صور الصفحة
PDF
النشر الإلكتروني

Silver is a white rich metal, and, except gold, the finest and most ductile of any. There are filver mines in all parts of the world; but those of Peru, and fome other parts of America, particularly those of Potofi, are by far the richest, and yield the ore in as great plenty as when first discovered; with this only difference, that the veins, which were then almost on the surface of that famous mountain, are now funk so deep, that the workmen go down to them by a descent of almost four or five hundred steps.

СНАР. С.

OF COPPER AND IRON.

OPPER is a hard, dry, heavy, ductile metal, abounding in vitriol and ill-digefted fulphur, and found in moft parts of Europe, but particularly in Sweden. It is dug up in large fragments of ore, which are first beaten small, then washed to feparate the earthy parts from it, then finelted and caft into a kind of moulds to form large blocks, called falmons, or copper-cakes. This is the ordinary copper. There is a finer kind called rose copper,

and a still finer, called virgin copper, which is fometimes, but feldom, found pure in mines. It is the lowest-priced metal used for coin.

Iron is a hard, dry, fufible, and ductile metal, confifting of earth, falt, and fulphur, but all impure, ill-mixed, and ill-digefted, which renders it liable to ruft. By often heating it in the fire, hammering it, and letting it cool of itself, it is softened; by extinguishing it when hot in water, it is hardened.

There are feveral iron works in England; but the most confiderable are thofe in the forest of Dean, in Gloucestershire, where the ore is found in great abundance.

Though iron is the cheapest, it is certainly the most useful of all kinds of metal, and seems indifpenfibly necessary to the carrying on every art and manufacture. Nay it appears to be a great mean of polishing and civilizing mankind; at least much more fo than the more precious metals. There have been instances of nations poffeffed of great quantities of gold, who yet remained in a state of barbarifm. This, it is well known, was the cafe with the Americans, upon the first discovery of their country by Columbus. But there never was an inftance of a nation, which understood the art of manufacturing iron, that did not attain, in time, to at least some degree of civilization.

[blocks in formation]

СНАР. СІ.

OF LEAD, TIN, AND MERCURY.

LEAD is a coarfe, heavy, foft metal, containing a little mercury, fome fulphur, and a great deal of earth. It is found in most countries; but is particularly plentiful in England. The various purposes, to which it may be applied, are pretty generally known.

Tin is a whitish metal, not fo hard as filver, nor fo foft as lead; but though not fo foft, it is more eafily melted. The ftannaries of tin mines in Cornwall and Devonshire furnish the greatest part of the tin, which is confumed in all Europe. Six pounds of brass, and fifteen pounds of lead, to an hundred pounds of tin, make the compofition which is called pewter.

Mercury, or, as it is vulgarly called, quickfilver, is an imperfect metal, neither ductile, nor malleable, that is, neither capable of being drawn into length, nor fpread into breadth by the hammer. It confifts entirely of a fluid matter, refembling melted filver. It is found chiefly in Hungary, Spain, Italy, and Peru. The greatest part of what

is used in England is brought from the mines of Friuli in Italy.

Mercury is the heaviest of all metals except gold. It is also the most fluid of all bodies; that is, its parts cohere the least to each other, and are the most easily separated. It is extremely volatile, and may be turned into fume by a very gentle heat. It easily enters and closely adheres to gold, less easily to filver, with difficulty to copper, and to iron not at all.

CHAP. CII.

OF PRECIOUS STONES.

THE diamond, by the ancients called adamant, is the most valuable of all precious ftones. Its goodness confifts in its colour, luftre, and weight; and its defects are flaws, veins, fpecks of red or black fand, and a bluifn, or yellowish cast.

Diamonds are found only in the East-Indies, fometimes in mines, and fometimes in the fand of rivers. They are the hardest of all gems, infomuch that they can only be cut and ground by themselves, and their own fubftance.

[blocks in formation]

The manner of preparing them is first to rub them hard against each other, and the duft, which is thus rubbed off the ftones, ferves to grind and polifh them. This is done by means of a mill, which turns a wheel of foft iron, sprinkled over with diamond duft, mixed with oil of olives. The fame duft, well ground, and diluted with water and vinegar, is ufed in the fawing of diamonds; which is performed with an iron or brafs wire as fine as a hair.

The ruby, which is next in value and esteem to the diamond, is of a crimson colour, fomewhat inclining to purple. The garnet is fomewhat like it, and perhaps of the fame fpecies. The hyacinth is fometimes of a deep red, and sometimes of a yellow colour. The amethyst is of a bright purple, and the emerald of a grafs green. The Sapphire is a fky blue, and the beryl, a bluish green. The topaz or chryfolite is of a gold colour. These are all transparent.

There are others that are opaque, or only half tranfparent; fuch as the cornelian, which is the beft, and of a pale red, and fometimes bordering upon orange; the onyx, of a greyish cast; the turquoife, fomething between a blue and green; and the lapis lazuli, which is ftudded with spots of gold on an azure ground. CHAP.

« السابقةمتابعة »