The writer encountered in the above operations is drawn to the surface by a powerful steam-engine erected on the shaft, which is so arranged a-e also to raise the coal and rubbish, for which purposo either " corves " or baskets are commonly employed. Supposing the above operations to have been successful as regards the prospects of the mine another shaft will now be commenced at some distance from the first, and when the communication between them has been effected, the one being made the downcast and the other tho upcast, the air is conducted from the latter to the former through all the herds and workings, which it must traverse in succession in consequence of " stoppings " or doors which are fixed in various places to obstruct its progress and give a proper direction to the current passing to the upca.at shaft. Till such communication can be formed, the first shaft may be divided by a or partition, and be made to answer the purposes of both ; some few coal-mines are indeed worked entirely in this manner, but the danger of explosion is considerable when the workings become extensive.
While the workings on the first scant of coal are thus going on, the shaft may be sunk to a second or third seam, where similar operations will be commenced, small underground pits or "staples " being sunk at intervals from the workings of the upper scam to those on the seam below, by which ventilation will be promoted. These operations, like those described in the former article, may be carried on indefinitely, and will thus in time form an extensive colliery. The regularity and uniformity of the working however are greatly modified by the occur rence of faults and other local accidents, and themselves are finally removed to such an extent as to cause subsidences of the roof and undulations of the floor, which present a most frightful appearance to the stranger.
The mode in which the pitman carries his excavation upon tho coal is by cutting a narrow fissure in the ream on each side of the bond, and undermining the coal between, finally detaching the great cubical mass thus circumscribed by putting in two or three shots, which are simultaneously fired at the top of the scam. From GO to SO or tons of coal may thus be brought down rat once, when it is put into cones drawn along a tram-road to the shaft, and thence raised by a steam-engine to the surface, where it is often passed over gratings or "'screens" in order to separate the small pulverised coal from the larger masses, which in coal countries are alone valuable.
In mines which are not endangered by explosive gases or "fire damp," the coal-miner or " pitman " is guided iu his operations by the usual subterranean light--a small candle stuck into a piece of moist clay ; but where the fire-damp is apprehended the safety-Lamp is used, which has long superseded tire primitive contrivance of tho the light of which was produced by the contact of a flint with the edge of a wheel kept in rapid motion. Notwithstanding the use of the Davy lamp, and the improvements which have taken place in ventila tion, accidents from explosion aro unfortunately still of frequent occurrence, although perhaps in most cases they may be traceable to some neglect or imprudence on the part of the men themselves. Attempta have recently been made to apply coal gas to tho lighting of tin-mines and coal-mines, both in England and 11111(114mo ; hut hitherto without success.
The quantity of coal raised in Great Britain in 1858, was not loss than (15,008,019 tons.
[Lesu: Red Lead.]