hardness, it is very difficult to be cut and polished; and even the best
polish which it is capable of taking as so imperfect, that a person
ignorant of its nature might consider it to be merely smoothed and
rubbed with oil. The ancient artists executed in it many beautiful and
delicate figures; and it is impossible but to admire the industry and
perseverance by which they produced even chains, and other hollow kinds
of work, in jade.
The Turks cut it into handles for sabres and daggers, and into several
kinds of vessels, to which they attach great value.
Jade occurs in granite (251) and gneiss (255) in Switzerland; but the
most beautiful specimens of this mineral are brought from Persia, Egypt,
and Siberia.
131. AXESTONE _is a kind of jade, but differs from it in having a slaty
texture; and in being less transparent and less tough_. This stone is
found in China, New Zealand, and on the banks of the river of Amazons,
in America. And it is said that several of the tribes of American
Indians form of it the axes which they use in place of iron. To explain
how these people have been enabled to work a substance so rebellious as
this is even to the file, and to other instruments of steel (of which
they know not the use), it has been presumed that, when the stone is
first taken from the earth, it is considerably less hard than when, by
drying, its humidity is evaporated: that in this state they work it, and
subsequently harden it, in some peculiar manner, by exposure to heat.
132. _SERPENTINE is a stone which, when polished, has a near resemblance
to marble, is of dark green colour, or reddish; variously streaked, and
spotted with lighter green, red, brown, and yellow._
_It is found in beds, and in a massive state; is translucent at the
edges; and, when pounded, the powder feels soapy to the touch._
There are few stones likely to prove more valuable in ornamental
architecture, both for beauty and durability, than this. It admits of an
excellent polish, which is not easily injured by the effects of air or
water. It is also too hard to suffer the same inconveniences of being
scratched or broken as marble; and its colours are stated to be
indestructible. And such is the size of many of the blocks of
serpentine, that columns of almost any dimensions may be wrought out of
them.
Of the serpentine obtained from the Island of Anglesea, and lately known
by the name of _Mona marble_, a great proportion was sent to London by
Messrs. Bullock and Co. who, until the death of Mr. Bullock, had a large
warehouse and polishing rooms for it in Oxford─street. The prevailing
colours of this stone are red and green. The quarries were worked by
them to considerable extent. They manufactured it into chimney pieces,
slabs, columns, and other articles; and its great beauty, and its
excellence, in many respects, over the generality of marbles, will
recommend it strongly to the public notice.
The chief places in which serpentine has hitherto been found are near
Bareuth, and Zöblitz, in Saxony; in some districts of Cornwall; about
six miles west of the Paris copper mine, in the island of Anglesea; at
Portsoy, in Bamffshire, and other parts of Scotland; and at Cloghan Lee,
in the county of Donegal, Ireland.
At Zöblitz there are some extensive manufactories, in which serpentine
is made into vessels and ornaments of various shapes, that are carried
for sale over nearly all parts of Germany. Several hundred persons are
there employed in the working of this stone.
The name of serpentine is derived from some of the varieties appearing
coloured and spotted like a serpent’s skin. This stone, when found
intermixed with primitive limestone, or crystalline white marble,
differs in no respect from the celebrated _verde antique_ marble (149).
133. _POTSTONE, or LAPIS OLLARIS, is a greenish grey stone, unctuous to
the touchy and so soft when first taken from the quarry as to yield to
the pressure of the nail, yet not easily broken._
_It is found in a massive state._
In consequence of the softness and tenacity of this stone, it can be
turned upon a lathe, and otherwise cut and wrought with great ease.
Hence, in Egypt, Lombardy, Norway, and other countries where it is
found, it is formed into various kinds of culinary vessels and lamps,
which harden in drying, and are capable of withstanding the strongest
action of fire. Vessels of this description were known to the ancients;
and are particularly mentioned by Pliny, the Roman naturalist, who
speaks of some that were highly wrought being very valuable.
Potstone is used in some countries for the lining of stoves, furnaces,
and ovens; and it is so durable as to have, in some instances, stood
unimpaired for several hundred years.
On the banks of the Lake Como, there were some extensive quarries of
potstone, which had been worked from the beginning of the Christian era.
These quarries, however, fell in, on the 25th of August, 1618, and
destroyed the neighbouring town of Pleurs; which had previously obtained
by means of them an annual revenue of about sixty thousand ducats.
134. _COMMON, or VENETIAN TALC, is an earthy stone, capable of being
divided into plates or leaves, which are soft and unctuous to the touch,
somewhat transparent, and usually of greenish silvery white colour._
_It leaves a white trace when rubbed upon any object._
_Mica and talc have a near resemblance to each other; but the plates of
the former, when bent, are elastic, while those of the latter are not._
Venetian talc is very abundant in the Tyrol and the Valteline. In a
state of powder it renders the skin soft and shining; a property which
appears to have suggested the idea of employing it as the basis of the
cosmetic named _rouge_. This is prepared by rubbing together, in a warm
mortar, certain proportions of carmine, or extract of the flowers of
_carthamus tinctorius_, with finely powdered talc, and a certain portion
of oil of benzoin.
The Romans prepared a beautiful blue or purple colour, by combining
pounded talc with the colouring fluid of some particular kinds of
testaceous animals, that are found among the submarine rocks of the
coasts of the Mediterranean. According to Tavernier, the French
traveller, the Persians whiten the walls of their houses and gardens
with lime, and then powder them with a silvery white kind of talc;
which, he says, gives to them a very beautiful appearance. Talc is now
used by the Chinese, and was formerly used by the Europeans, in
medicine,
135. _INDURATED TALC, or FRENCH CHALK, is a heavy mineral, of close
texture, and generally of greenish grey colour; unctuous to the touch,
and having a somewhat slaty fracture._
_It is found in a massive state; and leaves a white trace when rubbed
upon any object._
This is a well known substance, which is in great request by carpenters,
tailors, hat─makers, and others, as the lines that are drawn with it are
not so easily effaced as those that are made with chalk, and
particularly as they remain unaltered even under water. If lines be
traced with it on glass, they remain invisible, or at least are scarcely
perceptible by the naked eye, till breathed upon. This, it has been
conjectured, in part depends on the comparative softness of the
substance with which the impression is made; the condensation of the
breath taking place more readily on the glass than on the talc that
covers it, and the impression of the talc becoming more apparent by the
contrast.
Indurated talc, when reduced to powder, is frequently employed for the
purpose of removing stains, occasioned by grease, from silk and cloth.
This it does effectually, and, in general, without injuring even the
most delicate colour. Like potstone, it is sometimes manufactured into
culinary vessels.
This mineral is found in several parts of the continent of Europe; and
in Cornwall, Scotland, and the Shetland Islands.
136. _ASBESTOS is a greenish or silvery white mineral, of fibrous
texture, which is found in many mountainous countries of the Continent,
in the island of Anglesea, and in Scotland. It occurs in shapeless
masses, and varies much both in weight and hardness._
The name of asbestos is derived from the Greek language, and signifies
that which is inconsumable. This mineral, and particularly a silky
variety of it, in long slender filaments, called _amianthus_, was well
known to the ancients. They made it into an incombustible kind of cloth,
in which they burned the bodies of their dead, and, by which means, they
were enabled to collect and preserve the ashes without mixture. In the
manufacture of this article they were not able to weave the asbestos
alone; but, in the loom, were obliged to join with it linen or woollen
threads, which were afterwards burned away.
Incombustible cloth was purchased by the Romans at an enormous expense.
Sir J. E. Smith, when at Rome, saw a winding sheet of amianthus in the
Museum of the Vatican. It was coarsely spun, but as soft and pliant as
silk. The person who attended him set fire to one corner of it; and the
same part burned repeatedly with great rapidity and brightness, without
being at all injured. This interesting relic was discovered, in the year
1702, in a funeral urn, and contained burned bones, together with a
quantity of ashes. It was nine Roman palms long, and about seven in
width, and had been deposited in the library of the Vatican by order of
Pope Clement the Eleventh.
Cloth made of amianthus, when greased, or otherwise contaminated with
dirt, may be cleansed by throwing it into a bright fire. In this process
the stains are burned out, and the cloth is restored to a dazzling white
colour. Pliny, the Roman naturalist, informs us that he had himself seen
table─cloths, towels, and napkins of amianthus taken from the table of a
great feast, thrown into the fire, and burned before the company: and by
this operation, he says, they became better cleansed than if they had
been washed.
The inhabitants of some parts of Siberia manufacture gloves, caps, and
purses of amianthus; and in the Pyrenees it is wrought into girdles,
ribbons, and other articles. The finest girdles are made by weaving the
most beautiful and silky filaments with silver wire. These are much
prized by the women, not only on account of their beauty, but from
certain mysterious properties they are supposed to possess.
The shorter fibres of amianthus have sometimes been manufactured into
paper, but this is too hard for use. It has, indeed, been proposed to
preserve valuable documents from fire, by writing them on paper made of
amianthus. Such a plan might deserve consideration, if we possessed
fire─proof ink; but until this be obtained, the fire─proof paper will be
of little use.
When several of the long fibres of this mineral are placed together,
they may be formed into wicks for lamps; and it has been asserted that
such wicks are incombustible. Kircher, the German philosopher, had a
wick made of amianthus which burned for two years without injury, and
was at last destroyed by accident. It is said that the inhabitants of
Greenland make use of amianthus for the wicks of their lamps.
This substance, although it will long continue unaltered in considerable
heat, yet if the heat be much increased it ceases to withstand it, and
is melted into a dense kind of scoria. In the island of Corsica asbestos
is advantageously employed in the manufacture of pottery. Being reduced
into fine filaments, it is kneaded with clay; and vessels made of this
mixture are said to be lighter, less brittle, and more capable of
sustaining sudden alterations of heat and cold than common earthenware.
CHRYSOLITE FAMILY.
137. _CHRYSOLITE, or PERIDOT, is a soft gem, usually of yellowish green
colour, though sometimes it is grass─green, or bluish green, but with a
tinge of brown._
_It is generally found in fragments and rounded pieces, and rarely
crystallized. In the latter case its regular form is an eight, ten, or
twelve─sided prism._
Though scarcely harder than glass, and consequently inferior to most
other gems in lustre, these stones are not unfrequently used in
jewellery, particularly for necklaces and ornaments for the hair; and,
when well matched in colour, and properly polished, their effect is very
good. They are, however, too soft for ring stones; for, by wearing, they
soon become dull on the surface. But it is said that their lustre may,
in some degree, be restored by immersing them in olive oil.
To give the greatest brilliancy to this stone, we are informed by Mr.
Mawe, that a copper wheel is used, on which a little sulphuric acid, or
spirit of vitriol (24), is dropped; and that, during the process, an
highly suffocating odour is given out. But he is of opinion that the
most advantageous way of working it would be that in which glass is cut.
Chrysolite is imported from the Levant, and is said to be found in Upper
Egypt, and on the shores of the Red Sea.
BASALT FAMILY.
138. _BASALT is a greyish black and coarse grained stone, which is
usually found either in globular distinct pieces or in groups of large
columns, each of which has from three to eight sides, and is divided
horizontally into numerous stones, that very exactly lie upon, or fit
into each other._
The most remarkable assemblages of basaltic columns that are known are
those called the _Giants’ Causeway_, on the coast of Antrim, in Ireland,
and the _Cave of Fingal_, in the island of Staffa, one of the Hebrides,
or Western Islands of Scotland.
The former, which is believed by the common people to have been an
artificial production, the vast labour of giants who formerly inhabited
the country, consists of an irregular group of many thousand jointed
pillars. Most of these are of considerable height; are in general
five─sided, fifteen or sixteen inches in diameter, and each perfectly
distinct from top to bottom, though so closely and compactly arranged
that it is scarcely possible to introduce any thing betwixt them. This
assemblage of columns extends into the sea to a distance unknown, and
along a tract of the sea coast of nearly six miles.
The Cave of Fingal is accessible only by sea, and is formed by ranges of
massive basaltic columns, fifty feet and upwards in height. The stone of
which these columns are formed very much resembles that of the Giants’
Causeway.
In several parts of the world large masses of basalt are discovered,
composing entire insulated mountains, of somewhat conical form. They are
considered by some writers as volcanic productions, but the proofs of
this are by no means satisfactory.
Amongst the uses to which basalt has been applied, two of the most
important are as materials of an excellent and durable kind for building
and paving. When burned and pulverized, these stones impart to mortar
with which they are mixed the property of hardening under water. They
easily melt, without any addition, into an opaque and black glass; and
from them, under a certain modification, bottles of olive─green colour,
and of extreme lightness, but great strength and solidity, have been
formed. Some of the kinds have been advantageously employed as
millstones. Basalt is occasionally used by artists for touch or
teststones, to ascertain the purity of gold and silver; and goldbeaters
and bookbinders, on the Continent, usually make their anvils or beating
blocks of it.
Basalt, though harder, more brittle, and less pleasing in its colours
than marble, was in considerable esteem among the sculptors of
antiquity, on account of its great durability. Many fine works were
consequently executed by them in this stone. Pliny, who has described
several, states that the columns of it were sometimes so large as to
admit of several figures being wrought out of them. The Emperor
Vespasian had an entire statue, accompanied by the figures of sixteen
children, cut out of a single column of basalt; this statue he placed in
the Temple of Peace, and dedicated it to the Nile. The famous statue of
Minerva, at Thebes, is described by travellers to have been formed of
basalt. Antiques of basalt are always in a much better state of
preservation than those of marble. Even such as are dug out of the earth
still retain their original polish; and the finest touches of the chisel
upon them are still unimpaired.
────────────────────────────────────────────────────────────────────────
───────
ORDER III.—SALINE STONES.
───────
LIME, OR CALCAREOUS FAMILY.
139. Lime, after it has been freed from extraneous matters by burning,
is a mineral of whitish colour, and pungent, acrid, and caustic taste.
It has the property of changing vegetable blue colours to green, and of
corroding and destroying animal substances.
This mineral is found in nearly every country of the globe: but, in a
native state, has not hitherto been discovered except in combination
with some acid.[3] The process of purifying lime, or depriving it of the
acid with which it is combined, is by burning. This is done in a large
kind of furnace, called a _kiln_, where the limestone and fuel are
heaped in alternate layers. After it has gone through this process it is
called _quick─lime_, and has the above─mentioned appearance and
qualities.
Footnote 3:
With _carbonic acid_ (26) it forms common limestone, marble, chalk,
and some other substances; with _sulphuric acid_ (24) it constitutes
alabaster, or gypsum; and with _fluoric acid_ (27) it becomes that
beautiful production, the Derbyshire spar.—All these, having lime for
their bases, are denominated CALCAREOUS SUBSTANCES.
The uses of lime are numerous and important. The principal of these is
in the formation of _mortar_, or cement for buildings. For this purpose
it is first _slaked_, by having water poured upon it: a violent heat is
thereby excited, and the lime falls into powder: it is then formed into
paste by working it with water and sand. This, when dry, becomes
extremely solid, hard, and durable. Various examples might be mentioned
of buildings nearly two thousand years old, where the lime is, at this
day, as hard as the stones which it cements together. Lime is also used
for agricultural purposes: when spread upon land it is supposed to
hasten the dissolution and putrefaction of all kinds of animal and
vegetable substances, and to impart to it a power of retaining the
moisture which is necessary for the vigorous growth of corn or grass. It
is employed in the refining of sugar, in the manufacture of soap, in the
melting of iron, and by tanners, in a state of solution, for dissolving
the gelatinous parts of skins, and removing the hair from them. The
manufacturers of glue mix it with that article, for the purpose of
adding to its strength, and preventing its becoming flexible by the
absorption of moisture. This mineral, if well dried, pounded, and
mingled with gunpowder, in the proportion of one pound to two, is of
great utility in the rending of stones and rocks: the mixture, it is
said, will cause an explosion equal in force to three pounds’ weight of
gunpowder. Lime, if swallowed or inhaled, is a virulent poison. Hence
persons employed in lime─works are subject to very distressing
complaints; and hence, if bread be adulterated with lime, it is
extremely injurious. Notwithstanding this pernicious quality, lime is of
considerable use in medicine. It is chiefly given in a state of
solution, and in the proportion of half a pound of quick─lime to twelve
pints of boiling distilled water. This preparation is called _lime
water_.
The superb basin of Lampi, one of the principal reservoirs which
furnishes the canal of Languedoc with water, was, some years ago, found
to leak at the junction of the stones. The engineer who had the
direction of the works caused lime to be slacked in the water. This,
passing through the apertures betwixt the stones, formed a crust, or
very white covering, over its whole surface, of so hard and durable a
nature, that it now constitutes one solid and undivided substance, which
the water cannot penetrate.
CARBONAT OF LIME.
140. _COMMON LIME is a variety of carbonat of lime, or of lime in
combination with carbonic acid (26), which is harder and heavier than
chalk, usually of a greyish colour, and is always found in a massive
state._
Vast mountains of limestone occur in several countries of the globe; but
no where is lime more abundant than in some parts of England and Wales.
It forms, in particular, nearly the whole mountainous districts of
Derbyshire and Shropshire, and encloses, in its substance, numerous
veins of lead ore, calamine, and other important mineral productions.
Its uses have been already described (139).
141. _CHALK is a white or yellowish kind of limestone, too well known to
need any description._
It is found abundantly in many of the southern counties of England, and
is usually procured from large open places, called chalk─pits, by
digging. In some parts of Kent, however, the workmen save themselves, in
this respect, much trouble. They undermine the sides of hills to a
certain depth, then dig a trench at the top as far distant from the edge
as the mining extends at the bottom. This trench they fill with water,
which soaks through during the night, and the whole mass is thereby
loosened, and falls down before morning.
The harder and more compact kinds of chalk are cut into blocks, and used
as building stones. When burned and formed into lime, chalk becomes an
excellent mortar: nearly all the houses in London are cemented with
chalk mortar. It is also used as lime in agriculture. As it readily
imbibes water, it is used by starch─makers, chemists, and others, to dry
precipitates upon. With isinglass or the white of eggs it forms a
valuable lute or cement. By artists it is in request for the
construction of moulds to cast metals in; and by carpenters and others,
as a material to mark with. Chalk is one of the most useful absorbents
that are employed in medicine: it likewise gives name to an officinal
mixture, to a powder, and a potion.
When pounded and cleared from gritty particles, it has the name of
_whiting_. In this state it is used for the cleaning and polishing of
metallic and glass utensils; for whitening the ceilings of rooms, and
numerous other purposes. _Spanish white_ is the same substance cleansed
with peculiar care; and the _Vienna white_, which is used by artists, is
perfectly purified chalk.
142. _MARBLE is a compact and close─grained kind of limestone; so hard
as to admit of being polished. It is this quality which principally
distinguishes it from other calcareous substances._
Although nearly all the numerous kinds of marble may be burned, and thus
converted into quick─lime, their use in ornamental architecture, &c. is
so important as, in general, to prevent their application to the
inferior purpose of mortar. Marble has been known from a very early
period. The Book of Esther, in the Old Testament, describes the palace
of Ahasuerus to have had “pillars of marble,” and the pavement of “red,
and blue, and white, and black marble.”
It would be impossible, in an elementary work like the present, to
describe, or even to enumerate, all the different kinds of marble which
were known to the ancients, or are known to the moderns. But it is,
perhaps, requisite that an account should be given of some of the most
important of them.
_GREEK MARBLES._—143. PENTELIC MARBLE _is of beautiful white colour, and
nearly resembles the Parian marble_ (145) of the Italians; but it is in
coarser granulations. Sometimes it is splintery. It was obtained from
quarries on Mount Pentelicus, near Athens, and was generally preferred,
by the Grecian artists, to Parian marble. The Pantheon was built
entirely of Pentelic marble; and many of the Athenian statues, and works
carried on near Athens during the administration of Pericles, were
executed in it. Dr. Clarke, however, has observed that while the works
wrought of Parian marble remain perfect to the present time, those of
Pentelic marble have been decomposed by the atmosphere, and sometimes
exhibit a surface as rude and earthy as common lime─stone. There are
numerous examples of Pentelic marble in those works of Phidias which
form the Elgin collection in the British Museum.