DRAINAGE.] MINING 457 in vein-mining the skip and kibble still prevail in England, the managers are beginning to recognize the advantages of the cage am equip their mines with more modern appliances than have hithertc been customary. The cages used in the mines on the Comstock lode are very light and simple in construction, as will be seen froir fig. 86. The cage in fact is a mere timber platform, 5 feet by 4
FIG. 86. Cage used in Comstock Lode. resting on iron bars p, and supported by iron rods on each side. It is provided with a sheet-iron bonnet to protect the men if they are inside, and also with safety catches t, t, which come into play if the rope breaks. The hand levers k, k at the ends of the cage raise up blocks which keep the car in its place during the ascent or descent ; g, g are guides for the end of the crossbar b ; c, bar working teeth t,t by levers; /, "ear" or "shoe" embracing the guide-rod in shaft ; r, lifting bar ; s, strong spring. The most important details concerning the use of cages, ropes, and other hoisting appliances such as pulleys, pulley-frames, detaching hooks, and winding engines, have already been set forth in the article COAL, vol. vi. p. 74; and it is therefore needless to repeat these particulars, especially as the art of winding mineral cheaply, speedily, and safely has been carried to a far greater pitch of perfection in collieries than in the majority of metal mines. It is often convenient to fix winding engines underground for the purpose of sinking shafts and winzes, and drive them by com pressed air brought down in pipes from the surface. Koepe The Koepe system of winding, which appears to be viewed with system, favour on the Continent, consists in having what is practically an endless rope with one large sheave over the shaft, in the place of the two drums. There are two cages, and the rope below them acts as a counterbalance, so that the load is uniform throughout. .Ian- The most novel hoisting apparatus is that of M. Blanchet (CoAL, chet s vo i. vj. p. 76^ w hich has now been regularly at work in the Hot- method, tingucr shaft at ^Ipinac in France for the last six years. M. Blanchet s method consists in fixing in the shaft a large pipe in which is arranged a piston ; from this is suspended a cage carrying waggons. By exhausting the air above the piston the load is gradually forced up by the atmospheric pressure below it. The Hottinguer shaft is 660 yards deep, and the pipe is 5 feet 3 inches in diameter, made up of a succession of cylinders of sheet-iron about T inch thick and 4 feet 4 inches high, joined by flanges and bolts. The 485 rings composing the long pipe weigh altogether 418 statute tons. The cage has nine decks, and arrangements are made for unloading three at a time ; each waggon holds half a ton, so that the total useful load is 4 tons. The speed of hoisting is 20 feet per second. If two hoisting pipes are connected the dead weights may be made to balance each other, and the power required is simply that which is necessary to overcome the weight of the useful load. All the men prefer the pneumatic hoist to the ordinary cage for descending and ascending the mine, and are regularly lowered and raised by it. The advantages claimed by M. Blanchet for this system are (1) the possibility of hoisting from depths at which rope-winding would no longer be practicable ; (2) getting rid of the costly ropes and dangers connected with rope- winding ; (3) better utilization of the engine power ; (4) improve ment of the ventilation and diminution of the amount of fire-damp. 10. Drainage. The mineral having been raised to the surface, the task of the miner might appear to be at an end ; but this is not the case, for it is further necessary that he should keep his mine free from water and foul air. These two indispensable operations of draining and ventilating frequently require special appliances which add considerably to the general cost of mining. In all cases where it is possible, endeavours should be Drainaca. made to keep the water out of a mine, so as to save the expense of pumping it ; and the method of putting in a watertight lining (tubbing) in a shaft has been already described (CoAL, vol. vi. p. 62). When large streams of water happen to be intersected by underground work ings, and threaten to overpower the available pumping machinery, or when it is advisable to save the expense of draining abandoned workings, the entry of this water into the mine may often be prevented by stoppings, called dams, constructed of timber or brickwork. In spite of all precautions, the miner generally has to contend with water which percolates into the workings. Four methods of getting rid of this water are available, viz., adits, siphons, winding machinery, and pumps. An adit, day-level, or sough is a nearly horizontal tunnel Adits, with one end opening at the surface, allowing the water to drain away naturally. In hilly countries mines are often worked entirely by adits, and even when a mine is deepened below the drainage level the utility of the adit is still threefold : it lessens the quantity of water which tends to percolate into the lower workings ; it lessens the depths to which the water has to be pumped ; and, by furnishing a certain amount of fall, it enables water to be applied as power. On account of these important advantages some very long and costly adits have been driven for the purpose of aiding the miners in certain metalliferous districts. Thus in the Harz the Ernest Augustus adit ("Ernst August Stolln ") has been driven a distance of nearly 6 J miles into the Klaus- thai district. The total length of the adit, including the branclwjs, is no less than 14 miles. It intersects many of the lodes at a depth of upwards of 400 yards from the surface. The total cost of this adit is estimated at 85,500. Another long adit is the celebrated "Rothschonberger Stolln," which unwaters some of the most important mines at Freiberg in Saxony. The length of the main or trunk adit is more than 8 miles ; the gradient of the greater part of it is only 1 18 inch in 100 ya.vds. The branches of this adit among the mines are more than 16 miles in length, so that the total length of the main adit with its branches amounts to nearly 25 miles. Many of the mines are now drained naturally to a depth of 250 to 300 yards. The cost of the main tunnel was 359,334, or nearly 24 per yard, but this includes the cost of eight shafts, heavy expenses for pumping from these shafts, the walling of the adit for jj mile, and all general expenses. The length of time occupied in driving this adit was thirty-three years. The "Kaiser Josef II. Erbstolln " in Hungary is another remarkable mining tunnel, which was commenced in 1782, and com pleted in 1878 at a total cost of 4,599,000 florins. It is 10| miles in length, extending from the valley of the river Gran to the town of Schemnitz, where it intersects the lodes at depths varying from 300 to 600 yards according to the contour of the surface. In Cornwall the Great County adit was driven for the purpose of relieving the Gwennap mines of their water, and it was pushed on nearly to Redruth. This adit dili ers from the great works under taken in Germany by the fact that it commences in the mining district, and, though the length of all the drivages amounts to more
- han 30 miles, the water from the most distant mine does not run
more than about 6 miles before reaching daylight. The average depth is only 70 or 80 yards from the surface. In fact this great adit, though a work of great utility when the Gwennap district was in a flourishing condition, is merely a network of comparatively shallow drivages, often along the lodes themselves, among the mines, and therefore for boldness of execution cannot for one moment be compared to the great Schemnitz, Freiberg, and vlausthal drainage tunnels wJrich have just been mentioned. The 31ackett Level in Northumberlrnd is an adit which has been Iriven a distance of about 4f miles, and it will l.nve to be extended ibout 2 miles further before reaching Allenheads. Its depth from he surface at this place will be about 200 yards. The main part of the Halkyn tunnel in Flintshire is 2 miles ^256 yards in length, and the branch driven out to Rhosesmor mine intersected the vein at a distance of 809 yards, making a total of about 3J miles. The greatest depth from the surface s 230 yards, and the average depth in Halkyn Mountain about
XVI. 58