When the influx of water in a mine becomes at all considerable, recourse must be had to the power either of a waterwheel or a steam engine to discharge it to the surface. If a water-wheel is used instead of horse-power, pumps are in that case fixed in the shaft, pro portioned in size to the quantity of water to be drawn, 10 or 12 inches in diameter being a very common size where there is only a moderate influx. The pumps used in mines do not act like common household pumps ; they are arranged in ' lifts' or columns, of considerable height, often indeed from 20 to 30 fathoms, the water being discharged into cisterns placed at the foot of each. The pumps are now commonly made of iron. The whole column of pumps in a shaft is commonly worked by a single pump-rod, which goes down the middle of it and communicates with each column by a rod attached to its side. The steam-engine has long been the great auxiliary of the English miner, both for drawing up the minerals and for discharging the water.
The mode of support used in mines is of three kinds—by leaving pillars of the vein, for which purpose the poorer masses are of course selected ; by timbering ; and by walling either with brick or stone. Timbering is a very common and convenient plan, and consists of timber frame-work and boards. Shafts and levels are sometimes also supported by walling. The ventilation of mines is most generally and most effectually accomplished rather by a judicious arrangement of the works and fre quent communication with the surface than by mechanical means, although it sometimes becomes necessary to resort to the latter. The general mode of working and ventilating coal mines is noticed under Coen.
The ore raised to the surface is enormous in some mines. At the Consolidated Mines in Cornwall it has sometimes amounted to 200 tons a day, of which three-fourths is earth or rubbish. To remove this rubbish is the
object of dressing, for which purpose the lumps are taken to the 'dressing floors,' near the mouths of the principal shafts and levels, and are there broken with hammers. The ore is then picked out by boys and women, and fur ther subjected to various processes of crush ing, stamping, and washing. When the metallic portions are as far separated as it is possible for them to be by these processes, they are roasted in furnaces, to drive off the oxygen and all other chemical substances that may be combined with them.
During the year 1850, a number of new English mines were opened, and many old mines were brought more prominently than before into notice. As a field of investment and speculation, English mines, after a long period of depression, have lately revived; and there are not wanting indications that some thing of the recklessness of railway speculation will soon be observable in mining transac tions. There are public manias of this kind which seem tolsupervene at intervals of a few years. There were dividends, to the amount of 213,570/., paid in 42 Devon and Cornwall mines in 1850 ; being larger in amount than in the four preceding years. The Devon Great Consols Mine, near Tavistock, is at the pre sent time the richest in the United Kingdom; no other mine yields so large a return for the capital sunk in working it; and the value of the shares, in respect to premium on the original price, excels any thing that the rail way ferment has presented to us, either in England or elsewhere. Most of the best mines in Devon and Cornwall yield both tin and copper, the copper being generally found below the tin.
Various details relating to English mining will be found under COPPER; CORNWALL; DERBYSHIRE ; IRON ; LEAD ; &C.