According to Aristotle, the tin mines of Cornwall were known and worked in his time. Diodorus Siculus, who wrote about forty years before the Christian era, gives an account of working these mines: he says, that their produce was conveyed to Gaul, and thence to different parts of Italy. The miners of Cornwall were so celebrated for their knowledge of working metals, that, about the middle of the seventeenth century, the renowned Becher, a physician of Spire, and tutor of Stahl, came over to this country on purpose to visit them; and it is reported of him, that, when he had seen them, he exclaimed, He who was a _teacher_ at home, was a _learner_ when he came there. About 3,000 tons of tin are furnished annually in Cornwall, two-fifths of which are usually exported to India by the East India Company. There are two kinds of tin known in commerce, namely, _block_ tin, and _grain_ tin. Block tin is procured from the common tin ore, and usually cast in blocks of about 320 pounds weight. It is taken to the proper offices to be assayed, where it receives the impression of a lion rampant, being the arms of the Duke of Cornwall, pays a duty of four shillings per hundred weight to the Duke, and then becomes legally salable. Grain tin is found in small particles, in what is called the _stream tin ore_. It appears to have been washed from its original bed in remote ages. This kind of tin owes its superiority, not only to the purity of the ore, but to the care with which it is washed and refined. _Lead_ is of a blueish white color, scarcely sonorous, unelastic, and, being the softest of all metals, yields readily to the hammer. It generally contains a small quantity of silver. An alloy of this metal with tin forms pewter, and in different proportions soft solder. Its specific gravity is 11.35. Lead ore is very abundant in Scotland, the western parts of Northumberland and Durham, Derbyshire, and many other parts of the world. The lead found in these counties occurs on the estates of Colonel Beaumont, and of those of the late Lord Derwentwater: the last of these were forfeited to Government; and are now in the possession of Greenwich Hospital. Lead was known in the time of Moses, and was in common use among the ancients. The Romans sheathed the bottoms of their ships with it, fastened by nails made with bronze. During the first century, at Rome, it was twenty-four times the price it is now in Europe; whereas tin was only eight times its present price.