Produced by Chris Curnow, Barry Abrahamsen, and the Online
Distributed Proofreading Team at http://www.pgdp.net (This
file was produced from images generously made available
by The Internet Archive)
Useful Knowledge: 4th ed. Minerals. Vol 1 of 3
[Illustration: Frontispiece to Vol. I. see Page 238, 239.
Comparative Height of Mountains, Cities and Lakes
British Islands –– Continent of Europe –– Islands not British –– Asia ––
America
J. Shury sculp.]
────────────────────────────────────────────────────────────────────────
USEFUL KNOWLEDGE:
OR
A FAMILIAR ACCOUNT
OF THE
VARIOUS PRODUCTIONS
OF
Nature,
MINERAL, VEGETABLE, AND ANIMAL,
WHICH ARE CHIEFLY EMPLOYED FOR THE USE OF MAN.
Illustrated with numerous Figures, and intended as a Work both of
Instruction and Reference.
───────
BY THE
REV. WILLIAM BINGLEY, AM. FLS.
LATE OF PETERHOUSE, CAMBRIDGE, AND AUTHOR OF ANIMAL BIOGRAPHY.
[Illustration: Publisher’s Logo]
IN THREE VOLUMES.
VOL. I. MINERALS.
───────
FOURTH EDITION.
───────
LONDON: PRINTED FOR BALDWIN, CRADOCK, AND JOY;
HARVEY AND DARTON;
AND C. AND J. RIVINGTON.
───────
1825.
────────────────────────────────────────────────────────────────────────
C. Baldwin, Printer,
New Bridge─street, London.
────────────────────────────────────────────────────────────────────────
PREFACE.
───────
THE mode in which instruction has hitherto been conveyed, on the
peculiar subjects of the present work, has chiefly been by small books,
in question and answer, denominated catechisms. But such, however
respectable in themselves, or however advantageous for children, are
wholly insufficient for persons who are in search of extended knowledge,
and desirous of furnishing their minds with useful information.
On these subjects there has not hitherto been published any work in
which they are collectively to be found; nor could a knowledge of them
be obtained but by the consultation of many and expensive writings. That
they are generally important to be known will not probably be denied.
It has consequently been the object of the author to compress all the
interesting information that could be obtained respecting them, within
as narrow a compass, and at the same time to render this information as
entertaining, and as devoid of technical words and phrases, as possible.
The scheme of the work will, it is hoped, be found sufficiently simple.
The passage in smaller characters at the head of each article, is in
general so arranged as to reply to the questions, “What is?” “What are?”
or “How do you know?” For instance: “What is flint?” (See Vol. I. p.
53.) The answer will be found thus: “Flint is a peculiarly hard and
compact kind of stone, generally of smoke─grey colour, passing into
greyish white, reddish, or brown. It is nearly thrice as heavy as water,
and, when broken, will split in every direction, into pieces which have
a smooth surface.” The author is aware that, in many instances, the
definitions are defective: but this has, in general, arisen from a
necessity of rendering them short, and at the same time of using such
terms as would be likely to convey information to the minds of persons
who have had no previous knowledge of the systems of natural history.
After the definition, a further illustration sometimes follows; and in
the large characters will be found a brief detail of the history and
uses of the object described. The articles are numbered, for the greater
convenience both of reference and explanation, but particularly the
latter. Thus, under the explanation of CARBON, it is stated that “in
combination with oxygen (21) it forms carbonic acid (26), and that it is
the chief component part of pit─coal (217), petroleum (213), and other
bituminous substances.” By a reference to the numbers inserted, each of
the words, against which they stand, will be explained: whilst at least
three of them would otherwise have been incomprehensible by the
generality of unscientific readers.
It must be remarked that the reader will not here find an account of
every production of nature, which is employed for the use of man, nor
even all the uses of such objects as are described. The most important
of the productions, and the principal of the uses, are all that he
trusts can reasonably be required in a work of the present extent. On
this ground it is that a great number of animals, which are in request
only for food, have been wholly omitted.
The figures that are inserted have been drawn upon as small and
economical a scale as was compatible with a sufficiently accurate
representation of the objects to which they relate. If the reader be
desirous of reference to further illustration, he will derive much
satisfaction from the invaluable figures of Mr. Sowerby in his British
and Exotic Mineralogy, and English Botany, and Woodville’s Medical
Botany; as well as from those in Dr. Shaw’s General Zoology, and
Bewick’s Histories of Quadrupeds and British Birds. There are also many
figures of useful animals in the author’s own work, entitled “Memoirs of
British Quadrupeds.”
────────────────────────────────────────────────────────────────────────
ADVERTISEMENT
TO THE
THIRD EDITION.
Since this work was first printed, the author has made in it
considerable improvements. The first volume, particularly, contains many
additional articles, and more than half of it has been re─written. The
plates also have been re─engraved. For the plate of the mountains a new
drawing has been made, that the scale might be extended, and many
particulars might be introduced which before were omitted. For the
plates of vegetables every drawing has been corrected; and, in place of
such figures as were most defective, new ones have been inserted.
Charlotte─street, Bloomsbury,
London, 1st March, 1821.
────────────────────────────────────────────────────────────────────────
EXPLANATION OF THE PLATES
OF THE
FIRST VOLUME.
───────
FRONTISPIECE.
This is explained in pages 236, 237.
PLATE I.
Fig. MINERAL DEPOSITS.
1. Horizontal beds or strata.
a. Veins or dykes.
2. Bending strata.
3. Minerals in detached masses.
4. Disjoined strata.
b. A fault.
PLATE II.
CRYSTALS, &c.
5. Octohedron.
6. Rough diamond.
7. Profile of a brilliant─cut stone.
8. Profile of a rose─cut stone.
9. Plane of a table─cut stone.
10. Plane and profile of the Pitt diamond.
11. Dodecahedron.
12. Rough garnet.
13. Six─sided pyramids, joined base to base.
14 Regular four─sided prism.
15. Six─sided prism.
16. Cube.
17. Four─sided pyramid having a rhomb for
its base.
PLATE III.
SECTION OF ROCKS.
I. Primitive Rocks.
Fig.
1. Granite.
2. Gneiss.
3. Mica─slate.
4. Clay─slate.
a. Lime─stone.
b. Quartz.
5. Primitive lime─stone.
II. Secondary Rocks.
1. Transition Rocks.
6. Grey─wacka.
7. Transition lime─stone.
2. Floetz Rocks.
8. Old red sand─stone.
9. Alternating strata of lime─stone and
sand─stone.
III. Alluvial Deposits.
10. Alluvial strata of clay, gravel, &c.,
&c.
───────
The BINDER is desired to insert all the Plates, except the
Frontispieces, immediately after the Explanations in the respective
Volumes.
────────────────────────────────────────────────────────────────────────
[Illustration: Pl. 1. Vol. I.
Sections of Strata &c.
J. Shury. sculp.]
[Illustration: Pl. 2. Vol. I.
CRYSTALS &c.]
[Illustration: Pl. 3. Vol. I.
Section of Rocks.
J Shury sculp.]
────────────────────────────────────────────────────────────────────────
USEFUL KNOWLEDGE.
───────
MINERALS.
───────
_INTRODUCTION._
1. MINERALS are natural bodies destitute of organization and life: and
MINERALOGY is that branch of natural science which treats of the
properties and relations of such bodies.
MINERAL DEPOSITS.
2. If we penetrate beneath the surface of the earth, we observe there a
very remarkable arrangement. Instead of a generally uniform appearance,
as we see on the surface, we pass through divers substances, as clay,
gravel, sand, and numerous others, deposited in _beds_ or _strata_ of
various thickness, from a few inches to a great many feet (Pl. I. Fig.
1). These lie, for the most part, nearly horizontal: but in some
instances, particularly in mountainous countries, they take different
degrees of inclination; and, in places where the country consists of
gently sloping hills and vales, the beds have a waving or bending form
(Pl. 1, Fig. 3). The strata of which the earth is composed, as deep as
the curiosity or the necessities of mankind have induced them to
explore, satisfactorily demonstrate the wisdom which has been displayed
in the arrangement of materials requisite for the use of men and
animals.
The first layer is frequently a rich, black mould, formed almost wholly
of animal and vegetable remains. This yields sustenance to the vegetable
productions; and thereby becomes the actual, though not the immediate,
support of the whole animal creation.—Beneath this is often found a
thick bed of clay, that furnishes to man a substance of which to make
bricks, tiles, various kinds of pottery, and innumerable other articles
for the comfort of social life.—Next are deposited vast beds of gravel,
that are of use in numerous points of view.—Underneath this are the
infinitely varying strata of sandstone, limestone, &c. which not only
serve for the construction of buildings, and for other important
purposes, but also frequently surround mines which contain the valuable
metals.—Beneath a slaty stratum are usually discovered those immense
beds of coal so requisite for the comfort, and, in some situations, even
for the existence of man.
These strata, it is true, are not always found together, nor are they
always discovered in the same order; but the statement will suffice to
show the general nature of their arrangement.
3. Minerals are sometimes observed in detached _masses_ of various size,
and situated at various depths in the earth (Pl. I, Fig. 1).
4. They are also found in a kind of natural clefts which cross the
regular mineral beds or strata in different directions (Pl. I, Fig. 1,
_a_, Pl. I, Fig. 4, _b_). When these contain metallic ores, they are
styled _veins_; but when they contain only stony or earthy matters, the
miners call them _dykes_. They vary much both in magnitude and length.
Six thousand feet are considered an unusual length for veins, though, in
some instances, veins have been traced upwards of four miles. Few veins
extend more than 1200 feet below the surface of the mountains in which
they are situated. They are usually much inclined; but they sometimes
descend in a direction parallel with the beds of rock in which they
occur.
5. At the places where dykes or veins pass through the earth, they
occasionally disjoint the strata in a very singular manner (Pl. I, Fig.
4). Some of the coal strata, for instance, are thrown down or raised on
one side of a dyke upwards of a hundred yards; and the miner, after
penetrating through this dyke, instead of finding the same coal again,
meets, on the opposite side, with beds of stone or clay. Hence he is
frequently at a loss how to proceed in searching for the coal of which
he is in pursuit; and hence it is that to such dykes the peculiar name
of _faults_ has sometimes been given.
6. In England the _metallic ores_ are generally found in veins, that
form a considerable angle with the regular strata. This in Cornwall is
uniformly the case. And it is remarkable, concerning the veins of tin
and copper of that county, that they run in a direction nearly east and
west; whilst the dykes, or veins of other substances, run for the most
part north and south.
7. The thickness of veins, and the quantity and quality of the ores they
contain, differ in every mine. Some are only a few inches wide, whilst
others extend to the width of several feet. The vein at Dalcooth mine,
in Cornwall, varies from two or three to forty feet and upwards; and, in
some parts, it contracts so as to be little more than six inches across.
8. In Cornwall the first traces of tin and copper are usually found at
the surface of the ground, and thence to the depth of 80 or 100 feet
beneath; and it is said that no miner has ever yet seen the bottom of a
vein, although several have been wrought to the depth of more than 1000
feet. The veins of these metals have, in some instances, been worked to
the length of three or four miles.
9. It is frequently observed that metallic veins are separated, from the
substances they intersect, by a thin wall, or lining, of minerals
different from these substances, and also by a layer of clay on each
side of the vein. It is also remarked that the same substance which
forms the outer coat of the vein is often intermixed with the ore, or
forms layers alternately with it. This has usually the denomination of
_matrix_ or _gangue_.
10. There are few mines of any considerable depth that would not be
flooded with _water_ from internal springs were not means adopted for
drawing off this fluid. The steam engines that are employed for this
purpose in some of the Cornish mines are so powerful as to discharge
incessantly, both by night and day, a quantity of water, equal to at
least 1000 gallons, or near twenty hogsheads, every minute.
SYSTEMATIC ARRANGEMENT OF MINERALS.
11. To a superficial observer, perhaps nothing would appear more easy
than to describe a mineral. This, however, is by no means the case. The
same general appearance sometimes prevails in substances that are very
different from each other; and the same stone, in its different states,
is often extremely varied in its appearance. To these difficulties it
must be added, that the combinations of mineral substances are
multiplied to a great extent. A little application, however,
particularly if the student be possessed of a collection of arranged and
named specimens, which he will have no difficulty in procuring at a
reasonable price, will enable him to overcome all the obstacles that
otherwise might impede his progress in beginning to acquire a knowledge
of this interesting science.[1]
12. The most simple and natural division of minerals is into four
classes, of, 1. STONES; 2. SALTS; 3. COMBUSTIBLES; and, 4. METALS; and
the following table, which has chiefly been arranged from the system of
Werner, the well─known German mineralogist, will exhibit a tolerably
correct outline of the classification of these substances. To reduce the
whole within the compass of a single page, many of the families,
however, have necessarily been omitted.
Footnote 1:
Such collections are supplied by Mr. Mawe, No. 149, Strand, London.
His terms, for collections containing from 100 to 200 specimens, are 5
guineas; from 200 to 300 specimens, 10 guineas; and from 300 to 400
specimens, 15 guineas. For collections containing from 350 to 400
specimens, more select, and comprising a better suite of precious
stones, he charges from 20 to 30 guineas; and for larger collections,
from 50 to 100 guineas. At the particular request of the author, Mr.
Mawe has arranged a few collections of minerals, and numbered them in
such manner as to correspond with, and illustrate the present volume.
────────────────────────────────────────────────────────────────────────
PRINCIPAL SPECIES.
{ Diamond. _Diamond_.
{
{ Zircon. _Jargoon_.
{
{ { _Oriental sapphire_.
{ Ruby. { _Oriental ruby_.
{ Scratch { { _Emery_.
{ glass. {
{ { Schorl. { _Topaz_.
{ { { _Emerald_.
{
{ { Garnet. _Precious garnet_.
{
{ { { _Crystal_.
{ { Quartz. { _Flint_.
{ I. EARTHY. { { { _Agate_.
{ { { _Opal_.
{ {
{ { { Clay. _Pure clay_.
{ { { Clay slate. _Roofing slate_.
{ { Will not { Mica. _Muscovy glass_.
{ { scratch { Soapstone. _Fuller’s earth_.
{ I. STONES { { glass. {
{ { { Talc. { _Talc_.
{ { { _Asbestos_.
{ {
{ { { _Limestone_.
{ { { Lime. { _Phosphat of lime_.
{ { { { _Fluor spar_.
{ { II. SALINE. { { _Alabaster_.
{ {
{ { Barytes.
{ { Strontian.
{
{ { Alumine. _Alum_.
{ {
{ { Magnesia. _Epsom salt_.
{ {
{ II. SALTS. { Soda. { _Common salt_.
{ { { _Borax_.
{ {
{ { Potash. _Nitre_.
{ {
{ { Ammonia. _Sal─ammoniac_.
{
{ { Sulphur. _Sulphur_.
{ {
{ { { _Naphtha_.
{ III. COMBUSTIBLES { Bitumen. { _Coal_.
{ { { _Jet_.
{ {
{ { Graphite. _Black─lead_.
{ {
{ { Resin. _Amber_.
{
{ { Platina. _Platina_.
{ { Gold. _Gold_.
{ { Mercury. _Mercury_.
{ { Silver. _Silver_.
{ { I. MALLEABLE. { Copper. _Copper_.
{ { { Iron. _Iron_.
{ { { Tin. _Tin_.
{ { { Lead. _Lead_.
{ IV. METALS. { { Nickel. _Nickel_.
{ { Zinc. _Zinc_.
{
{ { Arsenic. _Arsenic_.
{ { Bismuth. _Bismuth_.
{ II. BRITTLE. { Cobalt. _Cobalt_.
{ Manganese. _Manganese_.
{ &c. &c.
13.To complete a general view of the different productions of the
mineral kingdom, it is requisite to subjoin a tabular arrangement of the
various kinds of _rocks_.
SPECIES.
{ 1. Granite.
{ 2. Gneiss.
{ 3. Mica slate.
{ 4. Clay slate.
{ 5. Primitive limestone.
{ 6. Primitive trap.
{ 7. Serpentine.
{ I. PRIMITIVE. { 8. Porphyry.
{ { 9. Sienite.
{ {10. Topaz rock.
{ {11. Quartz rock.
{ {12. Primitive flinty slate.
{ {13. Primitive gypsum.
{ {14. White stone.
{
{ { 1. Transition limestone.
{ { I. TRANSITION { 2. Transition trap.
{ { ROCKS. { 3. Grey wacke.
{ { { 4. Transition flinty slate.
{ { { 5. Transition gypsum.
{ {
{ II. SECONDARY. { { 1. Old red sandstone.
{ { { 2. Floetz limestone.
{ { { 3. Floetz gypsum.
{ { { 4. Second, or variegated sandstone.
{ { { 5. Second floetz gypsum.
{ { II. FLOETZ { 6. Shell limestone.
{ { ROCKS. { 7. Third sandstone.
{ { 8. Rock salt.
{ { 9. Chalk.
{ {10. Floetz trap.
{ {11. Coal.
{ {12. Newest floetz trap.
{
{ { 1. Peat.
{ { 2. Sand and gravel.
{ III. ALLUVIAL. { 3. Loam.
{ { 4. Bog iron ore.
{ { 5. Calcareous tufa, &c.
{
{ { 1. Burnt clay.
{ { I. PSEUDO VOLCANIC { 2. Porcelain jasper.
{ { ROCKS. { 3. Earth slag.
{ { { 4. Columnar clay ironstone.
{ IV. VOLCANIC. { { 5. Polishing slate.
{
{ II. TRUE VOLCANIC { 1. Stones and ashes.
{ ROCKS. { 2. Lava.
{ 3. Matter of muddy eruptions.
14. For the purpose of ascertaining the names and characters of
minerals, attention must be paid to their _form_, _surface_, _lustre_,
_fracture_, or the appearance of their internal surface when broken;
_structure_, _transparence_, _streak_, or the mark left when scratched
by any hard body; _stain_, or trace left when rubbed upon paper;
_cohesion_, whether solid, friable, or fluid: _hardness_, or the
resistance which they oppose when scratched; _tenacity_, or the
resistance which they oppose to the stroke of a hammer; _flexibility_,
or their property of bending without breaking; _feel_, or the sensation
communicated by their surfaces when handled; _smell_, _taste_,
_adherence to the tongue_, _sound_, _specific gravity_, or weight in
comparison with that of water; _colour_ and _electricity_.
15. To ascertain the _chemical properties_ of minerals, one of the most
important instruments is the blow─pipe. This is a tube which terminates
in a cavity as fine as a small wire, and through which the air is
forced, and made to play upon the flame of a candle. The flame is thus
concentrated, and directed against small particles of the mineral to be
examined, which is placed upon a bit of charcoal in a spoon of platina
or silver. The air is forced into the blow─pipe by the mouth of the
person using it, or by bellows attached to it for that purpose. Under
this operation we have an opportunity of trying the action of other
bodies upon minerals at a very high temperature; and the properties
which these experiments bring into view enable us, in many cases, to
ascertain, not only the nature, but even the component parts, of
minerals.
SIMPLE MINERAL SUBSTANCES.
16. As a necessary introduction to the study of minerals, it is
requisite to describe, in a brief manner, such simple substances as form
their constituent parts. Few of these, it is true, are to be found in a
separate, uncombined state; yet that they do exist, and that they are to
be obtained from the minerals with which they are united, we have the
proof of every day’s experience.
UNCONFINABLE FLUIDS.
17. There are some kinds of unconfinable fluids, the existence even of
which is manifested only by their contact with other bodies, or becoming
separated from them. They are of a nature too subtile to be collected or
confined in our vessels for the purpose of examination, and the
investigation of their properties has consequently been attended with
peculiar difficulty. Those at present known are _caloric_, _light_,
_electricity_, and _magnetism_; but of these the first only is
immediately connected with the subjects of our present investigation.
18. _Caloric_.—Every one is acquainted with the different sensations of
heat and cold. That matter which produces on our bodies the sensation of
_heat_ has the name of _Caloric_; heat being only an effect, of which
caloric is the cause. This is extended in a greater or less degree
through the whole extent of space, and penetrates into the interior of
even the most solid bodies: in so doing it expands the particles of
which they are composed, augments their bulk, and diminishes their
solidity. The sun is the principal fountain from which the earth is
supplied with this fluid; and it passes thence to us at the rate of
12,000,000 of miles per minute. The defect of caloric in any substance
occasions the sensation called cold.
Were the world deprived of caloric, every species of organized being
would, from that moment, cease to exist. It is the cause of all
fluidity: to it every production of the earth has been most essentially
indebted, even for its form and structure; and in no respect do the
power and goodness of the Almighty appear more conspicuous than in the
creation, dispersion, and continuance, of this most subtile and
astonishing fluid.
19. All the various substances with which we are acquainted must be
considered either as solid or fluid. Every substance is defined to be a
_solid_ in which the parts are so united or connected that it requires
an external force to separate them. A _fluid_, on the contrary, is a
body the parts of which are so loosely connected that they not only
yield easily to any force impressed upon them, but also move freely
amongst each other; and every fluid is a combination of caloric with
some other substance.
20. Fluids are of two kinds: one of these, called _liquids_, have, when
at rest, a smooth and distinct surface, and are distinguishable both by
the sight and touch; the other, denominated _gas_, or _gaseous fluids_,
have the appearance of air, and are not perceptible either to the sight
or touch, except under certain circumstances. The latter are principally
oxygen (21), azote or nitrogen, and hydrogen (45). We shall at present
have occasion to speak only of the first.
GASEOUS FLUIDS.
21. _Oxygen_, like caloric, is a fluid never found in an uncombined
state. It forms one of the component parts of the air that we breathe,
and of the water we drink; but it approaches nearest to a state of
purity in combination with caloric (18), when it has the name of _oxygen
gas_. It was formerly called _vital air_, because no breathing animal
can live for a moment in any air or gas which has not in it a mixture of
oxygen; every kind of combustible burns with great splendour in it, and
without it ceases to burn. It unites with a great number of substances,
and changes both their appearance and properties in a very remarkable
manner. Of the metals it entirely destroys the metallic lustre, and
gives them an earthy form and texture. Substances in this state have the
name of _oxides_.
Lead, for instance, combined with oxygen becomes the well─known red and
heavy substance used by painters, under the name of minium or red lead
(239). This, if deprived of its oxygen, loses its red colour, and
returns to its former metallic state. Some of the metals are oxidized by
merely being exposed to moisture. Thus the rust which is so readily
contracted by iron is an oxide of that metal, produced by its attracting
oxygen from the air or from water.
ACIDS.
22. It is one of the most remarkable properties of oxygen to impart to
most of those bodies called _acids_ their peculiar character of acidity.
Oxygen does not itself possess the properties of an acid, nor is it an
essential ingredient in all acids, though it is the acidifying principle
in the greater number of them.
23. _Acid_ is a word originally synonymous with sour. It has, however,
been gradually extended in its signification, and now comprehends all
substances possessed of the properties of exciting upon the tongue the
sensation called sour; of changing the blue colours of vegetables to
red; of uniting with water in almost any proportion; of combining with
alkalies (42), metallic oxides, and earths, and of forming with them
certain compounds called _salts_.
24. _Sulphuric Acid_, or _Spirit of Vitriol_, as it is commonly called,
is a liquid of a somewhat oily consistence, transparent and colourless
as water, formed by a combination of oxygen (21) with sulphur (46). Like
other acids, it never occurs in nature in a pure state, for it can no
sooner be formed than it unites with earths (31), alkalies (42), or
metals, and forms, with them, several well─known salts, which have the
name of _sulphats_. Thus alabaster (192) and Epsom salts (199) are
respectively formed by an union of sulphuric acid with lime and
magnesia, and are denominated by chemists sulphat of lime and sulphat of
magnesia. In like manner, blue vitriol (209) is sulphat of copper; green
vitriol (208), sulphat of iron; and white vitriol (210), sulphat of
zinc.
25. _Phosphoric Acid_ is produced by a combination of oxygen (21) with
phosphorus (47); and, when obtained in a state of purity, is not a
fluid, but a white and flaky substance. This acid, when combined with
mineral productions, forms those salts which have the name of
_phosphats_. It is very soluble in water; and, in dissolving, makes a
hissing noise, similar to that produced by plunging hot iron into water.
26. _Carbonic Acid_ is a compound of oxygen (21) and carbon, or pure
charcoal (48): and in a state of gas (20) it forms a constituent part of
the atmospheric air. It is also emitted in great abundance from wine,
beer, and other liquors, in a state of fermentation, and is sometimes
found in the lowest parts of mines, where it is known to the miners by
the name of _choke damp_, from the circumstance of its immediately
extinguishing flame, and suffocating all animals that are immersed in
it. This gas, which was formerly called by chemists _fixed air_, is
about twice the weight of common air. In combination with lime it forms
chalk, marble, and limestone; and it constitutes part of several other
mineral substances, which are thence denominated _carbonats_.
27. _Fluoric Acid_ is a gas of very singular nature, which is held in
combination with lime, in the Derbyshire or fluor spar (194); and may be
separated from it by pouring sulphuric acid, or spirit of vitriol (24),
upon powdered spar, in a leaden vessel called a retort, and applying to
it a gentle heat. The salts formed by fluoric acid have the name of
_fluats_.
28. The _Boracic_ is a peculiar kind of acid, which, in combination with
soda (200), forms the substance that we import from the East Indies
under the name of borax (204). When extracted from borax this acid does
not assume the form of a fluid, but appears in thin six─sided scales or
flakes, of white colour, which adhere slightly together, and feel
somewhat greasy in handling. To the taste it is at first sour, then
bitterish; and at last it leaves an agreeable sweetness on the palate.
29. _Muriatic Acid_ is a gas formed by the combination of oxygen (21)
with some base that is not yet known. It is an invisible and elastic
fluid, which, in mechanical properties, resembles common air, and has a
pungent and very peculiar smell. This gas unites with alkalies (42),
earths (31), and the oxides (21) of metals; and with them forms the
compounds called _muriats_, of which common salt, or muriat of soda
(202), is one of the principal. The liquid muriatic acid, or muriatic
acid gas combined with water, is frequently denominated _spirit of salt_
(202).
30. _Nitric Acid_ is a compound of oxygen and azote, or nitrogen, in the
proportion of twenty─five parts, by weight, of the latter to
seventy─five of the former. It is one of the constituent parts of nitre,
or saltpetre (206); and, in a pure state, is transparent and colourless,
like water. By the action of light, however, it soon becomes yellow;
and, if exposed to the air, it emits yellow fumes, which even tinge the
air of the same colour. To the taste it is extremely acid. It dyes the
skin a yellow colour, which is very difficult to be removed; and it is
so corrosive as to destroy almost every substance into which it
penetrates. If poured upon oils, it sets them on fire. With various
bases it forms compounds called _nitrats_. This acid, which hitherto has
never otherwise been obtained than mixed with water, is chiefly known in
commerce by the name of _aqua fortis_ (206).
EARTHS.
31. The solid contents of the globe are composed of several elementary
substances, amongst which have been enumerated no fewer than nine
different kinds of earth:
1. Silex.
2. Alumine.
3. Zircon.
4. Glucine.
5. Yttria.
6. Barytes.
7. Strontian.
8. Lime.
9. Magnesia.
These, when freed from foreign admixture, are, for the most part, of
white colour, not soluble in water, not combustible, and do not exceed
four times the weight of water.
32. The whole of these earths have, till lately, been considered simple
and uncombined substances; but, by the discoveries of Sir Humphrey Davy,
it has been ascertained that four of them have a metallic basis, and are
in fact metallic oxides, or compounds consisting of a metal united with
oxygen (21). These, which have the same affinity with their respective
bases as rust has to iron, are silex, lime, barytes, and alumine. Until,
however, some further light be thrown upon their nature and
constitution, they must continue to hold their former situation of
simple earths.
33. _Silex_, or _Siliceous Earth_, is the basis of all substances known
by the name of quartz and silex (76). In a state of nature it has never
been found pure; but, in combination with other substances, it abounds
in almost every country of the globe. Common flint (90) contains
ninety─seven parts in a hundred of silex: it consequently has given its
name to this earth, _silex_ being the Latin word for flint. When
purified it is a white powder, the particles of which are harsh to the
touch, as if they consisted of very minute grains of sand. It is not
quite three times as heavy as water, and has neither taste nor smell.
Water will not dissolve it, nor any kind of acid, except fluoric. Sir H.
Davy has discovered it to have a metallic basis, to which he has given
the name of _silicium_.
34. _Alumine_ is a kind of earth, so called from its forming the basis
of alum (197). It is soft, compact, and tenacious; about twice the
weight of water, and, when breathed upon, has a smell which is peculiar
to all clayey productions. In the fire it shrinks, and becomes so hard
as even to yield sparks when struck against steel. It readily absorbs
water, and is dissolved by most acids. Some writers state that pure
alumine has been discovered in a native state near Halle, in Germany. It
is found in a crystallized form, and nearly in a state of purity, in the
Oriental ruby and sapphire. The name of _argil_, or clay, has sometimes
been applied to it; but, in mineralogy, this name has usually been given
to a mixture of alum, quartz, and other substances. Sir H. Davy has
obtained from alumine a metallic basis, called _aluminum_.
35. _Zircon_, when freed from those substances with which it is
combined, is a white and somewhat rough powder, insipid to the taste,
insoluble in water, and about four times as heavy as that fluid. It is
found in the two kinds of precious stones called jargoon and hyacinth,
and has not hitherto been applied to any useful purpose.
36. _Glucine_ is a kind of earth of peculiar nature, which is found in
the emerald and beryl, and, when purified, forms a soft and white
powder, without smell, and of sweetish taste. To the last of these
qualities it is indebted for its name, which is derived from a Greek
word signifying sweet. It is somewhat unctuous to the touch, and about
three times as heavy as water. The uses of this earth, whatever they may
be, are not known.
37. _Yttria_ is an earth which, among other particulars, differs from
glucine by its weight, as it is nearly five times heavier than water. In
a natural state it occurs as the basis of a black Swedish mineral,
called gadolinite. When cleansed, by chemical process, from all its
impurities, it is a fine, white, and inodorous powder.
38. _Barytes_ is a white, porous, and very heavy earth, which can only
be obtained pure by chemical process. It is easily reduced to powder,
and is soluble in all kinds of acids. To the taste it is harsh and
caustic; and, if taken into the stomach, proves an extremely virulent
poison. In some respects it agrees with the alkalies (42), particularly
in its property of changing blue vegetable colours to green, and in
corroding, like them, though with less energy, all kinds of animal
substances. From these circumstances it has sometimes been denominated
an alkaline earth. Saturated with sulphuric (24) and carbonic acid (26),
it constitutes the minerals denominated sulphat and carbonat of barytes
(196). It has been discovered to have a metallic base, which is called
_barium_.
39. _Strontian_ is an earth which, like barytes, is not found otherwise
than in combination with sulphuric and carbonic acids. It occurs in
various parts of the world, and, when purified, forms a porous mass of
greyish white colour, acrid taste, and somewhat alkaline nature. This
earth converts vegetable blue colours to green, but does not act so
strongly on animal bodies as barytes, nor is it poisonous, like that
substance.
40. _Lime_, the basis of all those substances which are denominated
_calcareous_, is only to be obtained in a state of purity by artificial
process. Combined with carbonic acid (26) it forms limestone (140),
chalk, and marble; all of which are capable of being converted into lime
by burning. Lime may also be obtained from oyster and other sea shells.
When pure, it is of white colour, and moderately hard substance, though
it is easily reducible to powder. Its taste is burning and acrid; and,
like the alkalies, it changes vegetable blue colours to green. It has
likewise the property of corroding and destroying animal substances.
Lime, when pure, absorbs water rapidly, becomes hot, and falls into
powder. Even if exposed to the open air it gradually attracts moisture,
and assumes a powdery form; soon after which it becomes saturated with
carbonic acid (26) from the atmosphere, and is thereby again converted
into carbonat of lime (140). It occurs abundantly in almost every
country, but always in combination with some acid, carbonic (26),
sulphuric (24), boracic (28), fluoric (27), or phosphoric (25). This
substance has a metallic basis, which has been denominated _calcium_.
41. _Magnesia_ is a light and perfectly white kind of earth, of soft
powdery appearance, without taste or smell, and somewhat more than twice
as heavy as water. It is not found in this pure state in nature, but may
be prepared from Epsom salt, which consists of magnesia in union with
sulphuric acid (24). The slightly acrid taste that is perceptible in the
magnesia used in medicine arises from a portion of lime which it
contains. This substance does not dissolve in water, but is soluble in
every kind of acid. It has the property of changing delicate blue
colours to green.
ALKALIES.
42. Alkalies are substances which enter into the composition of several
kinds of minerals, and are known by their property of changing the
colour of blue vegetable juices to green, and by a peculiarly acrid,
caustic, and nauseous taste, which it is impossible to describe, but
which, after it has been once experienced, will easily be recollected.
Alkalies corrode and dissolve animal substances, and unite with oil and
fat in such manner as to form the well known compound called soap. They
readily dissolve in water; and, when mixed with acids, form what have
been denominated neutral salts.
43. The alkalies at present known are three in number; _potash_ (205),
_soda_ (200), and _ammonia_ (207). Of these the two former, although
till lately they have been considered simple substances, have been shown
by Sir H. Davy to have metallic bases.
SIMPLE COMBUSTIBLES.
44. By this term we are to understand all those mineral substances,
capable of combustion, which have not been discovered to consist of more
than a single component part. They are four in number; _hydrogen_,
_sulphur_, _phosphorus_, and _carbon_.
45. _Hydrogen_, as its name imports, is a principal constituent part of
water; for, singular as it may appear, that well─known fluid is formed
by a combination of two species of air or gas, called hydrogen and
oxygen (21), and in the proportion of about fifteen parts of the former
and eighty─five parts of the latter. This gas had formerly the
denomination of _inflammable air_, and has long been known in mines
under the name of _fire─damp_. It is about twelve times lighter than
atmospheric air. When pure it soon destroys such animals, and
extinguishes all such flaming substances, as are immersed in it. Mixed
with atmospheric air, it explodes with great violence on the application
of any ignited body.
46. _Sulphur_ is a simple combustible substance, of yellow colour, which
is found pure, or native, in several parts of the world, and is
sufficiently familiar to us under the name of _brimstone_ (211). It
strongly attracts oxygen (21), and is thereby converted into sulphuric
acid (24). It frequently occurs in combination with mineral substances,
such as arsenic, antimony, copper, and other metallic ores.
47. _Phosphorus_ is a combustible substance which, when pure, somewhat
resembles bees’─wax both in colour and consistence; and, when exposed to
the air under the usual temperature of our atmosphere, is luminous in
the dark, and has a smell somewhat resembling that of garlic. It is so
combustible that, when melted, it should be kept under water, as it
cannot be exposed to the air during this process without great risk of
catching fire. This substance is not known in a native state; and the
whole of what is used in philosophy and commerce is obtained by
different artificial processes. In union with oxygen (21) it becomes
converted into an acid, called _phosphoric acid_ (25), and, under this
form, in conjunction with lime, it constitutes the bones of men and
animals. The greater part of the phosphorus of the shops is obtained
from bones.
48. _Carbon_ is a name given to the pure inflammable part of charcoal.
It is abundantly diffused throughout nature, for it enters into the
composition of several minerals, and of all vegetable and animal bodies.
The purest form under which carbon is known to exist is in the diamond
(50). It may, however, be obtained sufficiently pure, for all common
purposes, by burning a piece of wood, covered with sand, in a vessel
called a crucible. In combination with oxygen (21) it forms carbonic
acid (26). Carbon is a chief component part of pit─coal (217), petroleum
(213), and other bituminous substances.
────────────────────────────────────────────────────────────────────────
CLASS I.—STONES.
ORDER I.—EARTHY STONES.
───────
_I. HARD: those which scratch Glass._
───────
49. OF GEMS IN GENERAL.
Gems, or precious stones, as they are frequently called, are, for the
most part, transparent, and have a vitreous or glassy appearance. Their
different colours are occasioned by metallic oxides (21) of various
kinds, with which they are impregnated. Some writers have classed them
by their colours, but this is a very uncertain mode, as different gems
have not unfrequently the same colour; and, in many cases, the same gems
are of different colours. The usual distinction of gems into Oriental
and Occidental is also liable to error, as the best gems, from whatever
part of the world they are brought, are always called Oriental. The most
estimable of all the kinds are the diamond (50), ruby (54), emerald
(67), and sapphire (53); and stones a grain in weight, and equal in
quality, are valued in the following proportions, at 8_l._ per carat for
diamonds, 4_l._ for rubies, and 3_l._ for each of the others. The
amethyst (79), topaz (61), and aqua─marine (61), are considered of
nearly equal value with each other; and the garnet (70) is the cheapest
of precious stones.
The ancients engraved upon several kinds of gems; but they appear to
have been ignorant of the art of cutting the diamond, the ruby, and the
sapphire, which were too hard for them to operate upon. The emerald and
the noble opal (102) were too highly esteemed as precious stones to have
often found their way into the hands of engravers. It has been asserted
that the ancients did not use the topaz for engraving; but there is
extant a beautiful _intaglio_, representing an Indian Bacchus, which is
said to be a topaz. The garnet was often engraved upon: and there are
many master─pieces of the art in calcedony (91) and carnelian (93.) Onyx
and sardonyx (92) were employed for that species of engraving in relief
called _cameos_; and, in many instances, it is pleasing to observe with
what dexterity the ancient artists availed themselves of the different
colours in the alternate zones to express the different parts and shades
of their figures.
Most of the gems may be imitated by artificial preparations of glass,
coloured by different metallic substances; and it is not easy, by mere
inspection, to distinguish the better kinds of factitious stones from
real gems. They are, however, discoverable by a deficiency of lustre,
and being so soft as, even in the most perfect kinds, to yield to the
point of a steel instrument.
The cutting and polishing of gems is the work of the lapidary, and is in
general thus performed:—The shape most proper to be given to any
particular gem being determined on, the stone is cemented to the end of
a stick, and the different facets are formed by a mill contrived for the
purpose. This mill is a plate of copper, or an alloy of lead and tin, to
which an horizontal motion is given by very simple machinery, and the
surface of which is charged either with diamond powder and oil, or with
fine emery and water. A thick peg of wood called a gauge, pierced with
small holes in all directions, is set upright on the lapidary’s bench,
close to the mill, and the process of shaping the facets thus takes
place. The stone is placed on the surface of the mill, the opposite end
of the stick to which it is cemented being inserted in one of the holes
of the gauge. In this position it is kept steady by the workman, with
his right hand, whilst, with the other, he puts the mill in motion. The
skill of the lapidary depends on regulating the velocity of the mill,
and pressing with more or less force on the stick, with an almost
imperceptible tendency to one or other direction in different stages of
the work, examining each facet at very short intervals, in order to give
as great precision as possible to its size and form. This part of the
business being completed, the cutting mill is taken out, and replaced by
one of brass, on which the polishing is performed by means of fine emery
(58), tripoli, and rotten stone (119), exactly in the same manner as is
practised in the first stage of the process for setting the facets.
DIAMOND.
50. _The DIAMOND, or ADAMANT of the ancients, is the most valuable of
gems, and the hardest of all known bodies; when pure, it is perfectly
transparent._
_In a rough state, diamonds have usually either the form of rounded
pebbles, with a shining surface, or they are crystallized in the shape
of octohedrons, or double four─sided pyramids. (Pl. II, Fig. 5, 6.)
Though for the most part colourless, they are sometimes yellow, green,
blue, blackish, or rose─coloured._
The best diamonds are brought from the East Indies. The principal mines
are those of Raolconda and Coulour, in the province of Golconda; and
that of Soumelpour, or Goual, in Bengal. At Raolconda they are found in
the deep crevices of rocks. Persons, by means of long iron rods, with
hooks at the end, draw out from these crevices the loose contents, and
afterwards wash them in tubs, for the purpose of discovering the
diamonds.
The first discovery of diamonds at Coulour was about two centuries ago,
by a countryman, who, on digging his ground to sow millet, accidentally
found one of these stones of large size. From that period the whole
adjacent plain began to be searched to the depth of from ten to fourteen
feet; and the work was, at one time, so extensively pursued, that nearly
6,000 persons were employed in it. At Soumelpour the diamonds are found
amongst the sand and gravel of the river.
Diamonds are likewise found in the island of Borneo, and in several
parts of South America. The mode by which they are obtained from one of
the rivers of Brazil has been described by Mr. Mawe. The current is
turned, and part of the bed of the river being laid dry, the mud is
taken up and washed, by negroes, in places prepared for the purpose,
through which a portion only of the stream is allowed to flow. As soon
as all the earthy particles have been washed away, the gravel─like
matter that remains is raked together, the stones are thrown out, and
what diamonds happen to be present are found amongst the refuse that is
left.
To ascertain whether a stone, that has been found, be really a diamond,
the workmen have a mode of placing it upon a hard substance, and
striking it with a hammer. If it either resists the blow or separate
into leaves, it must be a diamond; but, in the latter case, the
discovery is sometimes made at an immense expense, as, by thus
diminishing the size, its value must also, of course, be greatly
diminished.
Diamonds are generally exported from Madras in a rough state; and in
small parcels neatly sewed in muslin, and sealed by the merchants who
send them. These, we are informed by Mr. Milburne in his valuable work
on oriental commerce, are, for the most part, sold in Europe by the
invoice, as it is called; that is, without being opened: and he says
that they are always found to contain the value for which they were sold
in India.
Of all transparent substances, none for brilliancy can be compared with
the diamond. Its hardness is such, that no steel instrument whatever can
make any impression upon it. Notwithstanding this, at a temperature not
so high as that which is required for the melting of silver, it
gradually dissipates and burns. Diamonds have been shown to consist
principally of carbon or charcoal in a pure and crystallized state.
The ancients, ignorant of the art of cutting diamonds, were contented to
set them in a native state; and for this purpose they preferred such
stones as had naturally a crystallized form. The four large diamonds
which ornament the clasp of the Imperial mantle of Charlemagne, and
which are still preserved in Paris, are uncut stones of this
description. The extreme hardness of the diamond baffled all attempts to
polish it in such manner as to exhibit its peculiar beauty, until the
year 1456, when a young man of Bruges, whose name was Berquin,
endeavoured to polish two diamonds by rubbing them against each other.
Having succeeded in this, he next constructed a wheel, on which, by
means of diamond powder, he was enabled to cut and polish these gems in
a manner beyond his greatest expectation. Since this period the art of
polishing them has been greatly improved both by the Dutch and British
jewellers.
In the choosing and valuing of diamonds in a rough state, attention is
paid to their colour, their being free from extraneous matter, and their
shape. Those that are most perfect are crystalline, and resemble a drop
of clear spring water, in the middle of which is to be perceived a
strong light, that plays with great spirit on moving them about. When
they have a yellowish or greenish tinge they are considered to be bad.
Many diamonds have a kind of confused structure, which lapidaries
compare to knots formed in wood. These are rejected, from the
impossibility of polishing them properly.