CHAP. I.-MINERAL KINGDOM.

1. THE name of mineral, in the strict sense of the word,

denotes only such substances as are found in mines, but the term is generally applied, in a more extended sense, to characterize that class of inorganic and inanimate bodies, which form the solid mass, or rather, the external covering, of the globe we inhabit,-so far at least as the labour of man has hitherto penetrated. To the whole of these substances is given the appellation of MINERAL KINGDOM, in opposition to the two other grand divisions of nature of which we shall afterwards treat.

2. Minerals, like organized bodies, have a certain origin, progressively increase, and are subject to dissolution, or decomposition of parts. But they arise merely by an accumulation of homogeneous, or similar particles from without; either by substances combining in consequence of their attractive power, which is called cohesion; or by the solid particles being separated from the fluid ones, when the former attract each other, according to certain laws, constituting together a solid body; and this is termed crystallization, a form of which only certain minerals are susceptible. Mineralogy is that department of the science of nature which makes us acquainted with the characters of ninerals. It teaches the art of distinguishing them by accurate and well defined characters; the mode of describing them with so much precision, as is sufficient to recognize them with facility whenever they occur, and the art of arranging or classing them in a certain order or system.

3. The characters of minerals in their most striking properties, may be thus illustrated. (1.) Fusibility means the power of being melted. The most ready way to ascertain the fusibility of a mineral substance, is, by exposing a small particle of it to the flame of a candle or lamp concentrated by the instrument called a blow-pipe; and, if the heat thus excited is sufficient to liquefy the mineral, it is said to be fused. (2.) The hardness of minerals is ascertained either by a comparison with each other, or by their power of scratching glass, or the effect of the file upon them: those which resist the file being the

hardest. (3.) The phosphorescence of minerals means the faint light which they emit, either by exposure to simple heat, or in consequence of friction. (4.) The electricity of a mineral is that property which, being excited either by simple heat or by friction, shows itself in the attraction or repulsion of other substances, with which the mineral is brought nearly in contact. (5.) By the specific gravity of a mineral, is understood the amount of its weight, when compared with the weight of a quantity of water of the same bulk with itself. (6.) The crystalline forms under which minerals occur, are various, and may be considered as one of their most important characters, being, with some few exceptions, resolved into six principal forms.

4. Minerals are usually arranged under four classes; earthy, saline, inflammable, and metallic.

1. Earthy. This class is distinguished by its being in general brittle, not remarkably heavy, as usually possessing white or light colours, disposed to crystallizę, uninflammable in a low temperature, insipid, and inodorous. The earthy minerals are either SILICEOUS, in the form of pebbles, gravel, sand, sand-stones, puddingstones, &c.; or are CALCAREOUus, as limestone, chalk, spar-marble, alabaster, &c.; or ARGILLACEOUS, as clay, fullers' earth, lithomarga, boles, slate, &c. ; or MAGNESIAN, as steatites, asbestus, serpentines, &c.; or BARYTIC, as the baroselenite or ponderous spar, &c. In these compounds, in which more than one of the earths are found, the earth from which each substance derives its genuine distinction is most abundant, so there are also others in which the earths STRONTIA, YTTRIA, and JARGONIA are most predominant. Most of the PRECIOUS STONES are compounds, in which different combinations of one or more of the other earths, lime, alumine, magnesia, and sometimes a small portion of iron, are united to a large portion of pure quartz, or silex, in a crystalline form, hence result the opal, garnet, catseye, onyx, sardonyx, &c.

The ruby has been found to be formed of alumine and magnesia, with chromic acid, and the emerald is supposed" to be the same compound with the acid in a different degree of oxidizement. The chrysolite appears to be composed of lime and the phosphoric acid.

II. The class of saline minerals is characterized by

being moderately heavy, white, sapid, soft, and possessing some degree of transparency.

III. The characters of the inflammable class are, lightness and brittleness: the individuals in this class are mostly opaque, scarcely ever crystallized, and do not feel' cold. Here may be placed the bitumens, amber, jet, petroleum, coal, &c. In this class may also the diamond be placed.

IV. The metallic class contains many genera, characterized by opacity, and great specific gravity: they generally possess a peculiar lustre, are tough, and in some degree malleable, cold, and not easily inflamed.

Under each of these classes are various genera, species, sub-species, and kinds.*

Mineralogy is chiefly employed in arranging similar bodies under the same, and dissimilar bodies under different denominations, and it judges of them by external appearances or internal compositions. (1.) External characters are discovered by observing the figure, colour, texture, fracture, or other properties which the different bodies present to our senses, without undergoing any material alteration. (2.) Internal constitution. This knowledge is acquired chiefly by regarding the changes produced in them, by the chemical action of other bodies. this knowledge is derived the economical application of minerals in agriculture, metallurgy, and the arts.

And from

5. Analytical Mineralogy, or the analysis of minerals, is a branch of philosophical chemistry. It teaches the art of examining minerals, not by the help of external characters, but chiefly by chemical agencies. Its views are directed to the development of the constituent parts of minerals, the order in which they are present, their relative quantities, and the best modes of separating them. Mineral waters are found in those places where there is an abundance of iron, copper, sulphur, and pit-coal. Hence their taste and effects are different, in proportion as they are more or less impregnated with the above principles. They are also subject to other impregnations, and from their salubrious effects in some diseases, when containing different salts, iron, and sulphur, many of these waters have

For a brief notice of the earths, salts, metals, &c., see CHEMISTRY.

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been successfully employed in medicine, and have been termed medicinal.

6. Geology comprises the structure and formation of the globe; embracing the consideration of the materials of which it is composed, and the circumstances peculiar to its original formation, as well as the different states under which it bas existed, and the various changes which it has undergone. While difficulties which were supposed to render the Deluge impossible, have been removed by the investigations of modern geologists, many facts have been at the same time brought to light, showing the possibility, and even certainty, of that mighty inundation. In every valley and mountain, support for revelation has been found. Marine shells have been discovered in situations so elevated, and under circumstances so remarkable, as to prove that they were left there by a flood extending over the whole globe; and what confirms this conclusion is, that shells peculiar to different shores and climates very distant from each other, have been found in promiscuous heaps; plainly showing that they could have been brought toge ther only by an extensive inundation. The bones of the elephant and the rhinoceros, have been found in a multitude of instances, far distant from the regions in which they were found to live, and where from the nature of the climate they could never exist in the living state: and between the climates which they might have inhabited, and the places in which they are now found, too many mountains intervene, to suppose them carried thither by any other means than that of a general deluge.*

7. Whether we excavate the plains, penetrate into the caverns of mountains, or scale their rugged sides, every where the spoils of organized bodies are buried in those beds which form the external coat of our earth. Banks of slate contain fish, and beds of coal display impressions of vegetables, at elevations or at depths equally astonishing. Here beds of shells, extending for many miles under ground, cover others which contain only vegetables :-there the bodies of fish are placed above land animals, and they, in their turn, are covered by strata or layers, containing the remains of plants and shells. Torrents of lava, and

• Kirwan's Geological Essays, p. 54, et seq.

heaps of pumice-stone, the products of subterraneous fire mingle, in other places, with the inhabitants of the ocean.

8. The internal constitution of the earth is but little known. The deepest excavations that have been made by human art, do not exceed 2400 feet, or less than half a mile; which is a very short distance indeed when compar ed with the diameter of the earth, which is about 7947 English miles. The inside of the earth is consequently in a great measure unknown to us. The upper crust or surface is found to be composed of different strata, or beds placed one above the other. These strata or layers are very much mixed, and their direction, matter, thickness, and relative position, vary considerably in different places. These strata are divided into seven classes. (1.) Black earth is composed of putrified vegetable and animal substances. It contains many salts, and much inflammable matter. This is what is commonly called mould. (2.) Clay is more compact than black earth, and retains water longer on its surface. (3.) Sandy earth is hard, light, and dry; it neither retains water, nor is dissolved in it, It is the worst kind of earth, though some kinds of plants may grow in it. (4.) Marle is softer, more mealy, less hard, and attracts moisture better. (5.) Bog, or moss earth, contains a vitriolic salt, which is too acid for plants. (6.) Chalk is dry, hard, and brittle: not> withstanding a few plants can thrive in it. (7.) Scubrous, or stony earth. The smoothest stones, however bare of earth, are at least covered with moss, which is a mere vegetable production: and birch is known to grow between stones, and in the clefts of rocks, and grows also to a considerable height.

9. The surface of the globe considered with relation to its inequalities, is divided into highland, lowland, and the bottom of the sea. 1. Highland, comprises, (1.) Alpine Hand, composed of mountain groups, or series of mountain chains; (2.) Mountain chains, formed by a series of those still more simple inequalities called, (3.) Mountains: in the former are considered their length, height, form, and connexion; the parts of the latter are the foot, the acclivity and the summit. 2. Lowland, comprises those extensive flat tracts which are almost entirely destitute of small mountain groups. 3. To the bottom of the sea, be