238. _TIN is a white metal, somewhat like silver in appearance, but is considerably lighter, and makes a squeaking or crackling noise when bent. It is very soft and ductile, and has but little elasticity._ _This metal is always found either in a state of oxide (21), or in combination with sulphur and copper; and is about seven times as heavy as water._ The principal tin mines which are known to us are those of Cornwall, Devonshire, Germany; the island of Banca, and peninsula of Malacca, in India; and Chili and Mexico in America. Of these the most celebrated are the mines of Cornwall, which are known to have been worked before the commencement of the Christian era. Diodorus Siculus, who wrote forty years before the birth of Christ, gives an account of these mines, and says that their produce was conveyed to Gaul, and thence to different parts of Italy. This species of metal was used in the time of Moses, and is mentioned in the writings of Homer. Tin is found in veins, or beds, but chiefly in veins, running through granite and other rocks. In some of the valleys and low grounds of Cornwall, the tin ore is found in rounded grains and masses. In these situations, small grains of gold are sometimes found with it. To separate the tin from earthy and other matters with which it is intermixed, streams of water are passed over them; and these deposits have the name of _stream─works_. When the tin ore has been dug from the earth, or has been collected at these stream─works, it is thrown into heaps, and broken to pieces. After this it is washed, and subsequently roasted in an intense heat, for the purpose of dissipating some of the substances with which it is combined. It is lastly melted in a furnace, and thereby reduced to a metallic state. The metal is then poured into quadrangular moulds of stone, each containing about 320 pounds weight. These have the denomination of _block─tin_, and are stamped by officers of the Duke of Cornwall, with the impression of a lion, the arms of that duchy. This is rendered a necessary operation before the tin can be offered for sale; and on stamping, it pays a duty of four shillings per hundred weight to the Prince of Wales, as Duke of Cornwall, who thence derives a very considerable income.