous eruptions of Vesuvius, of
.Etna,'of HIecla, of Mauna Loa.- Think bfiwhole towns
crushed and buried, with theirthousands of living in-
habitants. Thihk of rivers of glowing lava streaming
up from:.regions.below ground, and pouring along the
sttrface for a. distance of forty, fifty,i and;,even- sixty
miles, as in Icelanda-and :Hawaii. Think.of;red-hot
cinders flung from'a volcano-craterto-a.height-of: ten
thousand feet. Think of lakes of liquid, firein other
craters, five hundred to a thousand feet across, huge
:cauldrons of boiling rock.': Think of showers of ashes
from the furnace below of yet another, borne-so high
aloft as to be carried seven hundred miles before they
sank, to. earth again. Think of millions of -red-hot
stones flung out.ino6ne eruption of Vesuvius. -Think
of.av :mass of rock., one hundred, cubic. yards, in size,
hurled to a distance of eight miles or more out of the
crater of Cotopaxi.
.Think also of earthquake-shocks felt through
twelve hundred miles of country. Think of fierce
tremblings and hearings lasting in constant succession
through days and weeks of terror. Think of hundreds
of miles of land raised several feet in one great, up-
heavaL Think of the earth opening in scores of wide-
Fire-Built Rocks. 39
lipped cracks, to swallow men and beasts. Think of
Shot mud, boiling water, scalding steam, liquid rock,
Bursting from such cracks, or pouring from rents in a
Truly these are signs of a state of things in or
-below the solid crust on which we live, that may make
us doubt the absolute security of Mother Earth.'
Different explanations have been put forward to
explain this seemingly fiery state of things under-
Until lately the belief was widely held that our
earth was one huge globe of liquid fire, with only
a slender cooled crust covering her, a few miles in
:This view was supported by the fact that heat is
found to increase as men descend into the earth.
Measurements of such heat-increase have been taken,
both in mines and in borings for wells. The usual
rate is about one degree more of heat, of our common
Thermometer, for every fifty or sixty feet of descent.
If this were steadily continued, water would boil at
a depth of eight thousand feet below the surface; iron
would melt at a depth of twenty-eight miles; while
*at a depth of forty or fifty miles no known substance
*Iupon earth could remain solid.
The force of this proof is, however, weakened by
the fact that the rate at which the heat increases
differs very much in different places. Also it is now
generally supposed that such a tremendous furnace of
heat-a furnace nearly eight thousand miles in
diameter-could not fail to break up and melt so slight
a covering shell.
Many believe, therefore, not that the whole interior
of the earth is liquid with heat, but that enormous
fire-seas or lakes of melted rock exist here and there,
under or in the earth-crust. From these lakes the
volcanoes would be fed, and they would be the cause
of earthquakes and land-upheavals or land-sinkings.
There are strong reasons for supposing that the earth
was once a fiery liquid body, and that she has slowly
cooled through long ages. Some hold that her centre
probably grew solid first from tremendous pressure;
that her crust afterwards became gradually cold ; and
that between the solid crust and the solid inside or
'nucleus,' a sea of melted rock long existed, the
remains of which are still to be found in these tre-
mendous fiery reservoirs.
This idea accords well with the fact that large
numbers of extinct or dead volcanoes are scattered
through many parts of the earth. If the above ex-
planation be the right one, doubtless the fire-seas in
the crust extended once upon a time beneath such
volcanoes, but have since died out or smouldered low
in those parts.
A somewhat curious calculation has been made, to
illustrate the different modes of working of these
two mighty powers-Fire and Water.
The amount of land swept away each year in mud,
and borne to the ocean by the River Ganges, was
roughly reckoned, and also the amount of land
believed to have been upheaved several feet in the
great Chilian earthquake.
It was found that the river, steadily working month
by month, would require some four hundred years to
carry to the sea the same weight of material, which in
one tremendous effort was upheaved by the fiery
Yet we must not carry this distinction too far.
Fire does not always work suddenly, or water slowly;
witness the slow rising and sinking of land in parts of
the earth, continuing through centuries; and witness
also the effects of great floods and storms.
WHAT ROCKS ARE MADE OF.
"God ... which doeth great things and unsearchable;
marvellous things without number."-JoB v. 8, 9.
THE crust of the earth is made of rock. But what is
rock made of?
Certain leading divisions of rocks have, been already
The Water-made Rocks;
The Fire-made Rocks, both Plutonic and Vnlcanic;
The Water-and-Fire-made Rocks.
The first of these-Water-made Rocks-may be
subdivided into three classes. These are,-
I. FLINT ROCKS;
II. CLAY ROCKS;
III. LIME ROCKS.
This is not a book in which it would be wise to go
WJVhadtRocks are -Made of. 43
closely into. the mineral nature of rocks. Two or
'three leading thoughts may, however, be given.
Does it not seem strange that the hard and solid
,rocks should be ingreat measure formed of the same
:substances which form the thin invisible air floating
, 'Yet so it is. There is a certain gas called Oxygen
,Gas. Without that gas you could not live many
,minutes. Banish it from the room in which you are
sitting, and in a few minutes you will die.
This gas makes up nearly one quarter byweight
of the atmosphere round the whole earth.
The same gas plays an important part in the
,oceans; for more than three-quarters of water is
It plays also:-an important part in rocks; for about
.half the material of the entire earth's crust is
S-.Another chief material in rocks is SILICON. This
:makes up one more quarter of the crust, leaving only
one quarter to be accounted for. Silicon mixed with
oxygen makes silica or quartz. There are few rocks
which have not a large amount of quartz in them.
Common flint, sandstones, and the sand of our shores,
are made of quartz, and therefore belong to the first
'class of Silicious or Flint Rocks. Granites and lavas
44 What Rocks are Made of
are about one-half quartz. The beautiful stones, ame-
thyst, agate, chalcedony, and jasper, are all different
kinds of quartz.
Another chief material in rocks is a white metal
called ALUMINIUM. United to oxygen it becomes
alumina, the chief substance in clay. Rocks of this
kind-such as clays, and also the gems, sapphire,
ruby, oriental topaz, oriental emerald, and oriental
amethyst, all differing only in colour,-are called
Argillaceous Rocks, from the Latin word for clay,
and belong to the second class. Such rocks keep
Another is CALCIUM. United to oxygen and
carbonic acid, it makes carbonate of lime, or pure
limestone; therefore all limestones belong to the
third class of Calcareous or Lime Rocks.
Other important materials might be mentioned,
such as MAGNESIUM, POTASSIUM, SODIUM, IRON,
CARBON, SULPHUR, HYDROGEN, CHLORINE, and
NITROGEN. These, with many more, not so common,
make up the remaining quarter of the earth-crust.
Carbon plays as important a part in animal and
vegetable life as silicon in rocks. Carbon is most
commonly seen in three distinct forms--as charcoal,
as black-lead, and as the pure brilliant diamond,
Carbon united in a particular proportion to oxygen
What Rocks are Made of. 45
forms carbonic acid, and carbonic acid united in a
particular proportion to lime forms limestone.
HYDROGEN united to oxygen forms water. Each
of these two gases is invisible alone, but together
they combine to form a liquid.
NITROGEN mingled with oxygen and a small
quantity of carbonic acid gas forms our atmos-
In the fire-built rocks no remains of animals
are found, though in water-built rocks they abound.
Water-built rocks are sometimes divided into two
classes-those which only contain occasional animal
remains, and those which are more or less built up of
the skeletons of animals.
There are some exceedingly tiny creatures in-
habiting the ocean, called Rhizopods. They live in
minute shells, the largest of which may be almost
the size of a grain of wheat, but by far the greater
number are invisible as shells without a microscope,
and merely show as fine dust. The Rhizopods are of
different shapes, sometimes round, sometimes spiral,
sometimes having only one cell, sometimes having
several cells. In the latter case a separate animal
lives in each cell. The animal is of the very simplest
as well as the smallest kind. It has not even a
46. What Rocks areMade of.'
mouth or a stomach, but can take in food at any part"
of its body.
These. rhizopods live in the oceans in enormous
numbers. :Tens of millions are ever coming into,
existence, living out their tiny lives, 'dying,: and-sink -.
ing 'to the bottom.
There upon the ocean-floor gather their-s remains;
a heaped-up multitude of minute skeletons or shells,
layer forming over layer.
It was long suspected that the white chalk cliffs of
England were built up in some such manner as this:
through past ages. And now at length proof has
been found, in the shape of mud dredged up from the,
ocean-bottom-mud entirely composed of countless
multitudes of these little shells, called Foraminifers;
dropping there by myriads, and becoming slowly
joined together in one mass.
Just so, it is believed, were the white chalk cliffs
built -gradually prepared on the ocean-floor, and'
then slowly or suddenly upheaved, so as to become
a part of the dry land.
Think what the enormous numbers must have been'
of tiny living creatures, out of whose shells 'the wide'
reaches of white chalk have been made. Chalk cliffs
and chalk layers extend from Ireland, through Efig-
land and France, as far as to the Crimea. In the
What Rocks are Made- of 47
south of Russia they are said to be six hundred feet
thick. Yet one cubic inch of chalk is calculated to.
hold the remains of more than one million rhizopods.
How many countless millions upon millions must
have gone to the whole structure How long must
the work of building up have lasted !
These little shells do not always drop softly and;
evenly to the ocean-floor, to become quietly part of,
a mass of shells. Sometimes, where the ocean is'
shallow enough for the waves to have power below,
or where land currents can reach, they are washed:
about, and thrown one against another, and ground:
into fine powder; and the fine powder becomes in
time, through different causes, solid rock.
Limestone is made in another way also. In the
warm waters of the South Pacific Ocean there are
many islands, large and small, which have been formed
in a wonderful manner by tiny living workers. The
workers are soft jelly-like creatures, called polyps, who
labour together in building up great walls and masses.
They never carry on their work above the surface-
of the water, for in the air they would die. But the
waves break the coral, and heap it up above high-
water mark, till at length a small low-lying islandsis
48, What Rocks are Made of.
The waves not only heap up broken coral, but they
grind the coral into fine powder, and from this powder
limestone rock is made, just as it is from the powdered
shells of rhizopods. The material used by the polyps
inbuilding thecoralis carbonate of lime,which they have
the power of gathering out of the water, and the fine
coral-powder, sinking to the bottom, makes large quan-
tities of hard limestone. Soft chalk is rarely, if ever,
found near the coral islands.
, Limestones are formed in the same manner from
the grinding up of other sea-shells and fossils, various
in kind ; the powder becoming gradually united into
There is yet another way in which limestone is
made, quite different from all these. Sometimes
streams of water have a large quantity of lime in
them; and these as they flow will drop layers of
lime which harden into rock. Or a lime-laden spring,
making its way through the roof of an underground
cavern, will leave all kinds of fantastic arrangements
of limestone wherever its waters can trickle and drip.
Such a cavern is called a 'stalactite cave.'
- So there are different kinds of fossil.rock-making.
There may be rocks made of other materials, with
fossils simply buried in them. There may be rocks
What Rocks are Made of ,49
made entirely of fossils, which have gathered in
masses as they sank to the sea-bottom, and have there
-become simply and lightly joined together. There
may be rocks made of the ground-up powder of
fossils, pressed into a solid substance or united by
Rocks are also often formed of whole fossils, or
stones, or shells, bound into one by some natural soft
cement, which has gathered round them and after-
wards grown hard, like the cement which holds
together the stones in a wall.
The tiny rhizopods,* which have so large a share
in chalk and limestone making, are among the
smallest and simplest known kinds of animal life.
There are also some very minute forms of veget-
able life, which exist in equally vast numbers, called
Diatoms. For a long while they were believed to be
living animals, like the rhizopods. Scientific men
are .now, however, pretty well agreed that they really
are only vegetables or plants.
The diatoms have each one a tiny shell or shield,
not made of lime like the foraminifers, but of flint.
Some think that common flint may be formed of
these tiny shells
SLiteral meaning of word, Rootfogt.
50o W-Jat-Rocks :are _Made of
SAgain, there is a kind of rock called Mountain Meal,
-which is entirely made up of the remains of diatoms.
:Examinedunider the microscope, thousands of minute
flint shields -of various- shapes are seen. This rock,
or earth, is very ab'uridant in many places, and is
sometimes used as a polishing powder. In Bo-
hernia there is a layer of it no less than fourteen
feet thick. Yet so minute are the shells of which
it is composed, that one square inch of rock is said
to contain about four thousand millions of them
Each one of these millions is a separate distinct
One more kind of fossil substance must be touched
upon before the close of this chapter, a kind very
familiar to all of us. from earliest childhood-that
What should we all do without coal? How
necessary it is to comfort, nay, even to life, in cold
countries where an abundance of firewood does not
exist! Yet how many use it, day after day and
year after year, without a thought of the manner in
which it has been provided for them !
Coal comes from underground.- Mines, low-sunk,
and extending far, in some places even beneath the
sea, are made for the purpose of bringing up coal, to
-What Rocks:- are. Made of 51
be used in thousands of homes. But how did it
-first get there ? That is the question.
Coal is a vegetable substance. The wide coal-
fields of Britain and other lands are the fossil remains
of vast forests.
Long ages ago, as it seems, broad and luxuriant
forests flourished over the earth. In many parts
generation after generation of trees lived and died
and decayed, leaving no trace of their existence, be-
yond a little layer of black mould, soon to be carried
away by wind and water. Coal could only be formed
where there were bogs and quagmires.
But in bogs and quagmires, and in shallow lakes of
low-lying lands, there were great gatherings of slowly-
decaying vegetable remains, trees, plants and ferns all
mingling together. Then after a while the low lands
would sink and the ocean pouring in would cover
them with layers of protecting sand or mud; and
sometimes the land would rise again, and fresh forests
would spring into life, only to be in their turn over-
whelmed anew, and covered by fresh sandy or earthy
These buried forests lay through the ages following,
slowly hardening into the black and shining coal, so
useful now to man.
The coal is found thus in thin or thick seams,
What Rocks are Made of
:with other rock-layers between, telling each its history
of centuries long past. In one place no less than
sixteen such beds of coal are found, one below
another, each divided from the next above and the
next underneath by beds of clay or sand or shale.
The forests could not have grown in the sea, and the
earth-layers could not have been formed on land,
therefore many land risings and sinkings must have
taken place. Each bed probably tells the tale of a
succession of forests.
There are in Great Britain about twelve thousand
square miles of coal-fields. In France, in Spain, in
Belgium, though coal-fields do. exist, the amount is
much less. In North America there are about two
hundred and eight thousand square miles of coal-fields.
Baron Richsofen, who has made very extensive ex-
plorations in the Chinese Empire, reports that a large
proportion of that country-a vast area, amounting
to about one million square miles-consists mainly
of coal-deposits. So there is little danger of the
supply running short.
'Before the mountains were brought forth, or ever thou hadst
formed the earth and the world, even from everlasting to ever-
lasting Thou art GOD.'-PSA. xc. 2.
BEFORE going on to a sketch of the early ages of the
Earth's history-ages stretching back long long
before the time of Adam-it is needful to think yet
for a little longer about the manner in which that
history is written, and the way in which it has to be
For the record is one difficult to make out, and its
style of expression is often dark and mysterious.
There is scarcely any other volume in the great Book
of Nature, which the student is so likely to misread as
this one. It is very needful, therefore, to hold the
conclusions of geologists with a light grasp, guarding
each with a perhaps or a may-be." Many an im-'
posing edifice has been built, in geology, upon a
rickety foundation which has speedily given way.
In all ages of the world's history up to the present
day, rock-making has taken place-fire-made rocks
being fashioned underground, and water-made rocks
being fashioned above ground though under water.
Also in all ages different kinds of rocks have been
fashioned side by side-limestone in one part of the
world, sandstone in another, chalk in another, clay in
another, and so on. .There have, it is true, been ages
when one kind seems to have been the chief kind-an
age of limestone, or an age of chalk. But even then
there were doubtless more rock-buildings going on,
though not to so great an extent. On the other hand,
there may have been ages during which no limestone
was made, or no chalk, or no clay. As a general rule,
however, the various sorts of rock-building have pro-
bably gone on together. This was not so well under-
stood by early geologists as it is now.
The difficulty is often great of disentangling the
different strata, and saying which was earlier and
which later formed.
Still, by close and careful study of the rocks which
compose the earth's crust, a certain kind. of order is
found to exist, more or less followed out in all parts
of the world. When each layer was formed in Eng-
land or in- America -the. geologist- cannot: possibly:
say. He can, however, assert, in either place, that'a;
certain mass of rock was formed before a certain-other
mass in that same place,:even though the; two may,
seem to lie side by side ; for he knows- that they-,were:
so placed only by upheaval, and -that once,.:upon:;a:
time the one lay beneath the other.
The geologist can go further; He can often de-
clare that a certain mass of rock in America and a
certain mass of rock in England, quite different in-
kind, were probably built up at about the same time;
How long ago that time. was he would be rash to
attempt to say; but that the two belong to the same
age he has good reason for supposing.
We find rocks piled upon rocks in a certain order,
so that we may generally be pretty confident that the
lower rocks were first made and the. upper rocks the
atest built. Further than this, we find in all the said
ayers of water-built rocks signs of past life.
As already stated, much of this life was ocean-life,
though not all.
Below the sea, as the rock-layers were being formed,
bit by bit, of earth dropping from the ocean to-the
ocean's floor, sea-creatures lived out their lives .and
died by thousands, to sink to that same floor. Mil-
lions passed away, dissolving and, leaving ino- trace
behind; but thousands were preserved-shells often,
Nor was this all. For now and again some part of
the sea-bottom was upheaved, slowly or quickly, till it
became dry land. On this dry land animals lived
again,. and thousands of them, too, died, and their
bones crumbled into dust. But here and there one
was caught in bog or mud, and his remains were pre-
served till, through lapse of ages, they turned to stone.
Yet again that land would sink, and over it fresh
layers were formed by the ocean-waters, with fresh
remains of sea-animals buried in with the layers of
sand or lime; and once more the sea-bottom would
rise, perhaps then to continue as dry land, until the
day when man should discover and handle these
Now note a remarkable fact as to these fossils, scat-
tered far and wide through the layers of stratified rock.
In the uppermost and latest built rocks the animals
found are the same, in great measure, as those which
now exist upon the earth.
Leaving the uppermost rocks, and examining those
which lie a little way below, we find a difference.
Some are still the same, and others, if not quite the
same, are very much like what we have now; but
here and there a creature of a different form appears.
Go deeper still,, and the kinds of animals change
further. Fewer and fewer resemble those which now
range the earth; more and more belong to other
Descend through layer after layer till we come to
rocks built in earliest ages, and not one fossil shall we
find precisely the same as one animal living now.
So not only are the rocks built in successive order,
stratum after stratum belonging to age after age in the
past, but fossil-remains also are found in successive
order, kind after kind belonging to past age after age.
Although in the first instance the succession of
fossils was understood by means of the succession of
rock-layers, yet in the second place the arrangement
of rock-layers is made more clear by the means of
these very fossils.
A geologist, looking at the rocks in America, can
say which there were first-formed, which second-
formed, which third-formed. Also, looking at the.
rocks in England, he can say which there were first-
formed, second-formed, third-formed. He would, how-
ever, find it very difficult, if not impossible, to say
which among any of the American rocks was formed at
about the same time as any particular one among the
English rocks, were it not for the help afforded him
by these fossils.
Just as the: regular succession of rock-strata .his
been gradually learnt, so the'egtlar succession of dif-
ferent fossils is becoming more and more understood."
It is now known that some kinds of fossils are always
found in the oldest rocks, and in.them only; that some
kinds are always found in the newest rocks, and. in,:
them only; that some fossils are rarely or never found,,
lower than certain layers, that some fossils are rarely
or never found higher than certain other layers.
So this fossil arrangement is growing into quite a-
history of the past. And a geologist, looking at
certain rocks, pushed up from underground, in
England and in America, can say: 'These are very
different kinds of rocks, it is true, and it would be:
impossible to say how long the building up of the one
might have taken place before or after the other. But
I see that in both these rocks there are exactly the
same kinds of fossil-remains, differing from those in
the rocks above and below. I conclude therefore that
the two rocks belong to about the same great age in
the world's past history, when the same animals were
living upon the earth.'
Observing and reasoning thus, geologists have
drawn up a general plan or order of strata; and. the-
whole of the vast masses of water-built rocks through-
out the world have been arranged in a regular suc-
cession of classes, rising step by step from earliest
ages up to the present time.
First there are three grand divisions:
I. PALEOZOIC, OR ANCIENT-LIFE ROCKS;
II. MESOZOIC, OR MIDDLE-LIFE ROCKS;
III. CAINOZOIC, OR NEW-LIFE ROCKS.
These, with their chief sub-divisions, are given in a
short list at the close of the chapter, beginning with
Below the Ancient Rocks lie what some suppose
to be the First-formed Rocks, beyond which we know
In a general way this classification will serve
wherever geology is studied. Some geologists arrange
differently, but the variations are slight. In certain
countries some of the classes or sub-divisions may
be entirely lacking, yet the order kept will be the
same. The Devonian may be absent, but if present,
you will never find it under the Silurian, or above the
Carboniferous. The Cretaceous may be missing, but
if there, it will not lie beneath the Triassic or over the
Miocene. So also with others.
The following list of names should be from time to
time carefully referred to, in the course of reading
Part II. of this book.
TABLE OF STRATA.
AzOIC, OR NO-LIFE ROCKS.
PRIMARY, OR PALEOZOIC, OR ANCIENT-LIFE
3. Silurian Age of Lower Anmals.
4. Devonian.-Age of Fishes.
5. Carboniferous.-Age of Coal.
SECONDARY, OR MESOZOIC, OR MIDDLE-LIFE
I. Triassic ,
Jurassic }Age of Rep tiles.
2. Jurassic I
3. Cretaceous.-Age of Chalk.
TERTIARY, OR CAINOZOIC, OR NEW-LIFE
2. Miocene t
2. Miocene Age of Mammals.
Post-Tertiary, or After Tertiary (Including Age
*Literal meaning-" Dawn-New." t L "Less-New."
"Where wast thou when I laid the foundations of the earth ?
declare, if thou hast understanding. Who hath laid the mea-
sures thereof, if thou knowest ? Whereupon are the found-
ations thereof made to sink? or who laid the corner-stone
thereof ?"-JOB xxxviii. 4-6. (marg.)
IT is said that the whole of the Stratified Rocks
forming the earth's crust, amount altogether to about
twenty miles in thickness.
This only means that if you could take each
stratum at its thickest part, and arrange it in its
place with all the rest above and below, not one of
the whole series being left out, the depth of the
entire mass would probably be about twenty miles.
In the same manner the stratified rocks of Great
Britain are said to be over nine miles thick, though
in no one spot does their depth approach this amount.
For nowhere in Great Britain, or in all the world,
are all the different rocks found together at their
greatest thickness. Where one kind is thick, another
beneath it is thin, and other rocks are altogether
wanting. Sometimes several of the uppermost have
either been never formed there, or they have been
washed away since formed.
Under New York these rocks are said to be about
two miles and a half thick, and in Pennsylvania at
least seven miles. On the Continent there are, it
is believed, not much less than five miles of strati-
fied rocks, without counting the lower primary
layers. So the depth varies greatly in different
But if we realise that these vast masses have been
al. built up, as it seems, under the ocean, grain by
grain, or bit by bit, or shell by shell, of sand or earth
or animal remains, we shall find the amount to be
*These rock-strata give us a 'chain of records' of the
past,, but the chain is broken in many places, and
many links are wanting. At the best, the history is a
fragmentary one, with great gaps and sudden jumps,
and chasms which the geologist has no power to bridge
over except by guesses.
-o c- .-O
CHART OF STRATA.
-r I-- --1-
-4 -W- -
-~ -."-; --; ar~-
Rock- Bend'itgs. 63
SOne great difficulty in reading geology arises from
the fact that it is a volume which is being written
chiefly out of our reach. Dry land remains from cen-
tury to century unchanged, except through the yearly
loss of its material, stolen by frost and rain, rivers and
sea-.and how great this loss is few know. But dry
land receives no additions as a rule. All the building
,up of new land goes on under the ocean.
It would be an immense advantage to the student
ifhe.could .occasionally take. a walk under the sea, so
as to be able to note, not- only the carting away of
material from dry land, but the building up of that
,material into new land beneath water. For it should
-be:.clearly understood and remembered that every yard
:of:.freshimud or rock formed by the sea is made
entirely out of material stolen from the land. This
double work of taking away from the land and laying
.down upon the ocean floor goes on incessantly; but
only one half of it can we see.
And indeed, even if we could so walk under the sea,
like Southey's Kahama, it would avail us little, unless
we could. watch through long periods of time, with
'unfailing patience, to see the slow and gradual growth
of, the: building. .And were this too possible, we
;should still.stand in need of some power to enable
us to look into,. the..far ..dim past, and to see -the
64 Rock- Bendings,
precise manner in which this work was then carried
For although the manner of rock-making was then
probably much the same as it is now, we have no
power to speak positively in the matter. It may have
taken place exactly as it now takes place, or various
causes may have combined to make both the pulling
down and the building up very much more rapid
than they are at present. It is easy to conjecture
one way or another, but we cannot know which really
was the case.
The words 'stratum' and layer' have been .used
often in the last few chapters. Although their mean-
ing is much the same, yet each has its own distinct
A 'stratum' may consist of a great many layers.'
In a stratum of limestone there are generally.several
thin layers of limestone one over another, making up
the whole mass or stratum. So also a stratum of
coal consists of few or many layers of coal. The
Slayer' may be either thick or thin, and it may be
either loose or joined to the next layer. The
stratum' means the whole mass of one kind of rock,
lying between two beds or strata of other kinds of
rocks--strata being the plural of stratum.
Suppose you had a great pile of paper, first a
number of blue sheets, over them a number of white
sheets, then a few pink sheets, over them a number
of white sheets again, then a few green sheets.
Each sheet would picture a 'layer,' but each supply
of one colour lying close together would picture a
A 'formation' means the whole set of strata be-
lieved to belong to one particular age or part of an
age in the past. Rocks of different kinds, in different
places, if containing the same kinds of vegetable and
animal fossils, are said to belong to the same 'forma-
Rocks are not commonly found, as they were first
built up, in flat layers. Sometimes they are bent,
curved, slanting; sometimes pushed into an upright
position; sometimes for a short space even turned
quite upside down, so that a top stratum is seen for
a short distance actually underneath a lower and
earlier-formed stratum, with plain marks of the catas-
Sometimes it is found that the lower rocks are
crumpled, and bent, and distorted, while over these lie
some perfectly smooth flat layers. This shows that
the disturbance of the lower rocks must have taken
place before the upper layers were dropped by the
sea. After some great sudden upheaving, or some
slow crushing together of the rocks, a calm time fol-
lowed under the ocean, and sand or earth layers were
quietly formed, afterwards not to be bent or broken
by the gentle uplifting of that sea-bottom out of the
It seems strange to speak of rocks being bent.
But under tremendous pressure even the hardest
rocks will yield, curving and folding like soft clay.
Also many rocks are known not to be so hard as we
commonly see them, when buried underground and
sheltered from the air.
Anyone who has been through some of our great
iron-working manufactories, and has seen how cold
iron can be cut and pierced, twisted and bent, by the
deliberate exercise of great force, will wonder less at
the effects of pressure on rock. Many of these dis-
turbances past were doubtless calm and gradual,
though others must have been sudden and startling-
even as now, gentle and slow forces work side by side
with fierce and terrific ones. More of this later.
On one of the arms of the Lake of. Lucerne, as the
tourist goes by steamer towards the little village of
Fluellen, he may note a remarkable instance of this
rock-bending, in the cliffs to the left. It is in one
part as if a gigantic hand had grasped the smoothly
lying rock-layers, and had deliberately crushed them
into a variety of fantastic crumplings, as a man might
crush a piece of paper in his fingers.
Rock-foldings vary in size from tiny bends an inch
in depth, to great' wrinklings or creasings of the
earth's crust, extending through miles of country.
Many a range of mountains is an example of such
huge wave-like bendings, each crease or wrinkle,
divided by a hollow from the next, being thousands of
feet in depth.
If no after-change took place, it would be possible
to trace in unbroken continuance the lines of the bent
layers, running up each mountain and down each
hollow. Take half-a-dozen pieces of thick cloth, and
fold them backwards and forwards into several
massive plaits, to make the matter more clear. Each
piece of cloth rising and falling through the bends
will picture a layer rising and falling through the
But in reality the upper layers cannot be so traced,
for mountains do not remain unchanged. Frost and
rain, wind and torrent, glacier and avalanche, are ever
pursuing their work of destruction. The mountains
are lower now than they were a hundred years ago,
for they are incessantly losing a part of their material.
Loose soil is washed away, stones are carried off,
crags and precipices crumble and break, and gradu-
ally whole masses are swept from the exposed
summits, leaving bare those underlying rocks which
still are buried low on the more sheltered mountain-
Some chapters back I spoke of the slips and
sliding likely to take place in the upper stories
of a house, in consequence of lower-story altera-
Now these slips and sliding have actually taken
place in the earth-crust. As the mountains were
upheaved, and as low-lying plains were lifted higher-
whether by slow or sudden action we cannot always
know-there were often slips or displacements in the
various rocks disturbed by such movements. These
slips are called faults, both by geologists and by
miners. A 'fault' is found when a mass of rock;
containing sometimes several different strata, has
slipped down to a lower level than the rocks adjoin-
ing, so that each layer is separated from what was
once a continuation of itself in the other mass.
These 'faults' may be a matter of a few inches or
of hundreds of feet. Such a fault in a coal-mine, if
extensive, is a serious matter, for the seam of coal
will suddenly cease, and will have to be sought for
elsewhere. The rocks adjoining having slipped down,
in consequence of deep underground disturbances,
the continuation of the coal-seam will lie lower
'He cutteth out rivers among the rocks.'-JoB xxviii. io
IN pieces of rock there are found often curious
markings, telling each its little tale of bygone days.
Sometimes a bit of sandstone is dented over with
small round holes or pocks, one here or there breaking
into the rim of its next neighbour. These are traces
of rain-drops which fell long long ago. Such mark-
ings may be seen upon the sand of the sea-shore,
commonly remaining only a short time because washed
away by the next tide or shower. But in certain
cases the sand has been left undisturbed to retain the
traces < the last shower which it received in its soft
state, before hardening into rock.
Or again a piece of sandstone may be seen to have
softly-rounded furrows, running from one end to the
other. Here again are water-marks. Did you never
note how the retreating tide leaves often upon the
sand tiny ridges and hollows side by side, which the
next tide smooths away only that fresh ones may be
formed? These ridges are caused by the movements
of the waves. After a storm they are of a larger size;
and it is said that on the Goodwin Sands they are
often two feet or more in height. Hardened sand-
stone sometimes bears these wave-marks, which were
imprinted upon it when soft.
Again, stones are sometimes found, curiously
marked with lines, as if they had been polished and
scratched, not anyhow and in all directions, but in a
regular way. Sometimes one set of lines will run
across another set, or there will be deep scoring in
the midst of delicate even lines, but as a general rule
these scratching all lie straight along the greatest
length of the stone. Such stones exist in great
numbers, and they were long a serious puzzle to
geologists. Even now there is not absolute certainty
as to the real cause, though the last and generally
believed explanation seems most likely to be the true
If you were taking a walk in Scotland, you might
be struck with the appearance of certain oft-recurring
loose gravel and sand patches, or masses of rugged
stones and clay, or heaps of loose rocky debris. They
do not lie on the higher mountains, but abound in
plains and valleys. If you could examine a very little
way underground, just below the surface layers of
earth or gravel, you would find this unstratified
deposit of clay and rough rocky fragments reaching
through miles and miles of country; not only in Scot-
land, but also in many parts of Europe and of North
America. It is never, however, found further south
than 40 and 50 degrees North Latitude. The same
rough unstratified deposit is found in countries of the
southern hemisphere, but there in like manner it is
not seen further north than 40 and 50 degrees South
Latitude. So whatever is the cause of this singular
appearance, it plainly has nothing to do with tropical
The deposit is made up chiefly of sand, clay, and
stones, sometimes a very stiff kind of clay, with
large stones and boulders scattered all through it, and
this in Scotland is called till. Sometimes there is a
layer of such boulder-filled clay, and then a layer of
sand, and then more clay, not so coarse and stiff in
character. But the clay is never really stratified, and
the stones and boulders are always scattered pell-
mell through it. Another name by which it is
known is 'boulder-clay, and yet another is drift. In
places it is as much as fifty or a hundred feet in
The stones and boulders are found as a rule to have
been broken off from the rocks and mountains in the
neighbourhood. This is easily seen, by comparing
the rock of which they are made with the rocks of
which the mountains are made.
It is stones found in this clay, and in the heaps of
loose debris, which are so curiously polished and
scratched. They are of every size from tiny pebbles
up to huge blocks, and the markings are of every kind
from the finest lines to deep-ploughed furrows.
Not only are loose stones thus marked, but large
spaces of rock in the same neighborhoods, bare of
earth and sand, will be found to be in a like manner
polished and scratched and grooved.
The course which seems to be followed by these
stones and rock-markings is somewhat singular. It
will run often in the line of larger valleys ;.but small
valleys, seem to have been ignored or rather taken at
right angles, and hills of moderate size have proved
In addition to the stones and rocks scattered
through the 'till,' there are very remarkable blocks
of stone often seen, not only on low plains but
perched upon high mountains, far away from any
74 Ice- Work.
other rocks of a like nature. They are called
erraticc' from the erratic way in which they seem
to have journeyed across wide tracts of country and
crossed deep valleys before reaching their present
resting-places. Erratics exist by thousands in the
same countries where the drift is found, but they are
never seen in the tropics. They too are often
polished and -cored on one side, like the smaller
On the Jura Mountains of Switzerland the heaps
of stones, polished rock-surfaces, and scratched
pebbles, are seen in abundance. Also, great rock-
masses are found lying there, perfectly different in
material from that of the Jura Mountains, but agree-
ing with that.of the Alps some fifty miles distant.
Now, what power could have borne those blocks,
some of them as large as a cottage, not only across
fifty miles of low grounds, but up the steep sides of
the Jura ? What power also could have carried
these multitudes of rocks and stones, polishing them,
scratching them, grooving them, mingling them with
clay and earth, and scattering the whole mixture in
lavish profusion up-hill and down-hill through hun-
dreds of miles of country ?
One of the early names by which the boulder-clay
was known was Diluvium or Diluvial Soil. The
MAGNIFIED SPECK OF EARTH. SCRATCHED STONI.
name sprang from the idea that a great flood might
have caused the deposit. Some thought that a flood
of mud had burst over the continents, bearing rocks
and stones before it in confusion. Some spoke of
an ocean-flood, and of mighty waves sweeping mud,
pebbles, and rock-boulders down valleys and up moun-
tains with resistless force. That water has consider-
able carrying power is shown by mountain-torrents.
The thought of the flood in the days of Noah
rises naturally to mind in connection with this
subject. In that vast rush of water over the land,
when 'all the fountains of the great deep were broken
up,' what might not have been accomplished?
It is well to bear the thought in memory through
the study of geology. Great changes probably did
then take place; and much of the broken and con-
fused condition of the upper rocks and soils, which
adds to the perplexities of the geologist, may be
owing to that comparatively recent event.
Still, no mere flood of water, however great, could
account for the polishing and marking of thousands
of stones and rocks in so regular and systematic a
manner. Water will wash stones together, wearing
off corners, rounding and rubbing them down, but it
will not mark angular stones from end to end with
sets of neat lines and grooves. Also, no ocean
billows, however mighty, could carry granite boul-
ders across miles of country and lift them up to
heights of hundreds and thousands of feet. Both
water and mud are utterly incapable of such a task.
In the higher mountains of earth there is a perpetual
collection of snow-a vast amount, never melting
more than slightly at the surface, and constantly
receiving fresh additions.
Now, if the snow had no means of parting with
its extra quantities-if it were always taking to itself
new supplies and never giving any supplies away, it
would increase to an enormous extent. The snow-
line, or boundary of perpetual snow, instead of
remaining at about the same height year after
year, would gradually creep lower and lower down
But there are modes of relief for the over-laden
mountain. The surface of the snow slowly evaporates
or dries away in the sunshine. Every year the
summer-heat thaws great quantities of snow in the
lower mountain regions, filling rills and torrents
to overflowing. Also great masses of loose
snow break away from time to time and rush
down the mountain, thus lessening the weight
Nor are evaporation and thawing and avalanches
the only outlets provided.
The great load of snow on the mountain-summit
squeezes the lower layers of that snow into solid ice.
For ice is of the same nature as snow, only with the
particles packed more closely together. The ice thus
formed is then pressed out by the same weight from
beneath the mass above, and creeps quietly down
through the nearest valley. This long tongue of ice,
coming from under the snow, and never stopping till
it reaches so low down the mountain-side that its
further progress is checked by constant melting, is.
called a Glacier. It is, in fact, a frozen stream-a
river of ice. Every lofty mountain which keeps a.
large amount of snow on its summit all the year
round, has its glaciers.
Some glaciers, especially those in the icy regions of
the far north, are very large, many miles in length,
and miles in width. There are also large glaciers in
the higher mountains of Switzerland. A glacier is;
like a river in many respects, but the quickest motions
of a glacier are very slow, compared with the most
sluggish of rivers. You might stand for hours by one
and never see it move; for the ice creeps along its
rocky bed at the rate of only a few inches a day-
sometimes as little as one inch, never more than fifty
inches. One mile in fifteen years is a very good pace
for glacier ice.
Yet the real wonder is, not that these great masses
of solid ice should move slowly, but that they should
move at all.
As the ice-river crawls onward, its surface is per-
petually cracking, and the cracks or chasms or cre-
vasses vary in size from a few inches to hundreds of
feet in width and depth. The cracks are commonly
across the bed of the stream, not up and down it.
They generally come when a sharper slope in the
ground puts a strain upon the ice; and later, when
the bed becomes more level, the cracks close up and
heal or freeze together again.
There are commonly down both sides of a glacier
long trails of stones and rock-fragments, which are
called moraines. Sometimes one or two or more
moraines are seen down the middle of the glacier
also. Those at the side are fed by fragments falling
from the cliffs. Those in the middle are supplied by
some other glacier which has joined the first.
Such rock-fragments, if falling into a river, would
be ground up into river-detritus-rounded pebbles,
sand and mud-and carried out to sea. Falling on
the solid ice of the glacier, they are borne slowly
down the mountain-side, till the ice reaches the spot
where it melts, and there they are dropped in a heap
called a terminal moraine.
Many of the rock-fragments fall into the crevasses,
and find their way to the bottom. There, with a vast
number of other fragments, torn by the ice from the
rocky bed, they are dragged slowly along; and as
they move, they scratch and polish the rocks below,
and are in their turn scratched and polished by those
same rocks. A great many are ground into powder,
thus thickening the turbid stream which commonly
flows beneath a glacier, during at least part of its
course, and rushes out at the terminal moraine.
Numbers of these scratched and scored stones may
be found in a terminal moraine; and if a glacier could
be removed from its bed, the rocks beneath would be
found throughout its course to be marked in a like
It is believed that in olden days, there were glaciers
far lower down the mountains, and farther south and
wider spread than now-huge glaciers in England,
in Scotland, in Switzerland, in France, in other parts
of North Europe, and in North America, such as now
are only found in ice-bound lands like Greenland.
For the marks on rocks and stones, together with
other signs in those countries, seem plainly to agree
with the marks of glaciers as seen in the present day.
There was, indeed, another explanation offered,
which for a while held sway, before the glacier-theory
came into life.
It was agreed that no ocean-waves could lift vast
blocks of granite to mountain tops, or could mark
thousands of stones as we see them marked.
But what about icebergs ? What if once the conti-
nents lay deep under water, and icebergs from the
frozen north, floating southwards on the sea, dropped
fragments of rock and stone here and there on the
submerged land, afterwards to be upheaved and to
become dry land once more? Might not the same
icebergs, grounding here and there in shallower water,
scratch and groove the rocks and stones below ?
That icebergs do in the present day bear away great
pieces of rock and drop them upon the ocean floor
is a well-known fact. An iceberg is only a huge
fragment broken off from the foot of an enormous
glacier; and the rocks and stones lying upon the
glacier, or embedded in it below, will in like manner
lie upon or cling to the ice-masses, which break off
and float away from the glacier. As the iceberg
reaches a warmer atmosphere and melts away, such
rocks and stones must sink to the bottom of the
But though this may account for some particular
blocks, it will not account for all. Neither will it
account for the marked stones. An iceberg grounding
might make with its jagged bottom deep scoring and
furrows here and there in the underlying rocks, but it
could not polish and delicately trace with fine lines
thousands of small stones.
We must, therefore, return to the glacier theory, as
that which at present seems certainly the most likely
For in Scotland, and other countries, we have the
polished rocks, the scratched and furrowed stones, the
piles of moraine-like debris. We have also the huge
blocks perched at great heights, where no water could
have carried them.
But 'these glaciers of olden days, if indeed they
existed, must have been of enormous extent. They
must have covered a great part of Northern Europe.
In North America they must have reached to a height
of three or four thousand feet up the mountain-side,
for the placing of the massive blocks there seen.
Scotland must have lain buried beneath one vast
glacier-system, branching in all directions.
Sometimes in Switzerland certain smoothed and
rounded rocks lie near together, called roches
moutonies, from their likeness to a sheep's back, and
known to have been thus shaped by the grinding
82 Ice- Work.
.,power ;of ice. Such .,rocks :are found in ,America,
:where no glaciers now can touch them. The rounded
summits of the Scotch mountains would seem to point
also._to.the same cause.
But how could the climate of so many countries
have thus differed in the past from our climate of
modern days ?
This we cannot tell, neither is. it needful that we
should. Many facts in Nature are plain, which yet
we are not able to account for.
A good many explanations have, it is true, been
suggested, and a good many theories started-some
wildly impossible, some perhaps possible but utterly
uncertain. Writers on this subject have, as a rule,
been very much more successful in disproving others'
notions than in proving their own.
For in truth we simply do not and cannot yet know,
either how or when there came about this great
period of extreme cold-commonly called the Glacial
Age-whether very long ago, or whether compara-
tively near to historical times; whether only once, or
whether several times repeated.