where it makes its first settlement, the lighter particles running forwards with the water into the _middle pit_, and thence into the third, where what is called the slime, settles. From these pits the ore is carried into a large vat, called the _keeve_, where it is washed and rendered clean enough for the smelting house. Most of the tin mines now working have steam engines, the advantages of which have proved a great benefit to the proprietors of them.” The famous _Wood Tin_, as it is called, has frequently been found in the stream works. It nearly resembles the colour of _Hæmatites_, with fine streaks, or _Striæ_, converging to the different centres like the radiated zeolite. From the experiments of the celebrated Klaproth, wood tin was found to yield 63 parts in a hundred of tin. The most general state in which the tin of Cornwall is found, is the _calciform_, the greater quantity of ore being indurated, or glass-like; and its most prevalent matrix is either an argillaceous or a silicious substance, or a stone composed of both, and called by the miners _caple_: none of the calcareous _genus_ ever appear contiguous to the ore, except the fluors.” The discovery of the _Copper Mines_ in Cornwall is of a much later date than those of tin, being about the year 1690. Although the propriety of searching was strongly recommended by _Norden_ to King James, many years expired before the real value of the copper mines was discovered. Subsequent improvements and perseverance have rendered the copper mines one of the most important branches of commerce in this county; and the quantity of that valuable ore, now annually raised, is said to be worth, upon a moderate calculation, the sum of £350,000, or £90,000 greater than the value of tin. Copper ores are found in Cornwall, in great abundance and variety. Native copper is sometimes found on the sides of fissures in thin films, deposited by the impregnated water that runs from the lodes. Veins of copper are also frequently discovered in cliffs that are left bare by the sea, but the most certain sign of a rich ore is an earthy ocherous stone, called _Gossan_, of a ruddy colour, and crumbles like the rust of iron. Another sign of the presence of copper is, when the ground is inclinable to an easy free working blue _Killas_, intermixed with white clay. A white crystaline stone is also found to contain a great quantity of yellow copper. The lodes of copper ore generally lie deeper than those of tin, and its ores are mostly of the pyritous and sulphurated kinds, with more or less arsenic. “The lodes, both of tin and copper, appear most frequently to have granite for their country, and to make an angle from 60° to 76° with the horizon.” The _matrices_ of copper ore are very numerous. Among the blue ores, there is one of an extremely fine blue earth. The grey ore is frequently spotted with yellow and purple, but is deemed richest when of an uniform colour throughout.