colonnade of Ingrian granite. The columns are sixty in number, and each
of a single piece twenty feet high, and three feet in diameter. Many of
the public buildings in Petersburg are of this granite. An immense block
of it thirty─two feet long, twenty─one feet broad, and seventeen feet
high, forms the pedestal of the celebrated equestrian statue of Peter
the Great, in that city.
254. GRAPHIC GRANITE.—A singular kind of granite has been discovered in
the island of Corsica, and lately near Portsoy in the north of Scotland.
The ground of this granite is a whitish or reddish yellow felspar, in
which are embedded crystals of quartz each from an inch to an inch and
half long, and several lines in diameter. The name of graphic granite
was given to it in consequence of an imaginary resemblance which the
sections of these crystals have to Hebrew, or Arabic, and sometimes to
musical characters.
255. _GNEISS is a primitive rock, consisting, like granite, of felspar
(110), quartz (76), and mica (123), but differing from that rock in its
structure, being slaty._
Mountains of gneiss are not so steep as those of granite, and their
summits are usually rounded. Ben Lomond and others in Scotland, and
mount Rosa in Italy, are almost wholly of gneiss, as well as the middle
part of the Pyrenees. It is not an uncommon rock, but in Britain is of
less frequent occurrence than granite.
Many valuable metallic ores are found in veins of gneiss. This rock also
sometimes contains crystals of garnet (70), and tourmaline (69).
256. _MICA SLATE, or MICACEOUS SCHISTUS, is a primitive rock of slaty
structure, consisting principally of quartz (76) and mica (123)._
Like gneiss, it is rich in ores. It often contains beds of magnetic
ironstone (235), galena (239), copper, blende (241), cinnabar (228), and
sometimes even gold. It frequently has garnets, and sometimes
tourmalines (69), interspersed in different parts of it.
Mica slate occurs in many parts of Scotland; the mountain of
Schehallien, and the rocky adjacent country, are in a great degree
composed of it.
257. _CLAY SLATE is a primitive rock generally of dull blue colour, more
or less compact, always slaty, and always stratified._
Under the appellation of clay slate are included _roofing slate_ (120),
_whet slate_ (122), _drawing slate_ (121), and some other kinds already
described.
Few rocks abound more in veins and beds of valuable metals than slate.
In different countries it contains ores of tin, lead, cobalt (247),
silver, and copper; and gold, and mercury (228) sometimes occur in it.
The celebrated quicksilver mines of Idria (228), and the immense mass of
copper at Parys mountain in the island of Anglesea (230), are in clay
slate. Crystals of pyrites (236), and sometimes garnets (70), and thin
layers of quartz (76), and felspar (110), are all occasionally found
embedded in it.
This is a widely─extended rock; it sometimes forms whole mountains, and
even chains of mountains; but these usually have a gentle acclivity. The
summit of the celebrated mountain called Skiddaw in Cumberland is of
clay slate.
258. _PRIMITIVE LIMESTONE is a simple mountain rock of crystalline or
granular structure; and generally of white, yellowish, greenish, or
reddish colour._
To this species of rock belong many of the rich and beautiful kinds of
marble already described (143, &c.). Carrara, or statuary marble (146),
is a familiar instance of it. Whole mountains in Stiria, Carinthia,
Carniola, and the Pyrenees, and three mountains in Switzerland, 10,000
feet in height, are of primitive limestone. The mountain of Filabres in
Spain, is said to consist of one block of white granular marble, 2,000
feet high, and three miles in circuit; without intermixture of other
earths or stones, and almost without a fissure.
Various mineral ores, in beds and veins, as lead, zinc (241), and iron,
are occasionally found in this kind of rock.
259. _PRIMITIVE TRAP is a mountain rock composed of a black mineral
called hornblende, mixed, in some varieties, with felspar (110), and, in
others, with mica (123)._
The word _trap_ is of German origin, signifying a _stair_; and rocks of
this formation are called trap rocks, because their strata, when
exposed, usually jut out, one beneath the other, somewhat like a stair.
Under this term is comprehended a series of rocks, distinguished chiefly
by the hornblende, which they all contain.
Rocks belonging to this formation are numerous. They occur in Scotland;
and abundantly in Derbyshire and some other parts of England. In many
countries they constitute considerable hills. They abound in ores.
260. _SERPENTINE is a primitive rock, usually consisting of quartz (76),
magnesia (198), alumine (197), with a portion of oxide (21) of iron._
This rock and its various uses, have been already described (132). It
generally occurs in shapeless masses and beds; and seldom in distinct
strata. It is found in Cornwall, the island of Anglesea, and several
parts of Scotland; but it rarely forms mountains.
Ores of lead, silver, and copper, are sometimes found in serpentine.
261. _PORPHYRY is a primitive rock, consisting of quartz (76) or felspar
(110), or both, embedded in a solid and compact cement or ground._
_The ground or basis of porphyry varies in the different kinds. In some
it is claystone, in others pitchstone, hornstone, or compact felspar._
When not covered by other formations, porphyry sometimes forms single
rocks; but it never constitutes elevated mountains. It occurs in beds of
considerable magnitude, but never appears in distinct and well─defined
strata.
There are many beautiful and splendid works in porphyry. Obelisks,
statues, and columns, wrought in it, have had great celebrity. It is
susceptible of a polish as high as that of marble, but is so hard, that
the expense of working it has caused it to be much neglected by the
moderns. This hardness, however, renders it very durable, and also
constitutes it a material of great utility for mortars, slabs for
grinding colours upon, and for several other purposes.
Porphyry was much esteemed by the ancient Egyptians; and Pliny informs
us that the procurator─general in Egypt, under Claudius Cæsar, brought
thence, for that Emperor, certain statues of porphyry, which he
conceived to be very valuable: this act, however, was not much approved,
and the example was not followed by any other Roman.
The principal quarries of porphyry are in Egypt; but this stone is also
found in Italy, Germany, and various parts of the European continent. It
may be traced from Norway to the borders of the Black Sea, and it has
been discovered in some of the western and northern parts of Great
Britain.
262. _SIENITE is a rock composed chiefly of felspar (110) and
hornblende. Its colours are usually reddish and black._
_Some varieties of it contain quartz (76) and mica (123), with but
little hornblende. In these the colours are various._
Although this is a less abundant rock than any of those that have yet
been mentioned, it occurs, in great abundance, at Mount Mado, in the
island of Jersey. There are extensive quarries of it in that mountain,
not only for the use of the island, but for exportation to England, and
other distant countries. The cliffs, for a long space, and an elevation
of a hundred feet or more, consist entirely of sienite, in large masses,
which are apparently uninterrupted by a single fissure. Shafts for
columns of considerable length have been taken from these quarries; and,
were the demand sufficient to call for new openings, it is imagined that
columns of twenty feet and upwards in length might be raised. The
felspar is of a flesh colour, and the stone is capable of a beautiful
polish.
A somewhat similar kind of sienite is found at Grande Roque, in the
island of Guernsey, in large masses, which are quarried for building
stones. Sienite also occurs in some parts of Scotland and Derbyshire; in
Saxony, Hungary, the island of Cyprus, and Egypt. Its name has been
derived from that of the city of Syene, in Upper Egypt, where it is
found in great abundance.
Sienite was much used by the ancients in ornamental architecture. What
was called the red granite of Egypt (for this rock has usually been
considered a granite) furnished numerous magnificent obelisks and
columns, of a single piece, which have been much admired in Rome and
other places. The ancient artists sometimes cut this kind of stone into
statues, vases, monumental and other works. The celebrated column in
Egypt, upwards of ninety feet high, and known by the name of Pompey’s
Pillar, is formed of sienite.
In veins of this rock are found, in different countries, many kinds of
metallic ores: among others, silver, iron, tin, copper, and lead.
263. _QUARTZ ROCK is a simple mountain rock, usually of granular
texture, and whitish colour._
_It sometimes contains mica, in which case it has a slaty form._
In certain mountains of Scotland, and the Scottish islands, quartz rock
is very abundant. On the Continent it appears in Saxony, Bohemia,
Silesia, and several other countries. We are informed that a mountain,
350 feet high, and near 5000 feet broad and long, one of the Altaisch
chain, in Siberia, consists entirely of a milk─white quartz.
The uses of quartz have been already described (76, &c.) This kind of
rock does not contain metallic ores of any description.
II. SECONDARY ROCKS.
264. SECONDARY ROCKS _are composed of, or at least contain within them,
the mineralized remains of organic substances_. These must necessarily
have been formed at a period subsequent to the formation of those
organized bodies the remains of which they enclose; and they have
apparently been formed by the deposition of water. Hence it is that, to
distinguish them from rocks of the preceding class, they have received
the appellation of secondary. They always rest upon or cover primitive
mountains, and sometimes lean upon their sides or invest them.
Werner, the celebrated German mineralogist, makes two divisions of
secondary rocks. The first of these he denominates _transition rocks_,
and states that they are less perfectly crystallized than the primitive
rocks; and that they enclose the remains of marine animals, no species
of which are at this time known to exist: the other division he terms
_floetz_, or _flat rocks_, because they are generally disposed in
horizontal or flat strata. Some of the latter contain the fossil remains
of marine animals and shells, approaching in character and appearance to
the kinds which are now found in the ocean; and others contain shells
precisely similar to those now known to exist. These rocks usually occur
at the foot of primitive mountains, or in deep valleys.
1. TRANSITION ROCKS.
265. _TRANSITION LIMESTONE is distinguished by containing marine
petrifactions of corals, and other zoophytes which are supposed no
longer to exist. It often contains veins of calcareous spar, and
exhibits a variety of colours, which give to it a marbled appearance._
This species of limestone occurs in immense beds, and forms a great
portion of the mountainous parts of Derbyshire and Scotland; but it does
not rise so high, on the sides of mountains, as primitive rocks (250).
It often contains veins of valuable metallic ores. When cut and
polished, many of the varieties of transition limestone are beautiful
marbles; some of them have been already described.
266. _GREY WACKA is a transition rock, composed of pieces of quartz
(76), flinty slate, felspar (110), and clay slate (120), cemented
together by a basis of clay slate._
_It has various appearances, the pieces being sometimes as large as a
hen’s egg, and sometimes so small that they can scarcely be perceived by
the naked eye._
When the rocks of grey wacka are not covered by those of any other
formation, they form round─backed hills, usually insulated towards the
tops, and intersected by deep valleys. They are widely distributed: and
are often extremely rich in ores, both in beds and veins. Almost all the
mines of copper, lead, and zinc, in the Hartz, are in grey wacka; and,
in Transylvania, this species of rock is traversed by numerous small
veins of gold.
2. FLOETZ, OR FLAT ROCKS.
267. _OLD RED SANDSTONE, or MILLSTONE GRIT, is a floetz or flat rock,
composed of large grains of sand or quartz (76), coloured by oxide (21)
of iron, and usually cemented together by a kind of clay._
In several parts of Derbyshire this kind of rock forms the uppermost
stratum; and in some places, is known to be 120 yards thick.
What are known by the name of _peak millstones_ are formed of millstone
grit. They are chiefly obtained from quarries near Nether Padley, in
Hathersede, Derbyshire; a very inaccessible part of the country, but
where the stone is of better quality than it can elsewhere be procured.
These millstones are made of different dimensions, from two feet in
diameter, and eight inches thick, to five feet and half in diameter, and
seventeen inches thick.
Some of the beds of millstone grit, which have spherical stains in them,
of light red colour, are said to be infusible; and are consequently a
valuable stone for lining the hearths of iron and other furnaces, where
an intense heat is required. These are called _firestones_, and Roches
quarry, near Upper Town, in Ashover, Derbyshire, is famous for them.
The upper beds of this kind of rock are often thin, and capable of
division, so as to make excellent _paving stones_, or _flags_. There is
a particular bed of it at Stanton, in the Peak of Derbyshire, so porous
that it is made into _filtering stones_ for the cleansing of turbid
water.
268. _THIRD SANDSTONE, GRITSTONE, or FREESTONE, is another kind of
floetz or flat rock, formed of very small agglutinated particles of
sand. It is opaque, usually of whitish colour, and found in large
masses, of various degrees of hardness._
The name of _freestone_ has been given to this kind of rock, from its
capability of being broken or hewn, with nearly equal facility, in any
direction. Hence, as well as from its great durability, it is peculiarly
esteemed for buildings. It is also formed into cisterns and troughs of
various kinds; into pillars for supporting corn ricks; into _rolling
stones_; and into _grinding stones_ for cutlers, edge─tool makers, and
workers in polished steel. _Paviors’ flags_, or the stones used for the
paving of footpaths, yards, kitchens, and out─houses, are generally flat
pieces of freestone.
_Scythestones_, or stones for the sharpening of scythes upon, are made
of freestone. Considerable numbers of these are wrought in Derbyshire;
and the dexterity that is displayed in cleaving and forming them is
somewhat remarkable. The workmen use sharp─pointed picks, several very
small wedges, and a hammer. A proper block of stone being selected, two
or three of these small wedges are set in a row, by gentle blows of the
hammer. These blows are successively repeated till the stone splits. The
wedges are then set in a straight line into the face of the piece split
off, and the stone is cleft again in that direction. In this manner the
sub─divisions are continued, until a piece remains of size to make two
scythestones, each an inch and a half square, and about twelve inches
long. This the workman holds in his left hand, nearly upright; with the
point of his pick he traces a deep nick down the middle of first one
side and then the other; and then by a slight blow of his pick he
separates it, into two, so dexterously, that not more than three or four
in a hundred are broken in the cleaving. Such stones as are intended for
round rubbers, are first reduced into an octagonal shape by the point of
the pick, and then handed over to women and boys, who grind or rub them
in a notch formed in a hard stone, until they are of the requisite
shape. The square ones are finished by being ground on a flat stone.
* * * * *
Other rocks, belonging to what is called the floetz, or flat formation,
have been already mentioned, under the heads of _lime─stone_ (140),
_gypsum_ (192), _rock salt_ (202), _chalk_ (141), and _coal_ (217).
III. ALLUVIAL DEPOSITIONS.
269. _These are described to comprehend all such substances as have been
formed from previously existing rocks, of which the materials have been
worn down, by long exposure to the agency of water and air, and
afterwards deposited in nearly horizontal beds on the surface of the
land._ Alluvial deposits have been formed, and are still forming in
every quarter of the globe. They occur both in mountainous regions and
in flat countries, filling up the valleys or hollows in the one; and
often forming vast and extended plains in the other.
They consist of _peat_, _sand_, _gravel_, _loam_, _clay_, and other
substances.
IV. VOLCANIC ROCKS.
270. _Volcanic rocks are composed of such mineral substances as have
been ejected from volcanoes, or have been formed by the agency of
subterraneous fires, and have undergone certain changes in such fires._
They are of two kinds; the one called _pseudo volcanic_, such as burnt
clay, porcelain jasper, and earth─slag, which have been altered in
consequence of the burning of beds of coal in their neighbourhood; and
the other, called _true volcanic_ minerals, such as stones, ashes, and
lava, which have been thrown out of real volcanoes.
271. It will somewhat tend to illustrate the history of the mineral
kingdom, to state, in conclusion, under a tabular form, the relative
heights of the principal mountains, or masses of rocks, which occur in
the different countries of the world; previously remarking, that the
most lofty and magnificent of these, respecting which any account
sufficiently authentic has hitherto been obtained, are the mountains of
Nepaul and Thibet, in Asia, one of the former being 27,667, and the
highest of the latter measuring at least 23,262 feet, or from 4½ miles
to 5¼ miles in perpendicular height above the level of the sea.
Previously to the knowledge that has lately been attained respecting the
Asiatic mountains, those of the Andes, on the continent of South
America, had been considered by far the highest in the world. One of
them, Chimborazo, is 20,900 feet in height. Of the European mountains,
the highest is Mont Blanc, in Switzerland, which measures 15,680 feet,
or about 2¾ miles. The loftiest summit within the British islands is Ben
Nevis, in Inverness─shire, Scotland, which does not exceed 4,380 feet,
or somewhat more than three quarters of a mile; and the great pyramid of
Egypt, the loftiest work of human art and industry with which we are
acquainted, and which will serve as a point in the scale, measures only
477 feet.
272. It has been remarked that the greatest altitude at which _bananas_
and other _palm─trees_ grow in America is about 3280 feet above the
level of the sea (Frontispiece, Fig. 48): that in the torrid zone, the
superior limits of _oaks_ is about 10,500 feet (49), of _pines_ 12,000
feet (50), and of _lichen plants_ 18,225 feet (51). The American
travellers, Messrs. Humboldt and Bonpland, on the twenty─third of June,
1802, ascended the mountain of Chimborazo to the height of 19,400 feet
(52). The highest flight that has been remarked of the South American
vulture, called the _condor_, was 21,000 feet (53). M. Lussac, on the
16th of September, 1804, ascended in a balloon from Paris, to the height
of 22,900 feet. In Switzerland, the limit of perpetual snow is above the
altitude of 9000 feet (54).
=Height of the Principle Mountains.=
_Frontispiece._
Ft.
above
Fig. the sea
=_British Islands._=
Scotland Ben Nevis, Inverness─shire 1 4380
Ben Lawers, Perthshire 2 4051
England Skiddaw, Cumberland 3 3530
Cross Fell, Cumberland 4 3390
Helvellyn, Cumberland 5 3324
Wharnside, Yorkshire 6 2480
Ingleborough, Yorkshire 7 2380
Wales Snowdon, Caernarvonshire 8 3568
Cader Idris, Merionethshire 9 3550
Ireland Macgillicuddy’s Reeks, Kerry 10 3404
Sleibh─Dorin, Londonderry 11 3150
=_Continent of Europe._=
France Mont d’Or, Auvergne 12 6707
Puy de Sausi, Auvergne 13 6700
Pyrenees Mont Perdu, the highest of the 14 11,283
Pyrenees
Le Pic Blanc, Spain 15 10,205
Alps Loucira 16 14,451
Loupilon 17 14,144
Switzerland Mont Blanc, highest mountain 18 15,680
in Europe
Mont Rosa 19 15,555
Mont St. Gothard 20 10,014
Italy Mont Cimone 21 6401
Vesuvius 22 3900
Germany Ortler─Spitze, Tyrol 23 15,430
Ostelle, Saltzburg 24 12,800
Carpathian Mountains, highest 25 8640
summit
Lomnitz Peak 26 8640
Sweden Areskutan, Jempland 27 6180
=_Islands._=
Teneriffe Peak of Teneriffe 28 12,236
Sicily Ætna 29 10,963
Jamaica Blue Mountains 30 7431
Iceland Snæfiel 31 6860
Hecla 32 4900
=_Asia._=
India Dhawalgeri in Nepaul 46 27,667
Mountains of Thibet 47 23,262
Turkey Mount Lebanon, estimated at 33 9520
in Asia Mount Ararat, estimated at 34 9500
Mount Ida 35 4960
=_America._=
Andes, South Chimborazo, Quito 36 20,900
America. Cotopaxi, Quito 37 18,880
=Height of Remarkable Lakes, Cities, &c.=
Alps Lake of Lausanne 38 8640
Lake of Lanzon, on the 39 6797
mountain of Olan
Switzerland Lake of Lucerne 40 1408
South America City of Riobamba, Quito 41 18,800
City of Quito 42 9356
North America City of Mexico 43 7424
Austria Town of Eisenerz 44 2056
Egypt The great Pyramid 45 477
────────────────────────────────────────────────────────────────────────
WATER IN GENERAL.
───────
273. WATER, generally speaking, is a transparent and nearly
incompressible fluid, the component parts of which are two kinds of gas,
called hydrogen (45) and oxygen (21).
It is _liquid_ in the common temperature of our atmosphere, assumes a
solid state under the denomination of _ice_, in a cold temperature (32°
of Fahrenheit’s thermometer); and, by heat at 212°, is converted into an
elastic vapour of almost incredible force, called _steam_. At any
temperature betwixt these two points, it returns, unaltered, to its
liquid state. The weight of water is about 816 times greater than that
of atmospheric air.
Water abounds in, and may be considered as, a kind of general cement to
all solid bodies. It performs the most important functions both in the
animal and vegetable kingdoms, and even enters largely into their
composition.
A chief part of the nutrition of vegetables is the water which they
absorb from the earth through the pores of their roots. The great
quantity so absorbed may readily be imagined, when it is stated that the
driest and most compact kinds of wood, such as even heart of oak, when
converted into charcoal, lose, during the process, full three─fourths of
their weight; and that the fluid which escapes is nearly pure water.
This fluid is found in the driest of solid bodies, whatever be their
description. A piece of hartshorn kept for forty years, and thereby
become as hard and dry as metal (so that if struck against a flint it
would give sparks of fire), upon being distilled, was found to yield an
eighth part of its weight of water.
Every being with life, in a great degree, lives by it; and whatever
grows, through it receives its growth; and wherever it enters, it
promotes and sustains life, preserving the whole of created nature in
their proper classes of existence. And whether we consider it as
productive of health to animals and vegetables, as requisite to the
existence and beauty of the earth, or as one of the great powers by
which the Almighty works in the support of the world, we cannot but
admire and adore the wisdom by which it has been ordained.
In the various kinds of water, even of that which is commonly used in
drinking, and for the preparation of food, there is great difference
both of taste and appearance. This difference is chiefly occasioned by
the foreign matters which they hold in solution or suspension. In some
cases the quantity of these is so minute as to have but little influence
on the taste; but in others they alter its properties altogether, and
render the water noxious, or medicinal, or unfit for the preparation of
food.