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 Part fifth: The mineral kingdo...














Title: First steps in general knowledge
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Permanent Link: http://ufdc.ufl.edu/UF00001728/00002
 Material Information
Title: First steps in general knowledge
Physical Description: 5 v. : ill. ; 14 cm.
Language: English
Creator: Tomlinson, Sarah Windsor
Clay, Richard, 1789-1877 ( Printer )
Society for Promoting Christian Knowledge (Great Britain) -- General Literature Committee
Publisher: Society for Promoting Christian Knowledge
Place of Publication: London
Manufacturer: R. Clay.
Publication Date: 1848-50
 Subjects
Subject: Metals -- Juvenile literature   ( lcsh )
Minerals -- Juvenile literature   ( lcsh )
Geology -- Juvenile literature   ( lcsh )
Crystals -- Juvenile literature   ( lcsh )
Caves -- Juvenile fiction   ( lcsh )
Bldn -- 1850
Genre: non-fiction   ( marcgt )
 Notes
General Note: "Published under the direction of the Committee of General Literature and Education, appointed by the Society for Promoting Christian Knowledge."
General Note: Baldwin Library has parts 3 and 5.
 Record Information
Bibliographic ID: UF00001728
Volume ID: VID00002
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA1827
notis - ALH9159
oclc - 04837181
alephbibnum - 002238637

Table of Contents
    Front Cover
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        Front Cover 2
    Title Page
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    Table of Contents
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Full Text













i I

N64)










FIRST STEPS


IN



GENERAL KNOWLEDGE.




PART V. AND LAST.
THE MINERAL KINGDOM.



PUBLISHED UNDER THE DIRECTION OF
THl COMMITTEE OF GENERAL LITERATULE AND EDUCATION,
APPOINTED BT THE SOCIETY FOR PROMOTING
CHRISTIAN KNOWLEDGE.





LONDON:
Printed obr the
SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE;
SOLD AT TMH DEPOSITORT,
GREAT QUEEN STREET, LINCOLN'I ININ JKLDS,
AND 4, ROYAL EXCHANGE; AND
TB ALL BOOKSELLERS.
1850.



































































LON DON

A. CLAY, PRINTS, BREAD STlEZT MILL.













CONTENTS.








THE MINERAL KINGDOM.


CoXVISATU1o91I. N n&dUroflrnsfals ............... 4- 1
II. Cbuactera vo Mlnrals-.alsllzton ...... 12
111. Fotus of Cry. -Ia- Clue'f'ne -Gases-
Water-Carboa.-The ............. 1U
IV. CouKou3ns orCAzaoN :-.Cosl-PIlubao
-Ambag-t-tumam. ........... ............. 31
V. Coupouvrs oj A BAz~ur N. oUn-1aus
otClgala-Awomola.-Nitrus of etlah
-Uaoda-CAmmon Salt-Ltue-Magas
-Alu na..... ............ ... ..... 47
VI. ISamy MgmaAjrAz: -Pon Mba, or
Quart&-Vltewullarkak-RockCrystal
Ametbys Tranducnta Varistlss -
Plntt-Aga-*@-Couussam-Onyx -Bu
domy-3st-pla at Aar ............... *44
VII. EAXSNT MlWWu8r (9a0lad) :--Quar
eavilanod-Jaspsr-B oa -lat-
atoau-Patrlaiooad--ropalUapoon
-Pot-atoms-Tale-Uarpentis.-User-
hana ............... ..................*............ 7






CONTENTS.


Pano
COnTIasITION VIII. EAITxT MtxIALs (coUetiUed) :-Asbestus
-Amianthus Hornblende-Sapphire-
Ruby Felpar- Porcelain Clay-Moon-
stone Sunstone-Alblte-Labradorite-
Potter's Clay-Garnet-Tourmallne-Mica
-Topa--Lapis-lauli and Emerald ...... 84
IX. MrTAL. :-Various Ores of Iron-Manga-
nee Nickel -Cobalt-- Zinc -Br ss-
Bismuth- Lead.................................... 101
X. MZTALS (costiu ed):-Mercury or Quick-
silver-Copper- Malachite Tin-Anti-
mony- Arsenic .................................... 16
XI. Tau NOLE METALs:-Platinum-Silver 18
S XII. TxH NOILS METALS (coaclnded):-Gold... 168











FIRST STEPS IN GENERAL KNOWLEDGE.


PART FIFTH.

TiOe Mineral Bingbom.


CONVERSATION I.
NATURE AND USEM OF XMIZ ALS.

ONE cold winter evening, when snow was fall-
ing fast, and the keen north wind moaned in the
chimneys, and drove the icy shower against the
casement with a grating sound, a merry little party
had gathered round the Christmas fire, little
regarding the state of the weather, or thinking
of it only with concern for those who had not
a warm and happy home like their own.
Up to that time the weather had been unusually
mild, proofs of which might be seen in the garden
flowers still decorating the apartment, and which,
B





2 FIRST STEPS IN GENERAL KNOWLEDGE.

under the altered temperature, had a singular
appearance. Here were purple and red anemones,
clusters of pink hepaticas, a Christmas rose, and
even a double-blossomed stock, mixed with the
ivy, laurustinus, and holly which formed the cus-
tomary winter ornaments of the room.
The young folks were playing at a well-known
game, where one of the party is required to think
of some object without naming it, and the rest are
allowed to ask him a certain number of questions,
and then to guess by the nature of his replies what
that object is. When it came to Mary's turn to
guess, and when her brothers put the usual ques-
tions, Is it an animal ? Is it a vegetable? Is
it a mineral ?" she said "No" to the first two
questions, and hesitated at the third, but at last
she said No" to that also. Henry appealed to
his father to tell them whether it ought not to be
against the rules of the game to think of anything
that was neither animal, vegetable, nor mineral,
because it made it so difficult to guess.
Not only difficult, but impossible," replied his
father, "and it would be equally impossible for
Mary to think of any earthly object which did not
belong to one of those three kingdoms."





WHAT 18 A MINERAL?


Mary laughed, for she thought that when her
father knew what she had been thinking of he
would change his opinion. So she encouraged her
brother to ask more questions, and when by her
answers Henry found that the object was white
and cold, and opaque and soft, and not lasting, he
rightly guessed that it was snow.
There, papa, was I not right in saying that it
is neither animal, vegetable, nor mineral ?" asked
Mary.
Before I answer you, let me have your idea
of what a mineral really is."
I think it means any kind of stone or metal,"
said Mary.
And I think mineral means anything dug out
of a mine," said Robert.
Both right, so far as your ideas go, but they
do not go far enough. Properly speaking, every
thing in nature that has not life belongs to the
mineral kingdom."
The children looked astonished, and Henry
asked whether the hard road we walk upon, and
the dust that flies in summer, and all the earth in
fields and gardens are minerals.
They are not distinct minerals, but they are





4 FIRST STEPS IN GENERAL KNOWLEDGE.

made up of a mass of different mineral substances
mixed together."
But some of the earth is very soft," said Mary,
" without any stones at allin it: is that mineral?"
The chief portion of it is; and though it
seems strange to you to think of a mineral except
as a hard rocky substance, yet you must know that
there are different states of minerals, and that even
rocks themselves crumble away by slow degrees.
Wind and rain and frost are continually carrying
on their work of forming and bringing down this
waste from rocks and hills to the lower parts of
the earth, where, mixing with various animal and
vegetable substances, it forms the common soil."
Some of the bricks in the garden wall are
crumbling away," said Robert, "and I very often
get brick-dust on my clothes from them."
And my flower-pots crumble away," said Mary.
After they have been out in the rain a long time
a red powder comes off on my hands."
But bricks and flower-pots are made of clay,"
said Henry, and that is a sort of earth, and very
different from the rocks papa was speaking of."
It is not very different in composition from
some rocks," said his father, "for clay is nothing





NOW TO DWZU3EM DINBALU.


more than a man of grains, which, if they could
be carefully separated, would be found each to
belong to some mineral species; and so also very
many rocks are compounds of two or more minerals
closely united."
Then I suppose people who understand mine-
rals can tell what all the different rocks are made
of," said Henry.
They can: by studying first pure specimens
of minerals, and learning to understand their dif-
ferent characters, they get so well acquainted with
them, that they can recognize them wherever they
meet with them, even amongst a crowd of other
minerals which do not seem to differ from them."
"Papa speaks of minerals as if they were living
creatures," said Mary, laughingly, "and says that
people understand their characters !"
Each mineral species has a distinct character
of its own by which it can be known from other
minerals, just as each vegetable or animal species
has distinct qualities of its own, separating it from
all others. What I mean by the 'characters' of
minerals you shall know ere long."
But you have not yet satisfied our curiosity
about snow, papa," said Henry. I dare say you





6 FIRST STEPS IN GENERAL KNOWLEDGE.

will class it with mineral substances, because you
say that everything without life is mineral; but
really it seems very odd to call it so, because when
it melts, it is nothing but water."
"You will be surprised to learn that there is
nothing which can properly separate water from
the mineral kingdom. Were the temperature of
our globe somewhat lower than it is, we should
rarely see water except in crystal-like masses or
layers. And why should rocks of ice, such as the
enormous icebergs of polar seas, be less entitled
to rank with minerals than any other kind of
rocks ?"
Because they sometimes melt away, and other
rocks do not," suggested Henry.
They need not be the less mineral on that
account," replied his father. You find it difficult
to comprehend that there are different states of
minerals, sometimes solid, sometimes fluid. Ice
in becoming fluid only goes through quickly the
same process which the metals perform slowly,
when exposed to heat. If water is not to be
classed with minerals, because at the ordinary
temperature it is a liquid, the same may be said
of quicksilver."





IMPORTANCE OF MINBRAL8.


The children now remembered that they had
seen several of the metals in a fluid state, especially
lead, some of which Henry had melted down, and
had poured out like water. Mary also recollected
trying in vain to lift a bottle of mercury or quick-
silver, which her papa was using, and which he
called a metal, although it was always liquid.
A drop of this mercury falling on the table had
separated into a number of smaller drops, each
being a perfect globe, and shining like silver.
They therefore began to understand that minerals
may not only be hard like rocks, but crumbling
or soft, like sand or clay, and fluid like melted
metals, and even clear and limpid like water.
Minerals are much more useful than I ex-
pected," said Henry. If the earth in fields and
gardens is a collection of minerals, then plants
could not grow without them; and if water is a
mineral, then we could not any of us live without
the mineral kingdom."
The animal and vegetable kingdoms are, in-
deed, dependent in a wonderful manner on the
mineral kingdom, which, itself without life, growth,
or feeling, has been made the great means of sup-
porting life in nature."




8 FIBT STEPS IN GENERAL KNOWLEDGE.

Does nothing grow in the mineral world ?"
asked Mary.
There is no proper growth, though there is
increase," said her father.
And what is the difference, papa, between
growing and increasing ?"
The power to receive food is the grand dif-
ference. The food of the tree is obtained from the
ground and from the air, and inthe form of sap circu-
lates through every part, and deposits solid matter,
thus causing growth; and the food of animals causes
the formation of blood, which, in like manner,
circulates through the body, and deposits solid
material for the growth or repair of the whole
frame: but a stone has no power to take food,
and therefore no such circulating fluid; and if it
increases in size, it is from some external cause,
and not from any internal growth."
Henry here repeated what he had lately read,
that, in the labyrinth of Crete, a great many names
of visitors were once cut in the rock, and now,
instead of being hollowed out, the letters are filled
up, and the names project, as if the stone in these
hollows had grown since the carving was done.
His father told him that if this anecdote be true,





STALACTITES.


we can only suppose that water, trickling into,
these hollows, has deposited mineral substances,
and so filled up the cavities, in the same way that
in caverns the water which drips through the roof
often deposits small quantities of carbonate of
lime, until a small knob or wart of this substance
is seen on the roof of the cavern; and this wart,
in the course of time, lengthens into a tapering
cylinder, called a stalactite.
So those beautiful stalactites we have heard
of, are all made in that simple way !" said Mary.
" In Austria, there is an immense cavern, with all
sorts of curious stalactites in it; and mamma says
that some are like pillars, others like pulpits and
thrones; and there is one that rings like a bell,
and another that spreads across several yards, like
a curtain, and is beautifully transparent."
It is the grotto of Adelsberg," said her father,
" the most extensive grotto in Europe, having a
long suite of chambers, adorned as you describe.
Once a-year, the peasant lads and lasses, for miles
round, come to dance in the largest of these
caverns; and the sounds of music and laughter
are then heard in those gloomy caves, which other-
wise echo only to the constant drip of the waters
which produce all these wonders."




10 FIRST STEPS ON GENERAL KNOWLEDGE.

It must be a damp place to dance in, with
drops of water falling on all sides," said Mary;
" but I suppose the peasants do not wear very
thin shoes."
It must look like a palace of ice," said Henry;
" but it is much better than ice, because it does
not melt away."
Robert inquired whether there had ever been a
palace made of ice; and he was told of the beau-
tiful edifice once constructed of that perishable


INCLINED ICEBZRO.
material, by the Empress of Russia. The snow-
huts of the Esquimaux were also described to him,





ICBBmGM 11

to show that, in cold countries, snow is employed
for really useful purposes, and forms a compact
and solid mass, very different from the fleecy heaps
which lie for a time on our fields. A picture was
also shown him of one of the massive tabular ice-
bergs seen in the Antarctic seas.
After this, the children were better reconciled
to the idea of ice and snow belonging to the mine-
ral kingdom; and when their father had concluded
his conversation with them, Mary found a descrip-
tion of the palace of ice in Cowper's Task,* and
read it aloud to her brothers.
The Winter Morning Walk."









CONVERSATION II.
CHARACTERS OF MINERALS-CRTSTALLIZATION.

EARLY the next morning, Mary was busily
employed in making a small wire basket, which
she said would be in a short time very beautiful;
but her brothers could see nothing to admire in
it, for it was a mere rough frame-work; and when
Mary had brought it a little into shape, she wound
threads of common white worsted round the wires.
They therefore began to laugh at her performance,
but she told them to wait a few hours, and they
would see a beautiful sparkling basket, fit for the
drawing-room table.
The truth was, that Mary had been learning
from her mamma the way to make alum baskets,
and was encouraged to put her knowledge to the
trial, by a promise from her papa, that if she suc-
ceeded in making a good basket with large crystals,
he would tell her more about crystals, and show
some experiments.
She therefore asked for a deep basin, and





CRYSTALLIZATION.


poured into it twice as much hot water as would
have been sufficient completely to cover her little
basket. Into this water she then put some
pounded alum; and she continued to put it in
until the water would not dissolve any more alum.
Then she carried this basin of strong alum water
into the kitchen, and asked the cook to let it boil
gently. But when the cook was about to pour it
from the basin into the saucepan, Mary had a
piece of thick fine muslin ready, through which
she filtered the alum water. It was now allowed
to boil until nearly half of it had boiled away.
Then Mary suspended her little wire basket in
the basin by a thread, across the top, and putting
the basin on the floor in a dry place, she poured
the hot alum water over it, and begged that it
might be left quite still, because, if it was dis-
turbed, the crystals would not form properly.
Mary went frequently to look at the alum
water, and at last she saw what looked like a little
speck of ice on the surface, showing that crystal-
lization had begun. She could not help taking
out this first tiny crystal, and admiring its shape;
for it was a beautiful and perfect eight-sided figure,
with sharp points. It was not until the next





14 FIST STEPS IN GENERAL KNOWLEDGE.

morning that she found the basket wholly en-
crusted with crystals, and then she carried it in
triumph to her father.
These crystals of alum," said her father, will
afford a lesson on the characters of the mineral
kingdom. Tell me what you see in them."
They are bright and transparent," said
Henry.
They are heavy and hard," said Robert.
And they have a very powerful taste," said
Mary.
Yes; and these are some of the common cha-
racters by which we describe minerals, though it
is not often that we can say they have taste. People
may learn much about minerals by attending closely
to their weight, hardness, lustre, colour, and other
obvious characters; but they may learn very much
more by studying the forms of crystals, and by
watching the action of heat and of acids on various
mineral substances."
Crystals seem to be of all sorts of shapes,"
said Henry.
And yet," rejoined his father, each mineral
has its own distinct system of forms; and these
crystals of alum, which seem to you to be so irre-





ALUM CRYSTALS.


gular, are all made after the same pattern, which
is of a shape called an octahedron,* or
having eight faces, thus:"-
The children looked at the figure
their father drew on a slate, and then \
looked at the alum basket, but they
could not find any crystals that exactly resembled
the one he had drawn, although Mary imme-
diately recognized it as the shape of the little
crystal she had found floating separately on the
water. He explained to them that it was not
to be expected in a mass of crystals, that any
one should be found sufficiently distinct to show
its exact shape; for, in the process of cystalliza-
tion, or becoming solid, the crystals had interfered
with each other, and overlapped each other, some
not having room to take their natural shape, and
others being free to enlarge in one direction, while
they were pressed and confined in another.
Mary thought it must be very difficult to find
out the true shapes of crystals; and she asked
whether there were many other shapes besides this
eight-faced crystal.
The variety is so great," replied her father,
From the Greek oto, eight, and hedra, face.





16 FIRST STEPS IN GENERAL KNOWLEDGE.

" that it is one great cause of the beauty of a col-
lection of minerals; but the difficulty of distin-
guishing the different forms is greatly lessened by
their arrangement into regular systems, just as the
objects in the animal and vegetable kingdoms are ar-
ranged according to their most striking characters."
I saw whole rooms full of beautiful minerals
at the British Museum," said Henry; "but I
suppose their history is too difficult for us to
understand."
"It is, indeed, a subject that you cannot go
very far in; because, in order properly to under-
stand the composition of minerals, the use of an
instrument called a blow-pipe is absolutely neces-
sary, and this I do not think it desirable for you
to meddle with at present."
"What is a blow-pipe?"
The simplest kind of blow-pipe is merely a
bent tube, ending almost in a point, and having at
the small end an opening not larger than a pin-
hole. By placing the small end in the flame of
a lamp or candle, and blowing through the tube,
the flame is concentrated upon a small portion of
the mineral whose qualities are to be ascertained.
The effect of heat on different minerals is thus





CHARACTERS OF FUNERALS.


seen, while in certain cases, powerful acids, such
as the sulphuric, muriatic, and nitric acids, which
you have seen labelled on my shelves, are em-
ployed to decompose minerals. It is extremely
interesting to see some minerals melting under
the blow-pipe, others evaporating, others resisting
the heat; and also to observe the effervescence of
certain minerals when tested by acids, and the
jelly-like substance to which others are reduced
by the same means. All this must be placed
among the pleasures in reserve for you, when
you, Henry and Robert, have enough steadiness
of head and hand to perform the experiments for
yourselves, and when you, Mary, have enough
knowledge of the subject to understand and enjoy
the sight. From what I have said, you will per-
ceive that there are three ways of discovering the
characters of minerals, and of distinguishing them
one from another. Perhaps each of you can tell
me one of these ways?"
One way is," said Mary, "by taking notice of
their weight and colour, and hardness and lustre,
and taste, if they have any."
"And a second way is to find out the shape of
the crystals," said Robert.





18 FIRST STEPS IN GENERAL KNOWLEDGE.

And a third way is," said Henry, "to get a
blow-pipe and see what effect the heat of a flame
will have upon a mineral; or to use strong acids,
and find out what they will do to it; and when I
am older, I am to try these experiments myself."
And so am I," said Robert; "and Mary is to
look on."
Mary's department," said her father, "must
be that of getting crystals of various substances,
and thus showing you the variety in their forms."
Can I get any other crystals besides those of
alum," said Mary, delighted to find that there was
to be employment for her, although she was shut
out from the use of a blow-pipe.
"You may crystallize salt, sugar, and some
other substances, and you may vary your alum
baskets by colouring the solution with indigo,
verdigris, or lamp-black, according as you wish
blue, green, or black crystals."
How I long to set about it!" said Mary, her
eyes sparkling with joy.
"There is a very simple way of causing the
formation of crystals," said her father, by which
your impatience may be gratified at once. Look
at the window-panes covered with the curious





HOW TO PRODUCE CRYSTALS.


frost-work of winter. A wonderful assemblage of
crystals has there been formed from the moisture
on the inner part of the window. But if you
wish to see the process actually going on, breathe
on one spot of the window for a second or two,
and then watch the effect."
Mary hastened to breathe on one of the frozen
panes, and soon the frost-work melted entirely
away from a round space, about the size of a half-
crown; then, at her father's bidding, she stood a
little back, so as not to let her warm breath inter-
rupt the freezing which was to follow. In a few
minutes she was delighted to see little needles of
ice shoot from the sides of the space towards the
centre, and after a time the whole space was
covered, but with larger crystals than those on the
rest of the pane. Asking the reason of this, she
was told, that when crystallization takes place
rapidly, the crystals are small, when slowly, they
attain a larger size. Also, that when crystallization
begins at myriads of points at the same time, there
is not room for the enlargement of the crystals;
but when a space is open such as that caused by
removing the ice from the windows, then the re-
maining moisture has room to form larger crystals.





20 FIRST BTEPS IN GENERAL KNOWLEDGE.

"That marble' bust," said her father, is an
instance of a mass of crystalline grains so densely
crowded together that the eye cannot detect
them."
The children looked at the bust in amazement,
scarcely believing that the pure white substance,
so smooth and solid, could have been crystallized.
Having seen by the frozen moisture on the window,
and by the making of the alum basket, that crys-
tals are formed when a mineral changes from a
liquid to a solid state, they now began to under-
stand that once upon a time the very marble itself
must have been liquid.
Whenever a liquid becomes solid," said their
father, "there is actual crystallization, but it
depends upon circumstances whether the crystals
shall be large and regular, or minute and irregular.
If we take a hot solution of sugar, and set it away
to cool, we shall get crystals on the bottom of the
vessel, or on a thread or twig which we may put
into it; but you all know that by another mode of
crystallization sugar is reduced to a solid mass, as
in this lump of sugar. Here you see, indeed, a
crystalline texture more clearly than you can in
marble, but you are equally unable to make out





VARIITIES IN CRYSTALLIZATION.


regular forms. If we melt a quantity of sulphur,
the surface on cooling will first become solid, and
almost without any sign of a crystalline texture;
but if we break this solid crust, and pour away
the liquid part within, the sides of the vessel
when cool will be covered with crystals like deli-
cate needles. Now this solid crust is as truly
crystallized as the needles, but there was not
room for the crystals to expand."
Henry wished to see this done, and his father
gratified him by melting a quantity of sulphur;
an experiment which he would not permit the
young people to perform for themselves, because of
the danger of allowing it to take fire. He also
showed them a very pretty experiment with iodine,
which when heated passed into vapour, but on
cooling again, the sides of the glass vessel con-
taining the vapour were covered with brilliant
crystals.
Then," said Henry, there are three ways at
least of getting crystals, and in time I hope we
shall be able to practise them all. I should never
have thought of the last way, for when once
anything is changed into vapour, we do not expect
to see any more of it."





22 FIRST STEPS IN GENERAL KNOWLEDGE.

"And yet," said his father, "it is from the
vapours, or clouds above us, that the countless
myriads of crystals are formed which now cover
the earth."
What crystals, papa, and where ?" said Henry,
walking towards the window.
"Those flakes of snow that have so thickly
carpeted our fields are composed of innumerable
crystals, some of which are regular and beautiful
in their shapes, though less striking in our lati-
tudes than in polar regions, where their distinct
forms have attracted much admiration. A few
flakes of snow are still falling; go and exar
mine some, that you may see their crystalline
form."
Henry went out into the porch, and holding out
his arm caught several flakes on his sleeve, and
although they melted very quickly, yet he had
time to discover some beautiful crystals clearly
showing themselves against the dark-coloured cloth.
His father informed him that the ice on the pond
was only another form of the crystallization of the
water.
Henry could not help remarking, that the world
seemed full of crystals. Just fancy," said he to





VASTNESS OF 799E SUBJECT.


his sister, the snowy mountains always covered
with crystals, and the miles of ice and icebergs at
the north and south poles, and then think of beds
of alum, and quarries of marble, and all the salt in
the world, and perhaps a great many of the solid
rocks and caves, where those sparkling pieces came
from in papa's cabinet." The children were in-
deed full of wonder in thinking that so many
things were once liquid which are now solid, and
they were ready with a multitude of questions,
when their father, alluding to Henry's first re-
mark, that the world seemed full of crystals,"
said-
It is ever thus when we study the works of
God. They are so vast and endless, that we grow
bewildered and confused in our ideas. When we
talked of the animal kingdom, you could think of
nothing but the myriads of insects peopling the
air, and swarming in every drop of stagnant water;
the world seemed full of them.' When we
were engaged on the vegetable kingdom, you were
equally amazed at the ten millions of sporules in a
single fungus, and at the fact that every kind of
mouldiness or mildew is a growth of these won-
drous vegetables; to you the world then seemed





24 FIUT STEPS IN GENERAL KNOWLEDGE.

' full of them.' Whatever is the present object
of study, if it is a work of God and not of man,
keeps continually growing in importance and inte-
rest, till we almost lose sight of everything else,
and become so much occupied with that one subject
that the world seems full of it.' "










CONVERSATION III.
PORMS OF CRTSTALS-OLAMIPICATIOBN-GABS--WAT- -CAIBON-
THE DIAMOND.

THE next day the boys were seen stepping briskly
over the frozen ground, and seeking among the
leafless trees for some good smooth sticks, which
were to serve as material for a lesson on minerals.
Having found some of rather a large size, they
began to make one or two of them square, by
cutting four long slices from opposite sides of each
stick. Their father required this to be done with
great exactness; so they finished their work at
home, where they could measure the breadth of
each side, and be sure of having all equal. They
spoiled some of their sticks by cutting too far on
one side, so that it was impossible afterwards to
make them square; but at last they brought two
that were tolerably exact; and Mary said they
reminded her of the stems of some plants, which
are as exactly square as though they had been
measured and cut with a knife.





26 FIRST STEPS IN GENERAL KNOWLEDGE.

How are these sticks," said Henry, to help
us in understanding the shapes of crystals ?"
I will soon show you. But first, you will be
very glad to hear, that, notwithstanding the im-
mense variety and the complicated shapes of
crystals, they are all derived from a small number
of what are called fundamental form; and it is
these fundamental forms which I hope to make
you understand something of, by means of your
square sticks. What is your idea of a thing when
it is called fundamental ?"
That it is the foundation of something else,"
said Henry.
If you saw off a piece of your stick, exactly
as long as it is broad, you will get one of these
fundamental forms of crystals, to which very many
others can be traced."
Henry had a pretty little saw in his tool box,
and he soon took off a piece of his stick very
smoothly with it; but finding he had made it a
little longer than it was broad, he shaved off a thin
slice with his knife, and made it exactly equal.
What a pretty little square of wood!" said
Mary; I wish I could cut it as evenly."
You may imitate your brother's work in





FORMS OF CYSBTALA.


something less difficult to cut," said her father.
" Square pieces like this might be cut in chalk,
raw potato, or turnip; but as each of these is more
or less objectionable for a little girl to handle, you
had better try what you can do with a piece of
stale bread."
Mary hastened to procure some bread, and began
to imitate her brother's proceedings.
I wish we had a cocoa-nut," said -
Robert, "for we could cut beautiful
little white squares out of that, and _
eat them afterwards; or a good hard
apple would do nearly as well."
This shape," said his father,
taking up Henry's square of wood,
" is called a oub (1); and I am about
to show you that many other forms
can be made from it. I now cut
off a small piece from each corner,
and you see I have already made
of it a very different shape (2); and
if I take larger slices from the same .
places, it becomes this (3); and,
finally, if I go on increasing the
slices, I reduce the cube to this (4)."





28 FIRST STEPS IN GENERAL KNOWLEDGE.

Oh, papa! that is the shape of our alum crys-
tals, our pretty eight-sided crystals," exclaimed
Mary, and she began cutting her bread very
eagerly, in the hope of imitating what her father
had done. But she found that it was not so easy
to cut the slices equally on all sides. Her brother
Henry was more successful with his wooden models,
for he had cut off several more cubes from his stick,
and after several trials, he made the three different
forms tolerably well.
He gave a large cube to Robert, and told him to
bring it gradually down to the eight-sided shape
(the octahedron); but Robert, after working at it a
long time, was so little pleased with his own per-
formance, that he wished he had not begun to cut
up that nice cube, or that he could get it back
1. again to the same shape as before.
"That you may do," said his
father, by just reversing what you
have now done, that is, by cutting
off the sharp corners of the octahe-
dron until you get this shape (1), and
then larger slices till you get this (2);
and once more till you bring it back
again to a cube, only, of course, a





GABES-WATER.


much smaller cube than before, because of the
quantity cut away.
By these simple experiments you see how one
form of crystal may be derived from another; and
I shall leave you to get familiar with these before
I proceed farther. In the meantime, if I talk to
you of minerals according to a regular system, (and
it is always best to be as systematic as we can,) I
must go back to mention the air we breathe, and
gases in general, which occupy the first class, and
which will seem to you more strange as members
of the mineral kingdom than water, which forms
the second class."
Strange, indeed," said Henry; and yet where
else could they be put, for they are not animal or
vegetable ?"
"How different this mineral kingdom is from
what I fancied," said Mary; "instead of being all
rocks, and stones, and metals, and such heavy
things, it has rivers and seas, and clouds and rain,
and ice and snow, and even gases which we cannot
see at all I"
"If gases come first, and then water," said
Henry, "what is the next step in the mineral
kingdom ? "





30 FIRST STEPS IN GENERAL KNOWLEDGE.

The third class contains carbon and its com-
pounds, to which we are indebted for the excellent
fire that cheers us on this wintry day."
Mary knew that her father meant coal, and she
began to look curiously at the knobs, in the hope
of seeing among them some sign of crystals. But
she was told that, in coal, the carbon occurs mixed
up with other substances in a massive form, but
that carbon is also to be found pure and crys-
tallized, and is then exceedingly beautiful. Go
and ask your mamma to show you a specimen of
pure carbon," said her father.
As Mary left the room on this errand, her
brothers asked her to bring the specimen for
them to look at; but Mary would not promise,
because, as she said, if it was anything like coal,
it would make her hands black.
Presently she returned, holding something in
the most careful manner, and exclaiming, "Oh,
Henry, you would not guess what pure carbon is,
if you were to think of nothing else all day.
I have only a very little bit of it in my hand, and
yet it is so precious that mamma could scarcely
trust me to bring it from her room." Then, open-
ing her hand, she displayed a diamond ring.





CARBON-THE DIAMOND.


"The diamond," said her father, "owes its
value to its extraordinary hardness and brilliancy,
and to its rarity. More than any other gem, it
reflects, and bends or refracts light; and, even
before it is polished, it exhibits electrical pro-
perties on being rubbed."
"Is this the way in which it crystallizes?" asked
Henry, looking at the diamond in his mamma's
ring.
No; the natural shape of the crystal is your
old acquaintance the octahedron, or some of the
forms that are derived from it. But diamonds are
cut in three different fashions, according to the
size and purity of the stone; and by this cutting
and polishing, their beauty and value are greatly
increased."
I wonder what they can possibly find that will
cut a diamond," said Henry. When the glazier
mends the window, he cuts out a square of glass
with a small diamond, fixed at the end of what
looks like a pencil, and he does it as easily as
I can cut this stick. Then how very hard and
sharp the thing must be that can cut diamonds."
"It must, indeed," said Mary, "for mamma
said one day that diamonds cannot be scratched,





32 FIRST STEPS IN GENERAL KNOWLEDOL

and that if people are not certain about their
diamonds being real ones, they sometimes draw a
fine file across the stone, and if it makes the least
scratch, the diamond is false; but if it leaves no
mark, the diamond is true."
"The cutting of diamonds is a tedious and
difficult task," said her father, but it is accom-
plished in several ways. You must know that
nearly all minerals separate more easily in one
direction than another; this is called their
leavage, or the direction in which they may be
most easily cleft; and it is essential to a worker in
gems to be well acquainted with this cleavage,
which is different in different stones, but always
has an agreement with the fundamental form of
the crystal. Knowing this, a jeweller would, per-
haps, be able to remove a flaw or speck in a
diamond by cleaving, or chipping off the imperfect
part; but he sometimes has the tedious task of
sawing it with a bow and iron wire, covered with
diamond powder."
Mary wished to know the use of the diamond
powder, and found that it acts as a file, and is the
principal means of cutting the gem; but that the
iron wire is cut through after being drawn five or





CUTTING AND POLISHING DIAMONDS.


six times across, and has to be continually renewed
during the progress of the work. Her father went
on to say, that, supposing the diamond to be now
free of flaws, the crystal is fixed to the end of
a stick, in a strong cement, leaving the part which
is to be cut projecting from it. Another crystal is
treated in exactly the same manner, and then the
two are rubbed together, until a facet is produced,
for so each of these various surfaces is called."
"Then the diamonds cut each other, and I
suppose it is in grinding them together in this
way, that they get diamond dust," remarked
Henry.
This is one way of procuring it; and this dust
is carefully preserved; for after the different facets
are made, a circular plate of soft iron is charged
with diamond powder, and applied in succession to
each facet, so as by its revolution to polish the
stone. Small and imperfect diamonds are also
frequently crushed to form diamond powder."
Mary wished to know what are the three dif-
ferent fashions of cutting diamonds, and her father
told her that the most costly and beautiful is
called the brilliant, and requires a very thick
stone, being nearly as deep as it is broad; the
D





34 FI8T STEPS IN GENERAL KNOWLEDGE.

next is called the rose diamond, and requires less
depth in proportion to its breadth; the third is
called the table diamond, and is used for such
fragments as are quite thin in proportion to their
breadth.


TIM BRILLIANT.


THE 1OSE DIAMOND.


SIDE VIEW.







SIDE VIEW.


Robert asked where diamonds come from, and
was told that they are found principally in India
and in South America, among the pebbles and
sand of certain rivers and brooks. He then ex-
pressed his wonder that diamonds should be
thought so very beautiful, when they have no





EXTdAORDINARY DIAMONDS.


colour; and he learnt with surprise,'that although
a pure white, or limpid diamond is what we gene-
rally see, yet there are green, blue, and rose-tinted
diamonds; and even a black diamond, which,
although without beauty, is much prized, on ac-
count of its great rarity.
What is the largest size for a diamond you
have ever heard of, papa?" asked Henry.
I believe the largest is that of the Great
Mogul, which is of the size and shape of half a
hen's egg, and before it was wrought is said to
have weighed 900 carats, which weight was, how-
ever, reduced in the cutting to 279 carats."
The children asked the meaning of the word
carat, and were told that it is the name of an
African bean, formerly used in weighing gold and
precious stones. The weight now understood by
the term carat is a little less than four grains,
troy weight; but diamonds are valued less by
weight than by the purity of the stone.
But it is time," said their father, that you
carry back mamma's ring, and you may ask her
to read to you a description of some celebrated
diamonds. The children did as they were told,
and their mother kindly read to them an account





36 FIRST STEPS IN GENERAL KNOWLEDGE.

of a famous diamond, about the size of a pigeon's
egg, which once formed the eye of a Brahminican
idol, but was stolen by a French grenadier, and
afterwards came to adorn the imperial sceptre of
Russia. Also about the smaller, but more beau-
tiful Pitt diamond, sold to the Duke of Orleans by
an English gentleman named Pitt, who was go-
vernor of Bencolen, in Sumatra; and which, on
account of its unblemished purity and brilliancy,
is considered the most perfect diamond in the
world. Also about the celebrated Sanci diamond,
which, with the Pitt diamond, and more than
fifteen hundred other brilliant, decorates the
regal sword of State of France.









CONVERSATION IV.
COMPOUNDS OF CARBON.
COAL PLUMBAGO AMBER BITUMEN.
THE next time the children went into the study,
they saw a new inkstand of a material that puzzled
them very much. It was not of bronze nor of
paper macht : it was of a smooth highly polished
substance like stone, but quite black.
"I have purchased that inkstand," said their
father, partly for the purpose of showing you
one of the less common uses of coal."
"Is it made of coal ?" said Mary in dismay,
looking at her fingers and her frock; for she had
been handling the inkstand, and expected to see
the marks of it upon her clothes.
Not of a coal which will blacken your hands,"
said her father, but of what is called stone coal,*
which has very little bitumen or mineral pitch in
it, sometimes none, and is more compact and hard
than other coals, so that it can be highly polished
and converted into these kind of articles. It burns
Anthraite.





38 FIRST STEPS IN GENERAL KNOWLEDGE.

with very little flame, but gives a strong heat, and
is largely used in smelting iron ore, and for nearly
every purpose in the arts for which charcoal was
formerly employed."
I think our coal must have a great deal of
pitch in it," said Robert, "for it is always puffing
out into a sort of black bubble which first smokes
and then blazes very much."
"You are right," said his father. The best
coal for burning in grates contains a great deal of
bitumen, and is called pitching or caking coal.
At first it burns readily with a bright flame, but
it soon forms into masses or cakes, which require
to be frequently broken asunder, or the fire goes
out. There are many varieties of bituminous coal,
and among them the beautiful channel coal, which
burns so brilliantly, and which is also used for
making boxes, inkstands, &c. Also jet, which
is still harder than cannel coal, and receives so
brilliant a polish as to be admitted among articles
of jewelry."
The children were not a little surprised to hear
that jet was of such humble origin, and Mary
began to laugh at the thought that when her
mamma was in mourning, and wore jet bracelets,





COMPOUNDS OF CARBON-COAL.


she was really carrying about pieces of coal on
her wrists.
Henry said that coal was not to be despised,
for he had heard a gentleman say that our country
would soon lose its place among the nations of the
earth if all her coal mines were to be worked out.
Is that ever likely to happen, papa ?" asked
Mary.
"It must happen in the course of ages, if our
present enormous consumption of coal continues.
But this is a very distant evil; in the meantime
we are reaping endless comforts and advantages
from its use, not only in the way of indoor con-
venience, but in the lighting up of towns by gas
from it, in the smelting of iron ore, in the working
of machinery, and in the whole system of railroad
and steam-packet communication."
Robert wished to know where the coal then on
the fire came from, and he was told that it was
obtained from the great northern coal-field, and is
commonly called Newcastle coal.
"What is meant by a coal-fld P" inquired
Henry.
The whole district where coal mines are situ-
ated is called a coal-field, and the layers of mineral





40 FIRST STEPS IN GENERAL KNOWLEDGE.

substances which always accompany the coal, make
up what are called the coal measures."
"How many coal-fields are there in England ?"
asked Robert.
In England and Wales there are three prin-
cipal districts, the northern, central, and western,
occupying many hundred square miles; the
northern includes all the coal-measures north of the
river Trent; the central includes Leicester, War-
wick, Stafford, and Shropshire; the western includes
North and South Wales, Gloucester, and Somerset."
"Is it not very dangerous to work in coal-
mines ?" asked Mary.
There is danger in all mining operations," said
her father, "for the workmen are exposed to
accidents from bad air, from the falling in of
portions of the mine, or from the bursting in of
water. But there is certainly a peculiar source
of danger in coal-mines, especially in those of our
great northern coal-field, from the escape out of
the coal itself of an inflammable gas, called car-
buretted hydrogen, but which is known to the
colliers as fre-damp. This gas, when mixed with
air in certain proportions, will take fire on coming
in contact with the flame of a candle, and yet it





THE SAFETY LAMP.


is necessary in those dark places to have a candle
or lamp of some kind. Sir Humphry Davy
invented a safety lamp, in which the flame is
surrounded with a very fine net-
work of wire-gauze, and thisgauze,
strange to say, is sufficient to pre-
vent an explosion. But unfor-
tunately the lamp gives so poor a
light, that the miners are con-
stantly removing the wire-gauze,
and thus accidents are nearly as
common since its introduction as
they were before."
The children wished they could
see a safety lamp, and their father,
taking up a pencil, soon made a
little drawing of one to gratify
their curiosity. Then directing
their attention to the pencil itself,
he said, "We have here a mineral TmE DAVY LAP.
substance related to the diamond and to coal, for it
comes under the head of carbon and its com-
pounds.'"
"Do you mean the black lead of the pencil,
papa?" asked Robert.





42 FIRST STEPS IN GENERAL KNOWLEDGE.

I do; but you must know that there is not a
particle of lead in it, and that its proper name is
graphite or plumbago. It is found in crystalline
rocks, and is itself occasionally in crystals, but
generally in masses, having a metallic lustre and
dark steel-grey colour."
I dare say it is owing to the colour that it is
called black lead," said Mary.
Henry had heard that black lead was only found
in one place in England, and his father told him
that this is true of the finest quality of plumbago,
and that the mine, which is at Borrowdale, in
Cumberland, is exceedingly valuable.
Robert wished to know how the mine is worked,
and how the black lead is afterwards fitted so
nicely into the cedar of which pencils are made.
His father told him that he would show him a
written account of it. "For," said he, "if I
undertake to describe the working and manufac-
ture of the various mineral substances, my task
will be almost endless."
"Are there any more of these compounds of
carbon?" asked Henry.
"Yes: there is the pretty yellow substance
called amber, found in irregular masses chiefly on





AMBEB.


the sea-coast, or in soil that has been deposited by
rivers. It is not unfrequent on the shores of the
Baltic."
What a pleasure it muqt be to pick up bits of
amber on the coast!" im4d Mary. "Are they
large pieces, papa, or small ?"
Generally small, but on some occasions masses
larger tan your head are met with. There is one
in the Royal Museum at Berlin, which weighs
eighteen pounds."
Henry remembered that in a lecture he had
lately heard on electricity, the name of the science
was said to have been derived from eletron, the
Greek word for amber, because amber becomes so
readily electric when rubbed. Mary wished to
know whether amber is a stone, or what it comes
from. She was told that it is a resin, and some
suppose it to be of vegetable origin, but that it
has undergone changes and admixture with other
substances while buried in the earth.
"And is it of any other use," asked Mary,
"besides for making ornaments ?"
"In Turkey it is greatly valued for mouth-
pieces to pipes. There is also an oil, called oil of
amber; and one of our finest and most transparent






44 FIRST STEPS IN GENERAL KNOWLEDGE.

varnishes is made from the carbon which remains
after the amber has been burnt. There is another
compound of carbon, which I once described to you
at some length, and which I shall therefore only
name to you now; it is bitumen, whose varieties, as
I explained to you, are naphtha, petroleum, and
mineral pitch or asphaltum."
Oh, I remember it," said Mary, "and you
read to us a curious account of a pitch lake in
Trinidad."*
"Here we leave the third class of minerals,"
said her father; "but I must remind you that
carbonic acid gas, which is a union of carbon and
oxygen, belongs to this class. Its effects in ex-
tinguishing combustion and destroying animal life
are shown in a small cavern near Naples, which is
always filled to the level of the entrance with this
gas. A lighted taper plunged into it, is imme-
diately extinguished, and a dog held for a short
time in the gas is thrown out apparently lifeless,
and would be entirely so were the experiment
carried on long enough."
"Does it not hurt the dog very much to be
used in this way ?" asked Mary.
SSee "The Surface of the Earth," p. 166.





SULPHUR


"Apparently not, for he soon recovers suffi-
ciently to pick up the bit of meat which is given
to him as a reward, and then runs away as lively
as ever. From this custom of showing to travellers
the effect of the gas on a dog, the cave has ob-
tained the name of Grotto de Cane.
As the fourth class of minerals is a small one
(so far as we shall speak of it), I will proceed to
that at once. It contains sulphur, which is found
abundantly in its native state, and also in combi-
nation with various metals."
And we know that it crystallizes," said Mary,
"because you melted some on purpose to show
it us."
"It crystallizes in acute octahedrons, and is also
found in masses. You all know its peculiar yellow
colour, the blue flame with which it burns, and
the suffocating smell it sends forth in burning.
This mineral is very common in the neighbourhood
of volcanos, whether active or extinct. Our own
supply comes chiefly from Sicily, where there are
extensive beds of sulphur on the south coast."
The children thought we could not want much
in this country, for they did not remember any
use for it except in making matches. They were
therefore astonished to hear that we import six-





46 FIRST STEPS IN GENERAL KNOWLEDGE.

teen or seventeen thousand tons from Sicily every
year, besides the large quantity we obtain during
the roasting of some ores of iron and copper.
"What can we possibly do with such a quantity
of sulphur ?" asked Robert.
"We use it for making gunpowder, for bleach-
ing, for the manufacture of sulphuric acid, and
for medicine. Also for taking impressions of
gems, &c., which is done by pouring melted sul-
phur into hot water; it then becomes like soft
wax, and can be conveniently used for the purpose,
growing hard as it cools."
Henry inquired about the manufacture of sul-
phuric acid, and was told that it is carried on upon
a very large scale, because this acid is of great
importance in various arts and manufactures.
It is found occasionally in a natural state in
the neighbourhood of volcanos," said his father,
"and so is likewise sulphurous acid gas."
Is not sulphuric acid a gas ?" asked Mary.
No: it is liquid, and is colourless, like water;
but it is of a soft and almost oily substance, which
has caused it to be commonly called oil of vitriol."
Robert thought oil of vitriol was of a brown
colour, but he was told that this is only after it
has been exposed to the air.








CONVERSATION V.

COMPOUNDS OF A SALINE NATURE.
FORMS Of CBYBTAL8- AMMONIA NITRATI 01 POTASH-SODA-
COMMON SALT-LIXI-MIAGNBIA-ALUMINA.
"BEFORE I proceed farther with the description of
mineral substances, tell me what are the forms of
crystals you have learned to make and understand."
"Only two, papa-the cube and the octahedron;
but you remember we made several other figures
when you taught us to cut one out of the other."
"These belong to what is called the first system
of crystallization, and now, with very little trouble,
you can get an idea of the second. Take your four-
sided stick, and cut another piece from it, longer
than it is broad. That is right; now cut another
much shorter than it is broad."
Henry did so; and he wished to
know what he was to call these pieces. -
For," said he, they cannot be cubes,
because their sides are not all equal."
"They are called right square prisms; the short
one as well as the long one is so called: and if you





48 FIRST STEPS IN GENERAL KNOWLEDGE.

were to take the long one, and cut from it an octa-
hedron (also longer than it is broad),
that would be a right square octahedron."
Robert thought prisms were three-
sided, like that which shows rainbow
colours, and he wished to know why
they are called right prisms.
"Right simply means upright, not sloping, and
as to the number of sides, a prism may have three
or more. However many sides a column may have,
it is still a prism. Among minerals the prisms are
either four-sided or six-sided."
Henry objected to the term "square" for pieces
which were more like oblong; but he was told that
the square prism has its base (the part it stands
upon) a square.
When we come to a mineral whose crystals
are described as right square prisms, you will not
be at a loss to understand their shape."
"Oh no," said Henry, "I shall be sure to recol-
lect these second shapes and the first too, because
I have been able to make them all from the same
piece of stick."
I am afraid these crystals are getting too diffi-
cult for me," said Mary.





CRYSTALS OF THE FIRST AND SECOND SYSTEMS 49

Do not despair," said her father; I will give
you several figures to copy, without requiring you
to remember the names. I wish you to get familiar
with forms rather than with names. It was neces-
sary that I should say thus much about these new
forms of crystals, because we now approach some
minerals in which they occur; but I shall not
trouble you with many difficulties of this sort."
Here her father gave out for the children's imi-
tation specimens of crystals of all the six systems,
with the names annexed.
CRYSTALS OF THE FIRST SYSTEM.




Cube. Oclahelron. Dodcaealdron.
CRYSTALS OF THE SECOND SYSTEM.

FYT"i


Right Square Prism.


Square Octahedron.






50 FIT STEPS IN GENERAL KNOWLEDGE.


CRYSTALS OF THE THIRD SYSTEM.


Reciangiiy r Prum. Rhombic Prism. Rhombic Octahedron.
CRYSTALS OF THE FOURTH SYSTEM.




\ \ \

Right Rhomboidal Prism. Oblique Rombic Prism.

CRYSTAL OF THE FIFTH SYSTEM.






Oblique Rhomboidal Prism.

CRYSTALS OF THE SIXTH SYSTEM.





Rhombohedros. Hezagonal Prim.





AMMONIA, OR HARTSHORN.


Let us then proceed to minerals of the fourth
class: and first, ammonia, which perhaps you
know by its common name of spirits of hartshorn.
This is found as a white crust in the neighbour-
hood of volcanos, and sometimes about the seams
of burning coal. It crystallizes in regular octa-
hedrons, but some of the salts of ammonia crys-
tallize in rhombic prisms."
Mary knew that ammonia is useful in medicine,
and also that hartshorn is used as a relief to head-
ache; but she was now told that it is also used in
manufactures, and that we do not depend for our
supply on what is obtained from volcanos, but
make sal-ammoniac from animal matter, or coal
soot, or from a liquor condensed from the gas-
works.
Another important mineral of this class," said
her father, "is nitrate of potash, which crystallizes
in similar prisms, and sometimes in needle-shaped
crystals on old walls and caverns. You know the
use of nitre, or saltpetre, Henry ?"
"Yes papa, it helps to make gunpowder and
other fulminating powders."
It is also much used in the manufacture of
nitric and sulphuric acids, and is therefore pro-





52 FIRST STEPS IN GENERAL KNOWLEDGE.

cured in large quantities both naturally and by
artificial means. Another valuable member of this
group is soda, which, whether as carbonate of
soda, as Glauber salts, or in its other forms, is
highly useful. The crystallization of Glauber salt
is in oblique rhombic prisms. But all these must
yield to common salt in value, and this is very
simple in its modes of crystallization, which are
the cube and its secondaries."
"What do you mean by its secondaries ?" asked
Robert.
I mean the forms derived from it, such as you
made by cutting off the corners of a cube. Salt
also crystallizes on some occasions in
S" shallow cups, but these are square at
the surface of the brine in which they
are formed, and pointed at the lower end, forming,
in fact, half an octahedron."
Mary asked if they might see the crystals of
salt, so Robert was desired to fetch a tea-spoonful
of salt and a wine-glass of water, and his father
having thoroughly dissolved the salt, took up a
drop of the water on the end of a glass rod, and
laid it on the warm mantelpiece, where it slowly
evaporated, and where the children were delighted





SALT MINES.


to find a number of tiny cubes of salt more or
less perfect in their forms.
If the water is quickly evaporated," said their
father, the salt forms a granular mass, without
regular forms. Salt is largely obtained in hot
countries by the evaporation of sea-water; but the
finest salt is rock-salt, which occurs in masses in
the earth, and, like other minerals, is dug out and
brought to the surface by miners."
Oh! I remember," said Mary, that I have
read about some salt-mines abroad, where there is
a curious chapel of salt underground."
Those mines are near Cracow, in Poland, and
are about eight hundred feet deep: but they are
worked at three several depths, and it is in the
upper story, only two hundred feet below the sur-
face, that the chapel is formed."
Is it a real chapel," asked Robert, "and do
people worship God in it?"
It is a real chapel, thirty feet long, twenty-
four feet broad, and eighteen feet high, entirely
sculptured out of the salt rock. as are its pulpit,
its altar, and the twisted columns that support its
roof. It is certainly intended for the worship of
God, but the statues of the Virgin Mary and of





54 FIRST STEPS IN GENERAL KNOWLEDGE.

St. Anthony (which are also hewn in salt) are set
up in it, and invite a portion of that homage which
is due to God alone. There are other chapels in
the same mine, and likewise tool-houses and stables,
all cut out of the salt rock; and there are even
small and delicate sculptures in the same material
offered for sale on the spot, but these are not, as
you may suppose, very lasting, as salt is so easily
affected by moisture."
Oh, yes," said Mary, in damp weather I have
seen it being dried in the oven, and then rolled
and sifted before it is put into the salt-cellars.
How very useful salt is!" she added; I do not
know what we should do without it."
Without salt," said her father, we could not
long exist; and if we were limited to a small
supply, we should soon fall into a state of disease.
Salt is the great preservative from corruption, and
therefore, in mercy to mankind, God has furnished
us with an inexhaustible store of this precious
material."
Yes," said Henry, there are salt mines, and
salt springs, and salt lakes; and, if these were all
exhausted, there is the great ocean itself, with
plenty of salt always in it."





VARIETIES OF LIME-GYPSUM.


Mary asked if salt is used by savages as well as
by civilized people, and she was told that it is, and
that if she were sailing among the isles of the
Pacific, she would see a rude contrivance for eva-
porating sea-water, the invention of the ignorant
islanders, and corresponding with our own simplest
method.
Passing by Borax, which is another of the
salts of soda, and merely mentioning that the
two next minerals, Baryta and Strontia, are of
comparatively little importance, but that the one
gives the green and the other the red light to fire-
works, we come next to Lime, a most useful and
important substance, which we are familiar with in
a variety of forms. You remember, Henry, the
large heap of gypsum we saw the other day near
the mill, and which was to be ground up and used
as manure."
Oh yes, papa; and you told me that what we
call Plaster of Paris is nothing but this gypsum
burnt and ground."
Gypsum is a sulphate of lime, and occurs in
several forms, so that it may not only be in large
masses as you saw it, but in plates, or in starry
forms, or in clear bright crystals, like glass."





56 FIRST STEPS IN GENERAL KNOWLEDGE.

And what shape are the crystals?" asked Mary.
"They are of the shape which you said was
simple to look at, though it has a difficult name-
I mean the right rhomboidal prism."
Mary showed one which she had cut out of a
piece of bread, and her father said that in sulphate
of lime the crystals usually have bevelled sides,
and sometimes they occur in what are
called twin, or arrow-head crystals, where
two of these prisms are joined together.
He also showed the children a fine-
grained and beautiful piece of alabaster,
being a different form of gypsum.
The great importance of carbonate of lime was
then spoken of, which,
under the different names
of Iceland Spar, Stalac-
tite, Chalk, Limestone,
&c. is well known, and
in any of its forms, when
burnt, becomes quick-
lime. A very pretty spe-
cimen of a white and
fibrous substance, called
sA,, ,,PA. satin-spar, was also shown





CARBONATE OF LIME-MARBLE.


as another form of carbonate of lime, hard enough
to be made into snuff-boxes, and turned into studs.
Lime is brittle, white, and powdery," said
Henry, "and not much like stalactite, which is
very often a beautiful transparent thing like an
icicle. Then chalk, again, is so soft that we can
write with it, while spar is so hard that it will
scratch things."
Very different from either is marble; but this
is a species of limestone, the coarser varieties being
the common white and clouded marble, and the
finer the statuary marble, or that which is used
for statues."
Then this is carbonate of lime," said Henry,
touching the chimneypiece. Could we make it
into quick-lime by burning it ? and could we make
it froth up by pouring powerful acids upon it ?"
Pray do not try," said Mary, for you may
think how vexed mamma would be if you were to
spoil this beautiful marble."
I can give you some fragments of marble to
try experiments with," said his father; and
when you come to use the blow-pipe, you will
find that marble is subject to the same laws as the
other varieties of carbonate of lime, the carbonic
acid being driven off, and the lime left in a pure





58 FIRST STEPS IN GENERAL KNOWLEDGE.

state. Sometimes, however, limestones contain a
portion of clay, and in such cases the residue is not
pure; it then forms a sort of lime from which a
cement can be made that sets under water."
It is always useful, then, which ever way it is
found."
Very useful; and that not only as mortar and
cement, but for improving lands, for clarifying
sugar, for purifying gas, for clearing off the hair
from hides in tan-yards."
And for making white-wash, papa," said
Robert, who remembered a general whitening and
cleansing of the cottages in their parish during the
last summer.
Yes, Robert, and no unimportant use either;
for I believe the health of our cottagers very much
depends on the purifying effects of lime as a frequent
white-wash for the interior of their dwellings."
Mary said she thought rich people as well as
poor used lime to purify their rooms; for, one
day, when mamma called on a lady she had not
seen for a long time, she found two of her children
very ill; and the lady, fearing it might be a fever,
had ordered several dishes of lime-water, or some-
thing of the sort, to be placed in different parts of
the house."





CARBONATE OF LIME.


That was chloride of lime," said her father,
" a valuable purifier indeed, and one that is not
sufficiently resorted to when any unwholesome
influence is present."









CORAL-FORKMD CARlBOATI OF LIMN.
The children were then shown a beautiful speci-
men of carbonate of lime, resembling coral, which
is not uncommon in the Cornish mines. Although
it is a mere collection of chalky matter, covering
some small substance which serves as a nucleus, yet
it often deceives the eye from its likeness to a
branch of coral. They were also shown .
the fundamental form of crystal, ".
which is a rhombohedron. But they
were told that the crystals vary greatly, HOMBORnDAON.
and that carbonate of lime is sometimes found of a





60 FIRST STEPS IN GENERAL KNOWLEDGE.

fibrous texture, and with a lustre like satin, as in
satin spar; or it may be white and earthy, like
chalk, but so much softer as to be called rock-
milk; or it may be a collection of small round
grains compacted together into a limestone, which
bears the name of oolite; or it may be in a mass
of silvery plates, which has the name of argen-
tine.
There are other salts of lime which I need not
particularise," said their father, but I must just
mention fluor spar, (fluate of lime,) or, as we call it,











FLUOR SPAR.
Derbyshire spar, which crystallizes in cubes and
octahedrons, and is a beautiful substance for orna-
mental purposes, very abundant in the county from





MAGNESIA.


which it is named, and manufactured there into vases,
and other ornaments. From it is obtained fluoric
acid, which is employed in etching on glass. With
this I leave the subject of lime, and turn to a mineral
of which I have two specimens in my medicine
chest; here is one of them."
The children well knew the medicine which their
father showed them, for it was carbonate of magne-
sia; but they were much surprised when he took up
the second specimen, and they saw it was Epsom
salts.
Magnesia and salts are not the least alike,"
said Mary, and they do not taste alike."
Yet one is the carbonate and the other the
sulphate of magnesia. You notice a great dif-
ference in them now; is there also a difference
when we mix them with water ?"
Oh yes, a very great difference," said Robert;
" magnesia makes the water look milky, and
mamma is obliged to keep on stirring it to the
last minute, or else it sinks to the bottom before
we can take it; but salts cannot be seen at
all after it has been mixed, and we should not
know it was there, except for the nasty bitter
taste."





62 FIRST STEPS IN GENERAL KNOWLEDGE.

All those salts of magnesia which are capable
of being dissolved in water, have a very bitter
taste, like Epsom salts; all those which cannot be
dissolved, have merely an earthy taste. The sul-
phates and the nitrate of magnesia can be dissolved,
the carbonates and other salts cannot."
And where does magnesia come from ?" asked
Mary.
It is found among limestone rocks, traversing
them in fibrous white seams. The floors and roofs
of limestone caves are sometimes covered with
minute crystals of the sulphate of magnesia (Epsom
salts); or it occurs dissolved in the water of mine-
ral springs. This is the case at Epsom, in Surrey,
whence the common name. But Epsom salts can
be very easily manufactured; and this is largely
done, to meet the demand for this useful medicine.
Our next mineral," continued her father, "is
alumina, of which we have already noticed the
common alum. This exists in certain rocks, called
aluminous slates, or shales, and these are quarried,
subjected to heat, and afterwards washed until
they yield their alum. One of the salts of alumina
is the pretty blue turquois, which takes so good a
polish, and ranks among gems. A mountainous





MINERALS OF TE FIFTH CLA CONCLUDED. 63

district in Persia is famous for the abundance of
its turquois, which is so much esteemed, that the
Persian monarch is said to keep all the large and
finely-coloured specimens for his own use.
With this pretty example, I conclude my
description of minerals of the fifth class. Can you
now tell me what minerals compose the four pre-
ceding classes ?"
The children were obliged to think for some
time before they could answer; but, at last, one
helping the other, they recollected that the first
class contains gases, the second water, the third
carbon and compounds of carbon, and the fourth
sulphur.
I do not know what to say the fifth class con-
tains," said Henry, there are so many useful
things in it; but, of course, I shall always recol-
lect common salt being in it."
That will be a help to you," said his father,
and may serve to fix in your mind that minerals
of this class are chiefly compounds ofa saline nature.
This will answer my purpose as well, in speaking
to you of the fifth class, as if I were to use the
difficult word by which these minerals are described
in books."










CONVERSATION VI.

EARTHY MINERALS.
PURE SILICA, OR QUARTZ-VITREOUS VARIETIES-ROCK CRYSTAL-
AMETHYST-TRANSLUCENT VARIETIES-FLINT-AGATE-CORNELIAN
--OqYX-SARDONYX-BREAST-PLATE OF AARON.

WHEN the snow was off the ground, and a few
of the hardy February flowers began to peep out
of the soil, the children were soon busy with spade
and rake, setting to rights their own gardens.
Their mamma, while watching their labours, ad-
vised Robert to get a weeding basket, and pick off
all the stones he could find; for after all their
rakings, there were still many pebbles left on the
surface. Robert fell busily to work, and soon
collected a great many. He asked where he should
put them; and his mamma told him to carry them
into the hall, and perhaps his father would give
him a lesson about them.
That will be droll," said Robert, to learn a
lesson from the stones out of my own garden."
You would be a clever child," said his mother,





QUARTZ-ROCK-CRYSTAL.


" if you had learned all the lessons to be gained
from even your own little plot of ground."
Henry looked into the basket, and said they
were all common stones and pebbles, with not one
that was pretty looking amongst them; but he
went in with his brother and sister to hear what
papa would say about them.
These," said his father, with most other
common pebbles of the soil, and of gravel beds,
are simply portions of a mineral sub-
stance called quartz, or pure silica; a
most abundant substance in nature,
and taking a variety of forms. It is
very hard; it will not melt under the
flame of the blow-pipe; it is not acted
upon by the powerful acids which are Q
used as tests of minerals; and it will c"rTA",.
not cleave asunder in any regular manner."
What a stubborn mineral!" exclaimed Mary.
"The purest form of quartz," continued her
father, is rock-crystal, used in jewelry, and also
for optical instruments and spectacle glasses. A
bluish-violet quartz crystal is much esteemed as a
gem, and well known to you as amethyst. The
name of this stone is derived from a notion among
F





66 pFls STEPS IN GENERAL KNOWLEDGE.

the ancients that it possessed the power of prevent-
ing intoxication; so that any one might drink to
excess, without harm, from a cup made of ame-
thyst. Of course, this was a mere delusion, and
must have been frequently disproved; but what
people wish to believe, they easily persuade them-
selves to be true."
Amethyst is of a beautiful violet colour by
daylight," said Mary, but by candle-light it looks
brown, which is a great pity, because ornaments
are most worn in the evening."
This stone," said her father, was, until
lately, always set in gold; but recently, a setting
of frosted silver has been adopted, with elegant
effect. You will like to know whence we get our
finest amethysts, namely, from Ceylon, the Brazils,
and the kingdom of Murcia, in Spain. Other
valued specimens of quartz are known under the
names of rose quartz, smoky quartz, milky quartz,
false topaz, &c., and are also used for ornamental
purposes. All these belong to the vitreous or
glassy varieties of quartz."
I did not expect to hear of transparent stones
of quartz being related to these dull looking things!"
said Robert.





FLINT-COMMON AND VARIEOATD.


Besides these, there are others that are not
transparent, but yet admit of light passing through
them. What is the word for that, Henry?"
Translucent, papa."
Of these varieties there is one that is, indeed,
very feebly translucent, but which is exceedingly
common and useful-I mean the flint, or compact
silica, which abounds in our chalk hills, and which
is broken up as the material of our roads. Vari-
egated flint pebbles are sometimes met with having
curious marks resembling figures of animals. A
flint was once found near Norwich on which a










CURIOUS VARIGOATZD FLINT.
tiger's and a boar's head seemed to be represented.
But some of the more perfectly translucent varieties





68 FIRST BTEP IN GENERAL KNOWLEDGE

of quartz are very beautiful, as you are your-
selves judges; for you know the appearance of
agate and cornelian."
Oh, yes!" said Mary, mamma has some
agates, which she allows me to play with; may I
fetch them now, that you may tell us the names of
the stones ?"
You may fetch them," said her father, but
I am not sure that I remember the fanciful names
given to the various agates."
Mamma has told me the name of this one,"
said Mary, as she returned, and held up an agate,
having many angular lines marked upon it. It
is called fortification agate, because these zigzag
lines are very much like the plan of a frtified place.
Here is another," she added, "where the lines are
beautifully regular, and close together; but they
are straight instead of zigzag; what is that called ?"
That is the ribbon or banded agate; and it is
by cutting through a number of slender cylinders
that this appearance is given. A slice cut from
the top of this kind of agate, instead of through
the whole length, would show the ends of all the
cylinders, and would then be called eyed agate,
from its resemblance to a number of eyes. This





CHALCEDONY, OR AGATB.


agate with moss-like markings, is called moss-agate;
and here is a stone without any markings, and of
a rich red tint-this is called cornelian."
Are cornelian and agate, then, the same kind
of stone, one being plain, and the other variegated ?"
asked Henry.
"They are," said his father; "for both are
specimens of Chalcedony, so named from Chalcedon,
a city of Bithynia, in Asia Minor, where this stone













CHALCEDOYT, OR AGATI.
was abundant. In itself, it is colourless, or of a
pale greyish, or bluish tint; but in its different
variations, it has many well-known names. When





70 FIRST STEPS IN GENERAL KNOWLEDGE.

of a deep brownish red, it is called sard; when
the colours occur in distinct layers, it is onyx;
when these layers consist of sard and white chalce-
dony, alternately, it is called sardonyx; when the
whole stone is greenish grey, translucent, and with
internal reflections, it is called cat's-eye."
Henry thought he had found such a stone among
the agates, but the green colour was sprinkled with
yellow and whitish dots; and he was told that
chalcedony so marked, is called plasma.
Mary said she had seen a beautiful brooch, on
which a white figure was engraved, and raised
upon a brownish ground; and she thought the
figure had been made separately, and fastened on,
until her mamma told her to the contrary, and
explained how the whole of the brown stone had
been at first covered with a white layer, and how
the workman had cut away that layer, except just
at the place where the white figure was to be
engraved. But," she said, I am sure mamma
did not call it an onyx, or a sardonyx, or an agate;
it was some other name."
I dare say she called it a cameo, which is the
name given to these engraved stones. The ancient
Greeks and Romans possessed the art of engraving





ENGRAVED GEMS-TKE ONYX.


on gems, and were so skilful, that the specimens
of their work still existing, are valued at enormous
prices, and will probably never be excelled in
beauty. I have seen an engraved onyx in the
cabinet of Dresden, which is valued at 44,000
dollars."
Robert asked the value of a dollar, and was told
that in Germany it is three shillings.
Mary remembered reading about the onyx in
the Bible, and she asked Henry to help her to find
out the passages where it is named. They found
it mentioned in Gen. ii. 11, 12, as the production
of the land of Havilah; in Exod. xxv. 7, among
the gifts which the children of Israel were com-
manded to bring for the use of the tabernacle; and
in Exod. xxviii. they found an interesting account
of its use in the tabernacle service, which their
father told Mary to read aloud; first asking her if
she remembered what her mother had said the
Sunday before about that part of the High Priest's
dress, called the ephod.
Mamma called it a vest of rich brocade," said
Mary; and she told me, that upon the front part
of each shoulder-strap there was a precious stone;
and besides this, there was a breastplate of pre-





72 FIRST 6TEP8 IN GENERAL KNOWLEDGE.

cious stones fastened to the shoulder-straps and
girdle with gold chains."
Now read the passage," said her father, and
you will see what was engraved upon these stones."
Mary read thus. And thou shalt take two
onyx-stones, and grave on them the names of the
children of Israel:
Six of their names on one stone, and the other
six names of the rest on the other stone, according
to their birth.
With the work of an engraver in stone, like
the engravings of a signet, shalt thou engrave the
two stones with the names of the children of Israel:
thou shalt make them to be set in ouches of gold.
And thou shalt put the two stones upon the
shoulders of the ephod for stones of memorial unto
the children of Israel: and Aaron shall bear their
names before the Lord upon his two shoulders for
a memorial."
When Mary had read this, her father remarked,
that as to whether the onyx-stones here mentioned
were like what we now call onyx, we cannot be
certain. Robert asked if there was any engraving
on the precious stones of the breastplate ?
Yes," said Henry; here is an account of it





oGzM IN THa HIGH PRIEST'S BRBASTPLATE. 73

in the same chapter: there were twelve stones in
the breastplate, and each stone had the name of
one of the twelve tribes upon it, so that Aaron
might bear all their names on his heart before
God."
Then the names were engraven twice over,"
said Robert, and the High Priest carried them on
his shoulders and on his breast. I should like to
know what the twelve stones of the breastplate
were ?"
I can tell you," said Henry, for here they
are put down in the seventeenth and following
verses.
And thou shalt set in it settings of stones,
even four rows of stones: the first row shall be a
sardius, a topaz, and a carbuncle: this shall be the
first row.
And the second row shall be an emerald, a
sapphire, and a diamond.
'And the third row a ligure, an agate, and an
amethyst.
And the fourth row a beryl, and an onyx,
and a jasper: they shall be set in gold in their
enclosings.'"
I do not know all these stones," said Robert;





74 FIRST STEPS IN GENERAL KNOWLEDGE.

" and if I did, I should not know why the High
Priest had to wear them, with the names of Joseph
and his brethren upon them, when he was doing
service in the tabernacle."
Have I not explained to you," said his father,
"that the High Priest of the Old Testament dis-
pensation, whose office it was continually to offer
sacrifices for sins, was a type of the Saviour, our
great High Priest, who offered himself' without
spot to God,' as a full, perfect, and sufficient sacri-
fice for the sins of the whole world ?"
Yes, papa, you have often told us that."
Then, remember also, that as the High Priest
of old bore the names of his people on his heart
when he went into the tabernacle of God, so does
our compassionate Saviour bear the names of his
people on his heart before the throne of God,
'where He ever liveth to make intercession
for us.'"








CONVERSATION VII.
EARTHY MINERALS (continued).
QUARTZ COIWTI UED JASPER- BLOOD-BTON LOAT-STONZ-PTRBI-
FIND WOOD-OPAL-0OAP-BTON--POTI-TONI-TAL--BPNUTINE
-XMBBRCHAUM.
THE children were wondering at the great variety
there is in quartz, when their father told them he
had not done with this mineral, but had yet to
speak of the varieties more or less resembling
jasper.
I suppose jasper is very beautiful," said Mary,
"for we always read of it in stories where a palace
is described?"
Jasper is indeed a handsome stone, and admits
of a high polish; but it does not rank among gems.
It is a dull red or yellow flinty rock, though some-
times found of other colours, or nearly colourless.
It may be obtained in large pieces, and on this
account, as well as its mirror-like brightness, it is
fit for the palaces of kings, where it is usually
employed for inlaid work. There are almost as
many varieties in its appearance as in the agates,
but instead of being translucent, it is almost





76 naTr m i nr GoaElAL KOWLIGO.
wholly opaque. Some jaspers, however, present
a mixture of jasper and agate, and according as
the one or the other is most conspicuous, the spe-
cimen is called a jasper-agate, or an agate-jasper.
One of the jaspers is the well-known blood.
stone, or heliotrope, and there is likewise an agate
so called."
That is a green stone," said Henry, with
blood-red spots."
It is; and in the early ages of Christianity
these stones were much employed in the engraving
of sacred subjects. In the royal collection at
Paris, there is a bust of the Saviour cut in blood-
stone, the spots being so managed as to represent
the drops of blood on His sacred brows."
Mary wished very much that she could see that
famous stone; but her father told her that she
would be disappointed in it, as she would in any
attempt to represent the passion of the Saviour.
" No human mind," he said, can comprehend
the depths of that suffering, therefore no human
hand can worthily portray it. Least of all should
the attempt have been made with a green stone,
which of course renders the face ghastly and
unnatural."





CURIOUs JASPER IN THE BRITISH MUSEUM. 77

Are there any more curious jaspers?" asked
Robert.
Here is an accurate
copy of a specimen of
jasper in the British
Museum, which in its
two fractural surfaces
presents a natural and
striking likeness of the
poet Chaucer. There
are also several others
that we may call curious
from the forms we find
them in, such as Float- Co. ,m.
stone, which is a bundle of fibres or filaments of
quartz collected together in a sponge-like mass,
and so light as to float on water. This is found in
the chalk formations near Paris. Petrified wood
may also consist of quartz, and sometimes these
petrifactions are of chalcedony or agate, which
are sawn across and polished, showing in a very
beautiful manner the natural grain of the wood. A
singular fact connected with quartz crystals is, that
they sometimes enclose small portions of other mine-
rals, or they contain cavities filled with some fluid."





78 FIBST STEPS IN OGENRAL KNOWLEDO.

What is the shape of the crystals?"
The crystallized varieties of quartz usually
occur in six-sided prisms, more or less perfect, and
ending in six-sided pyramids. But I am now
about to lead you from quartz to opal, a stone
which, in its finest varieties, presents a remarkable
play of colour reflected from the interior, and
often of the most delicate tints of red, yellow,
green, &c."
It must be almost as beautiful as the diamond,"
remarked Mary.
The finest Turkish opals, of the noble or pre-
cious kind, are as valuable as diamonds. These
stones are also found rather abundantly at Kaschan,
in Hungary, but the specimens are very small, and
it is only after working many years that an opal
of tolerable size is discovered. Some years ago, a
very fine specimen was met with at that place, of
the size of half-a-crown, and the price demanded
for it was something more than three thousand
pounds."
I am sure I have read something about the
precious opal in Roman History," said Henry.
Was not that the stone which Mark Antony
wished to take away from one of the senators, and





BEAUTY OF THE OPAL.


the man was so fond of it, that he chose rather to
go into exile than to give it up ?"
It was; and we need not wonder that the
senator (Nonius was his name) should choose exile
rather than part with such a treasure, for, according
to some authorities, the value of his beloved opal
was one hundred and sixty thousand pounds!"
It must have been a splendid stone, to be
worth so much money! said Mary.
No doubt it exhibited in great brilliancy those
flashes or flames of colour which are so remarkable
in the opal, when it is turned about in the hand.
The great esteem in which the ancients held the
opal may be gathered from a name they gave it,
which signifies Child beautiful as Love.' "
What is there in the stone to cause that
appearance of flashes ?" asked Henry.
There are a number of very minute fissures or
cracks, filled with thin films of air, and it is these
which refract the light, and produce the beautiful
colours."
Then the opal is beautiful because it is full
of cracks," said Mary. That is very odd, for if
any other stone was cracked, we should think it a
great fault."





80 FIRST STEPS IN GENERAL KNOWLEDGE.

That is true," said her father; and it is so
far a fault in the opal, that it renders it very
fragile, and liable to split open by a sudden change
of temperature. Besides this precious opal, there
are other varieties far less beautiful, and therefore
less esteemed. They all rank as common opals,
and rarely reflect more than one colour in the
same stone. The opals can be easily scratched by
quartz, and this is how they are distinguished from
some silicious stones often called opal. Opals are
infusible before the
blowpipe, and have
no appearance of
crystalline structure.
Near to them come
several minerals hav-
ing a slight feeling of
greasiness, and one
of them on this ac-
AP-S^TONZ. count is called soap-
stone."
I have seen it," said Henry, and it looks
something like mottled-soap. It will take out
grease-spots from one's clothes, and the tailor uses
it instead of chalk to draw lines on the cloth when





TALC--OAP4-TOXE- OT-STOUL


he is cutting out a coat; and mamma told me that
in some places it is used as we use soap."
More strange than this," said his father, the
negro tribes at the mouth of the river Senegal eat
this substance with their rice."
It must be a softer kind of soap-stone than
I have seen," remarked Henry, "or else they must
grind it to powder."
It is soft and of a waxy white, like Windsor
soap, and the eating of it does not appear to
give them any inconvenience. But soap-stone,
or (as you will often find it called) steatite, when
exposed to a great heat, becomes so hard as to
take a very fine polish. It is therefore useful in
making porcelain. But it is not always white;
for it is sometimes striped with various ochres,
and when hardened it is frequently of a dark
green colour. You have seen that thin translucent
leafy substance called talc. Now, soap-stone is an
impure kind of talc, and so is pot-stone, a sub-
stance which is soft enough, when first brought
from the quarry, to be turned in the lathe, and
converted into various utensils, but afterwards
becomes quite hard, and being infusible, is of great
use for purposes where heat is required. Lamps





82 FIRST STEPS IN GENERAL KNOWLEDGE.

are made of pot-stone in Greenland, ovens and
stoves are lined with it in Norway, and it is em-
ployed for cooking
utensils in Lombardy.
Here is also a drawing
S of three English speci-
mens of Hone-stone,
Se muchvalued bycutlers,
though our best hone-
stones are imported
from Turkey. Among
these stones having an
unctuous or oily feel-
ing, I must not forget
to name to you the
precious and the com-
mon serpentine, both
of which possess this
quality in a slight de-
gree."
Have they anything to do with serpents, or
are they twisted about, that they are called ser-
pentine ?" asked Robert.
"I think it must be owing to the rich green
colour of the stone, and the spots and stripes that





MEBRCHAUM.


sometimes mark it, reminding one of the chequered
skin of the serpent. The precious variety is
translucent, and sometimes has garnets imbedded
in it; the common is opaque. Both may be easily
cut with a knife."
These soft stones seem almost like earth or
clay," said Mary.
Some of them very nearly resemble clay,"
said her father; "especially a substance called
meerschaum, or sea froth, but which is really
composed of magnesia, carbonic acid, and a little
silica. This substance is common in Greece and
Asia Minor, and when first dug up is quite soft,
and will lather like soap. It is used by the
Tartars for washing linen, but its most important
use is for making the bowls of pipes. For this
purpose there are various processes employed to
give the meerschaum the necessary colour, con-
sistence, and polish; such as boiling in milk, or
softening in tallow, and in wax. At last it
becomes the smooth, hard and beautiful substance
employed in German pipes."










CONVERSATION VIII.

EARTHY MINERALS.
ASBETUSB-AMIANTHUB-HORNBLENDE-SAPPHIRE-RUBY-FELSPAR
-PORCELAIN CLAY-MOONSTONE -SUNSTONE ALBITE LABRA-
DORITE POTTER'S CLAY GARNET TOURMALINE MICA-
TOPAZ LAPIS-LAZULI AND EMERALD.
THE children came to their father one morning
in much astonishment, to tell him of a conjuring
trick described by one of their young companions,
by which a person might hold red-hot iron in his
hand, or expose his arm to the flame of a candle,
and still remain unhurt.
Certainly, if he wear a glove or a sleeve made
of asbestus," replied their father.
What is asbestus?" asked Robert.
It is a mineral substance, in which the crystals
are in the form of long, slender fibres, placed side
by side. Several varieties of hornblende are of
this description, and receive various names accord-
ing to the degree of regularity of the crystals.
The most beautiful asbestus is a flax-like variety,
called amianthus, which can be woven into cloth."





A8BESTUS.


Mary was much amused to hear of mineral
cloth, and much astonished when she learnt that
this cloth is incombustible, and
may be thrown into the flames
without injury.
"A single fibre, indeed," said
her father, "may be easily fused;
but in the mass it will resist ordi-
nary flame."
How can they weave mineral
fibres," asked Henry, "without con-
tinually snapping them in pieces ?"
At first they interweave fibres
of flax with those of asbestus, and
then passing the cloth through a
furnace, the flax is consumed, and
the fire-proof material remains.
A glove made of this cloth will
enable the wearer to hold red-hot
iron for several minutes without
inconvenience."
I should like an asbestos frock,
which would never take fire," said """"
Mary; only I suppose it would be very stiff
and ugly."





86 rm arnar nr ea.nua, mKowIo .
"That would depend upon the fineness of the
fibre, and of the weaving. Italian ladies have
succeeded in getting it fine enough for lace, and
in Napoleon's time, the wife of the Viceroy of
Italy possessed a veil of amianthus. Girdles are
sometimes manufactured of this substance, inter-
mingled with silver thread. The word asbestus
means indesthr ible, while amianthus signifies tn-
stained. This latter name alludes to the fact that
the material passes through the fire not only
without injury, but that it is in that way purified
from any spot or stain which it may have acquired."
Mary again expressed a wish for a frock of this
material, adding, How droll it would be to put
my frock in the fire when it was dirty, instead of
having it washed."
Her father said that a story was told of Charle-
magne, that he had a table-cloth of amianthus
which he would sometimes throw into the fire after
dinner, that he might enjoy the astonishment of
his guests.
"Fire-proof cloth has not then been lately
found out ?" said Henry.
"By no means. It was employed by the an-
cients to enclose the remains of persons of dis-





ABBBSTUS CLOTH.


tinction on the funeral pile. There now exists in
the Vatican at Rome, an asbestus shroud, contain-
ing ashes and burnt bones several thousand years
old."
"But how could they be burnt if they were
well wrapped up in fire-proof cloth?" asked Mary.
It is so far fire-proof, that it is not consumed
in the fire, but after a time it comes to a red heat,
and then, of course, whatever is enclosed in it
must be destroyed. The object of an asbestus
shroud was not to keep the body from being con-
sumed, but to preserve the ashes of the deceased
from being mixed and lost among the embers of
the funeral pile."
The children were expressing their wonder at
the extraordinary nature of asbestus, when their
father remarked, that there is, after all, nothing
remarkable in a mineral substance being incom-
bustible, the really remarkable part being its
occurrence in fibres of sufficient length and fine-
ness to allow of its being woven. As to the
places in which it is found," he said, they are
numerous in the Hartz and the Ural mountains,
in Switzerland, England, Scotland, in the United
States of America, &c. It exists in serpentine





88 FIRST STEPS IN GENERAL KNOWLEDGE.

and various other rocks, and forms veins in which
the filaments are perpendicular to the surfaces of
the vein, and vary in length, therefore, with
its thickness. Hornblende, of which asbestus
is one of the varieties, is an essential part
of certain rocks called syenite, trap, and
hornblende slate, and this is the form of its
crystals. There is a common mineral called
pyroxene, the fibrous varieties of which also
bear the name of asbestus. The chief constituents
of these minerals are silica and magnesia. Near to
them come those in which silica and alumina pre-
vail; but the first I shall mention is a precious gem
consisting of alumina uncombined."
I am very glad you have not done with the
gems yet," said Mary.
"My present subject is the sapphire, whose
'celestial blue' is often spoken of. But perhaps you
are not aware that the sapphire may be of almost
any other colour besides blue, and that when the
term 'Oriental' is prefixed to the words ruby,
topaz, emerald, amethyst, &c., the stones thus
named are all sapphires, resembling in colour
the ruby, topaz, &c."
"I had not the least idea of it," said Mary;





ALUMNDA-THE SAPPHIBE.


" but thought the sapphire was always of the most
beautiful blue colour."
That is, indeed, the true sapphire colour, and
the name is still properly confined to gems of that
tint. The oriental ruby, or red sapphire, is, how-
ever, more highly esteemed; and when perfect in
colour, and free from blemish, is as costly as the
diamond. The King of Arracan is said to pos-
sess two magnificent oriental rubies, as long as the
little finger, and about an inch in diameter. This
is an extraordinary size, for they very seldom
exceed half an inch in their dimensions. The best
come from Pegu. The oriental topaz or yellow
sapphire, is of a pure yellow, varying in intensity;
it comes chiefly from Ceylon. A beautiful effect
is visible in some sapphires when polished on the
surface; a star of six rays, corresponding with
the six-sided form of the prism, is to be seen
within the crystal. In a blue sapphire, it is a star
of silvery brightness; in a red sapphire, it is a
gold-coloured star. These are the true Asteria
sapphire, and are curious and beautiful objects.
The blue kind is from Ceylon."
"What elegant and beautiful stones they must
be," exclaimed Mary.





90 FIRST STEPS IN GENERAL KNOWLEDGE.

The sapphire family are not all equally ele-
gant," said her father; for included in it we find
a much coarser substance, with dull and dingy
crystals, called corundum, and a granular variety
found in blackish masses, and called emery."
Surely not the same kind as that in my emery
cushion," said Mary; "for that is a powder, and
seems of no use, except to take the rust off
needles."
In its natural state emery occurs in large lumps
or blocks; but these are reduced to powder in a
stamping-mill, and afterwards ground finer in mills
of steel. This powder is not only convenient to
remove rust from your needles, but is highly useful
in the arts for heightening the polish of precious
stones, for giving brilliancy to metals, and an even
surface to mirrors. From this you will know at
once that it must be very hard; and, indeed, the
various kinds of sapphire come next to the
diamond in hardness. As I have described the
oriental ruby or red sapphire, so I must now pro-
ceed to mention the spinel or ruby, properly so
called. The spinel is known of various colours, but
is chiefly celebrated when of a vivid red. The term
spinel ruby applies only to stones of that colour."





FELSPAB.


I know what a bright and splendid red the
true ruby colour is," said Henry, for I have seen
it in old stained glass windows."
"' When the red is less bright, and inclines more
to rose colour, the stone is called Ballas Ruby.
This was formerly brought from the mines of
Balachan, in Tartary. The spinel ruby is much
valued, when of tolerable size ; but the crystals are
usually small, and the stone being inferior in hard-
ness to sapphire, is accordingly less esteemed.
Ruby occurs in granular limestone, also in gneiss
and volcanic rocks. It consists of alumina and
magnesia, with a little silica and peroxide of iron.
A number of minerals into which silica more
largely enters, follow the ruby; but they are so
little known, and their names would be so formi-
dable to you, that I must pass them by, and pro-
ceed to a natural group of minerals called the
Felspar family."
I hope they are an agreeable family," said
Mary, and beautiful to look at."
They are not strikingly beautiful," said her
father, but they are very useful; and that will
always make them interesting and important. Fel-
spar helps to compose various rocks, such as
granite, gneiss, porphyry, and basalt. It is also





92 FIRST STEPS IN GENERAL KNOWLEDGE.

extensively used in the manufacture of por-
celain."
How can a piece of rock be used in making
china ?" asked Robert.
It is when decomposed by natural causes that
felspar becomes a fit material for this purpose.
Extensive beds of a whitish chalky substance,
called kaolin, or porcelain clay, which is the de-
composed felspar, occur in granite regions, and
are quarried for the purpose. This substance goes
through various washings, kneadings, and admix-
tures with other materials, and at length is formed
into vases, &c., and baked, preparatory to the
enamelling, painting, and gilding which complete
the porcelain. And even this enamel is obtained
from common felspar, ground to a fine powder,
distributed over the objects, and melted in the
furnace to a white glaze. Besides common felspar,
there is a kind called Adularia, which is not with-
out beauty, certain varieties of it being set in
jewellery, under the names of Moon-stone and
Sun-stone. The former has peculiar pearly reflec-
tions, the latter a glittering effect, owing to the
presence of minute scales of golden yellow mica."
Are these all the members of the felspar family
you have to tell us of?" asked Henry.





PORCELAIN CLAY-POTTBBY.


There are about a dozen more," said his father,
" but I shall only mention two: Albite, a con-
stituent of many rocks, so named from its uniform
whiteness; and Labradorite, a gray or brown mine-
ral, lighted up by internal reflections of rich and
delicate colours. This is also a constituent of
some granite rocks, and was originally observed in
Labrador.
But while speaking of the material for porce-
lain, we must not overlook the humbler department
of earthenware or pottery. The chief constituents
of clay are silica, alumina, and lime or magnesia.
Potter's clay is the common material used in coarse
pottery, and also for bricks, tiles, and various well-
known purposes. The art of making vessels of
earthenware is a very ancient one, and was car-
ried to a state of perfection by the Greeks and
Etrurians, which later ages were long incapable
of imitating. Here is a picture* of a Greek vase in
which red figures were executed on a background,
and I have many others of a similar kind."
What did the Greeks use these vases for, that
they took such pains to make them nicely ?" said
Mary.
One interesting use was for the preservation of
See page 100.





94 FIrST STEP IN GENERAL KNOWLEDGE

the ashes of their deceased friends. Great num-
bers of funeral urns have been met with in the


ROMAN AMPHOIA.


ancient burial places of various nations. In a tomb
in the Duchy of Nassau, a large urn was found in
the centre, containing the ashes of the burnt body,
and around it were arranged smaller vessels of
various shapes and sizes, which seem to have con-
tained different liquids, such as wine, milk, balm,
oil, &c."
What an odd fancy," said Robert; I wonder




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