In coal mining the effect of the use of electrical machinery has been revolutionary in recent years, particularly in the development of electric coal cutters. The old method of picking out coal by hand, where the miner labored with the heavy pick, working in all manner of cramped and dangerous positions, was supplanted a few years ago by the "puncher" machine, worked by steam or compressed air. With these machines the coal was picked out just as in the case of the hand method, except that the energy was derived from some power other than muscular. So that while these machines worked more rapidly than the hand picks, they utilized the same general principle in applying their energy. Within recent years, however, various coal-cutting machines have been devised, with which the coal was actually cut, or sawed out, these machines being peculiarly well adapted to using the electric current. The most practical and popular form of machine is one in which the sawing is done by an endless chain, the links of which are provided with a cutting blade. These have been very generally replacing the compressed-air or pick type of machine, and their popularity accounts largely for the enormous increase in the use of coal-mining machinery during the past decade. Thus in 1898 there were 2,622 coal-mining machines in use in the United States. Four years later this number had more than doubled, the increase being due largely to the adoption of chain machines. Like electric locomotives, and for similar reasons, the coal-cutting machines are low, broad, flat machines, from eighteen to twenty-eight inches high. They rest upon a flat shoeboard that can be moved easily along the face of the coal. An ordinary machine weighs in the neighborhood of a ton, and requires two men to operate. The apparatus is described briefly as follows: "On an outside frame, consisting of two steel channel bars and two angle irons riveted to steel cross ties, rests a sliding frame consisting of a heavy channel or centre rail, to which is bolted the cutter head. The cutter head is made entirely of two milled steel plates, which bolt together, forming the front guide for the cutter chain. This chain, which is made of solid cast steel links connected by drop forge straps, is carried around idlers or sprockets placed at each end of the cutter head and along the chain guides at the side to the rear of the machine, where it engages with and receives its power from a third sprocket, under the motor. The electric motor, which is of ironclad multipolar type, rests upon a steel carriage, which forms the bearing for the main shaft.... A reversing switch is provided, so that the truck can travel in either direction, and when the machine has reached its stopping point, either forward or backward, it is checked by an automatic cut-off. The return travel is made in about one-fourth of the time required to make the cut."