COLLIERY T3 introduced during the last 10 or 15 years. They are direct-acting force pumps, but instead of being connected with the engine by rods, the steam is carried in pipes to the bottom of the mine, where both steam cylinder and pump are connected by a very simple arrangement, as a single piece of machinery. The Allison and Bannan pump is generally used where pumps of this class are employed in anthracite mines, while the Cameron pump is used in England and this country for the same purposes. One of these has recently been placed in the mines at Bishop Auckland, England, with a steam cyl- inder of 26 in. and a pump barrel of 6 in. diam- eter, with 6 ft. stroke to each. This pump throws a steady stream of 120 gallons per min- ute up a vertical height of 1,040 ft. in a single lift, under a water pressure of 700 Ibs. per square inch. At the close of 1870, 130 of these pumps were at work in the mines near New- castle and Durham, England. The raising of coal from deep mines is now almost exclusively done by cages, on the principle of the elevators used in hotels. These cages are moved with the speed of a railroad train. They are pro- vided with " shoes," or projecting guide slots or holes, which move on or in guides of wood, FIG. ia Underground Mining Pump. iron, or rope, extending from the top to the bottom of the pit. These cages are in one or two stories, and carry one or two mine cars on each story. They are provided with rails cor- responding to the track both at the bottom and top of the pit. The time occupied in shifting the cars and hoisting through 2,400 ft., in the Rosebridge pits, near Wigan in England, is less than one minute. When the water is properly dammed back there is generally very little in deep pits ; and when the mines are dry and dusty, as they very generally are, there is scarcely enough water to moisten the air and allay the dust, if properly distributed over the mines, which however is rarely done. But when the water is in excess, and not very abundant, a tank may be placed beneath the cage, which dips into the water and fills through self-acting valves at the bottom of the pit, and discharges by automatic arrangement at the top. This is simple, cheaper, and better than pumps in very deep mines, when the water is not excessive; but when it is abundant, the pump is the most available. The cages are now generally raised by means of two engines or steam cylinders connected directly, without spur gearing, to the cranks of the drum on which the rope is wound. The engines are connected with link motion, so that one is on the "live centre" or half stroke while the other is on the " dead centre " or full stroke, and are reversed at each ascent and descent of the cages, of which there are always two, one descending while the other is ascending. Round wire or steel ropes are generally used; but there can be no doubt that flat steel ropes are the best for deep pits. These should be made of uniform steel, and composed of several round ropes combined, or served together with steel wire, and very carefully stretched and adjust- ed before they are put to work. Flat ropes work on or in grooved drums, and lap on them- selves. Thus at starting, when the strain on the engines is the hardest, the diameter of the drum is the smallest, and much in favor of the lift; while the descending car and cage, which act as counter-balance, are on the larger diameter of the drum, because on this side the rope has lapped on itself and increased the diameter say two inches at each revolution, so that if the drum or groove was 10 ft. in diameter at starting the cage from the bottom, and the pit 2,000 ft. deep, its diameter would be about 20 ft. when the cage arrived on the top. Another very desirable method of elevating coal or water is the "pneumatic lift," now in general use to supply the new material to the top of blast furnaces, and in a few cases to elevate coal in pits. For very deep pits this seems to be an admirable method, and where a pair of circular pits are used, with brick and cast-iron lining, it is the most economical method, both in regard to first cost and permanent operation. The plan is very simple, but difficult to explain without elaborate engravings. The elevation may be effected by means of suction or compression of the air, as now practised hi the pneumatic des- patch tubes. This mode of elevating coal or water may be extended to any practicable depth, or perhaps as deep as the English or French and Belgian coal basins descend below the sea level, without complicated machinery, and with perfect safety ; while the power em- ployed to raise the material supplies the venti- lation, because the entire area of the pits can be used to supply air under pressure or vacuum. Thus compressed air may be used for all under- ground purposes, except the mere handling and breaking down of the coal, as machinery is successfully used for "undermining," which is the most laborious and costly item in mining bituminous coal ; while in anthracite mines drilling holes for blasting is the most laborious part, and this also can be done more effective- ly and cheaply by machinery. (See MINE.) The increase of temperature is the only great apparent obstacle to increased depth of pits. According to English experience, the tempera- ture rises 1 degree for every 60 ft. of depth. It appears that the old Kuttenberger pit, in Bohemia, was abandoned at 3,778 ft. on ac- count of the high temperature at that depth ;
