Part 20

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

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WATER IN GENERAL.

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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.

The _chemical analysis of water_, for the purpose of ascertaining the different substances which it holds in solution, is one of the most difficult and complicated operations that is known in this branch of science; and one that exercises, in a peculiar degree, both the skill and industry of the operator. The difficulty arises not only from the diversity of the bodies which occur, but from the very minute quantities of some of them.

These bodies are discovered by an addition to the water of certain substances, the consequence of which is some change in its appearance, and this change indicates the presence or absence of the bodies suspected.

The substances thus employed are very numerous, and have the name of _tests_. The methods of ascertaining the exact proportion of each of these ingredients are much too complicated to require a place in the present work.

Water cannot be obtained in any state of perfect purity except by the artificial process of distillation.

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ORDER I.—COMMON WATER.

274. _RAIN WATER is considered to be next in purity to distilled water, from its having undergone a natural distillation. Its foreign contents vary according to the state of the air through which it falls. Hence, for instance, when it passes through the atmosphere of a smoky town, it becomes impure: and when collected in towns, it frequently acquires a small quantity of sulphat of lime (192), and calcareous matter from the mortar and plaster of the houses._

This water is always very soft; and is, consequently, well calculated for the dissolving of soap, in washing and other processes. It is also peculiarly adapted to the solution of alimentary or colouring matter, in the preparation of food and dyeing, and is accordingly used to great extent for these purposes. By the addition of a small quantity of a solution of barytes (195), it may be rendered sufficiently pure for all chemical uses.

If rain water be long kept, especially in hot climates, it acquires a disagreeable smell, and becomes putrid, and full of animalculæ.

275. _ICE and SNOW WATER are equal to rain water in purity; and the air having been expelled from them during the process of freezing, they are consequently devoid of air when first melted._

Ice and snow, in their natural state, are highly important to mankind. It is a general law of nature that all bodies become more dense and heavy by exposure to cold; but the freezing of water is an exception to this law, and for a purpose of extreme benefit to mankind. By this ordination it is that ice always rises to the surface of the water, and thus preserves from the effects of the surrounding cold, a vast body of heat in the fluid beneath; and is itself ready to receive its own accustomed quantity upon the first change of the atmosphere. The expansion of water, in freezing, is owing to its assuming a crystallized form; and this expansion is often so great that glass bottles, filled with water, are burst by it.

During the intense cold of winter, snow, which is of a soft and spongy texture, is considered of great utility in preventing the immediate access of the atmospheric air to the ground; it has doubtless been designed by Providence as a garment to protect the incipient vegetation, at that inclement season, from injury.

The inhabitants of all the extreme northern parts of the world use thawed snow for their constant beverage during winter; and the vast masses of ice which float in the polar seas afford an abundant supply of fresh water to the navigators of those dreary regions. Snow water has, however, long lain under the imputation of occasioning those extraordinary swellings in the neck, which deform the inhabitants of some of the alpine valleys of Switzerland; but this opinion is not supported by any well─authenticated facts. Indeed it is rendered quite improbable by the frequency of this disease in the island of Sumatra, where ice and snow are never seen: and by its being quite unknown in Chili and Thibet, though the rivers of these countries are chiefly supplied by the melting of the snows.

276. _SPRING WATER is nothing more than rain water, which having gradually filtered through the earth, collects at the bottom of declivities, and there makes its way to the surface._

_It is obvious that spring water must be nearly as various in its contents as the substances through which it flows._

Ordinary springs pass insensibly into mineral springs, according as their foreign contents become more abundant; but it has not unfrequently happened that waters have acquired great medical reputation from their purity only. Although by far the greater number of springs are cold, some are hot, or at least are of a temperature which, at all times, exceeds that of summer heat: and this warmth is so little influenced by the state of the atmosphere, that it is nearly the same both in summer and winter.

The water of almost every spring is of such nature that it will not dissolve, but curdles, soap; and cannot be used for dressing several kinds of food. Water of this description is denominated _hard_, a property owing to the great proportion of earthy salts which it holds in solution, and which, at the same time, are not in such abundance as to impair its taste. The most common of these salts is selenite, or sulphat of lime (192), and chalk, or carbonat of lime (140); when it contains only the latter, the water is easily rendered soft by boiling, which expels the excess of carbonic acid (26), and thus causes the chalk to be precipitated. Hence originates the earthy crust or _fur_ in such tea kettles as have had hard water several times boiled in them.

The water of deep wells is for the most part much harder than that of springs which overflow their channels.

277. _RIVER WATER is a mixture of spring and rain water, which, from much agitation, and by long exposure to the air, in the course of its channel, becomes, in general, tolerably soft and free from earthy salts._

For washing, and other purposes of domestic economy, river water, from its softness and purity, is not only preferable to spring water, but also serves for many uses to which the latter cannot be at all applied. As a beverage, however, it is in general vapid and unpleasant.

The waters of some rivers, particularly where the beds, over which they flow, are sandy or stony, are remarkably pure. This is the case with several of those in Switzerland, Wales, Scotland, and the northern counties of England. The river Seine has great repute in France on this account: it has been found, on accurate examination, even more pure than Bristol water.

That of the river Thames, impregnated as it would appear to be with putrid remains, is soft and good, when taken up at low water; and, after rest and filtration, is found to contain but a small portion of any thing either noxious or unpleasant. It is preferred, by mariners, to most other water for sea store; but it soon becomes putrid, and undergoes a remarkable spontaneous change. When, after having been kept a month or two, a cask is opened, a quantity of inflammable air escapes, and the water is black and nauseous. If, in this state, it be racked off into large earthen vessels (oil jars it is said are commonly used for the purpose), and exposed to the air, it gradually deposits a portion of black slimy mud, and becomes perfectly clear, sweet, and fit for use.

278. _STAGNANT WATER contains greater impurities than any other. In ponds and marshes particularly, it is filled with the remains of animal and vegetable matters, which are there undergoing a gradual decomposition._

_The water of lakes is not, in general, so much contaminated as this; but from the same cause, it frequently has a slimy appearance, a brownish colour, and an unpleasant taste._