TIN, one of the seven perfect metals. See CHEMISTRY, n° 150, 203, 246, 285, 406. See also METALLURGY.
This metal is found very plentifully in the southern parts of Britain, particularly Cornwall, to which and Devonshire the mines are now principally confined. Though in itself the lightest, it is in its ore the heaviest of all the metals. It is very seldom, if ever, found pure, and the appearances of its ore are very different. The finest and richest are styled tin grains, or corns of tin, being crystals of a black colour of different sizes. It is also found in an heavy black stone, sometimes in a more porous yellow-coloured one, and is commonly intermixed with spar, arsenic, &c. Tin-mines are generally found on the sides of the hills, though veins sometimes pass through valleys or brooks between two hills, and may be traced to the opposite hill. The miners work with the utmost difficulty through hard rocks from three to 70 fathoms depth;
and it is no less troublesome, as well as dangerous, where the earth is loose and apt to crumble. The veins are of an uncertain thickness; from three inches to three feet. Tin grains or corns of tin yield five parts in eight of metal; whereas tin stones yield only from one in 30 to one in 60, and to one in 120; for these last are also wrought with some small profit. After melting it is called black tin; but before it can be exposed to sale it is carried to one of the five coinage-towns, where, after examination of a piece that is broke from the corner of a block, the arms of the duchy of Cornwall are impressed with an hammer, and then it is called white tin. The duty on coinage, which is four shillings on the hundred-weight, belongs to the prince of Wales as duke of Cornwall, and produces a revenue of upwards of 10,000l. per annum.