THE SERGEANT ROCK DRILL.
This district is the only one in the United States where the man-engine has been used; but as the shafts were sunk deeper and deeper, it was found that even this method was not sufficiently rapid, and the men are now lowered into the mines by cages or skips. A “cage” is simply the miners’ name for the ordinary elevator when used underground, and has developed from the bucket in use at the beginning of the century. A “skip” is a car especially designed for use on an incline. The roadway upon which the skip runs is so planned, at the top of the shaft, that the rear wheels run upon a track raised above the one over which the front wheels pass, so that the rear end is elevated and the skip is dumped automatically. At the De Beers diamond mines in South Africa are two of these skips which hold nearly five tons of rock each. At the bottom of the shaft are chutes containing the rock, and when the skip is in position a man pulls a lever, allowing the ore to run into it. Another pull closes the chute, a button is touched which rings a bell in the engine-room, and the skip starts up the shaft. At the top it dumps itself and returns to be filled again. In the mean time the other skip has been filled and is going up while the first is coming down. With these two skips, making ninety-two trips an hour, over four thousand tons of rock have been hoisted in less than twelve hours, from a depth of 1250 feet.
To handle these enormous quantities tremendous hoisting engines are used. At the Calumet and Hecla mines is a pair of quadruple expansion engines which will lift cages, carrying six tons of ore, a mile in a minute and a half. The “Modoc” hoist, built for the Anaconda Mining Company of Butte, Montana, is the largest hoist in the world. It is a double compound beam engine, and is designed to be used in sinking to a depth of 6000 feet. This machine weighs four hundred tons, and has seven separate subordinate engines for use in operating it. Think of it! An engine so ponderous that smaller engines are necessary to apply the clutches that set the reels in motion; other engines set the brakes, and another reverses the action, if need be. All these are controlled by levers operated from the engineer’s platform, the “runner” having one foot and seven hand levers to handle. Besides these there are two indicator discs, directly in front, requiring constant attention, for these show the exact position of the cage in the shaft. Yet such wonderful skill have the runners in the control of these veritable flying machines that they instantly interpret the complicated signals, and drop the cage with such exactness that the car of ore is run from the track in the level to the track on the cage, almost without a jar.
INGERSOLL-SERGEANT STEAM-DRIVEN AIR COMPRESSOR.
Nor is the hoist the only large machine necessary in the equipment of the modern mining plant, for in sinking to great depths vast quantities of water have to be removed. The Chapin Mining Company, at Iron Mountain, Mich., have one of the largest pumping engines in the world. This engine is located on the surface, driving the pumps after the Cornish style, though it would be difficult to see much of the pump of 1801 in this magnificent machine. With a ten-foot stroke it conveys the power to the pumps through a walking beam weighing a hundred tons. In an hour it will raise nearly 200,000 gallons of water from a depth of a quarter of a mile.
DRIVING A RAILWAY TUNNEL WITH THE INGERSOLL “ECLIPSE” ROCK DRILL.
Imagine the miner of 1800 “softening by fire” sufficient ore to supply a modern hoist. For the mines which now turn out 2000 tons a day can by no means be counted on one’s fingers, and 2000 tons means more than a foot deep over a whole city block. Before the middle of the century the use of powder and drill had largely increased, and in 1845 an attempt was made to aid the man behind the drill with a machine which swung a hammer by steam power. In 1805 a machine was invented using compressed air in a cylinder, and this was gradually improved until it became a success in 1861, in the Mont Cenis tunnel. As finally employed, the power drill is practically a small engine, the drill being attached to the piston rod and moved rapidly back and forth by compressed air or steam. The machine has three functions: to strike the blow, turn the drill, and advance it, as the hole is driven deeper and deeper.
