as it is variously called, suspended from the great beam, with which it rises and falls, bringing the pins p and k, at the proper moment, in contact with the handles k k and nn of the valves, moving them in the proper direction and to the proper extent. A lever safety-valve is here used, at

the suggestion, it is said, of Desaguliers. The piston was packed with leather or with rope, and lubricated with tal

low.

After the death of Beighton, the atmospheric engine of Newcomen retained its then standard form for many years, and came into extensive use in all the mining districts, particularly in Cornwall, and was also applied occasionally to the drainage of wet lands, to the supply of water to towns, and it was even proposed by Hulls to be used for ship-propulsion.

The proportions of the engines had been determined in a hap-hazard way, and they were in many cases very unsafe. John Smeaton, the most distinguished engineer of his time, finally, in 1769, experimentally determined proper proportions, and built several of these engines of very considerable size. He built his engines with steam-cylinders of greater length of stroke than had been customary, and gave them such dimensions as, by giving a greater excess of pressure on the steam-side, enabled him to obtain a greatlyincreased speed of piston. The first of his new style of engine was erected at Long Benton, near Newcastle-uponTyne, in 1774.

Fig. 21 illustrates its principal characteristic features. The boiler is not shown.

The steam is led to the engine through the pipe, C, and is regulated by turning the cock in the receiver, D, which connects with the steam-cylinder by the pipe, E, which latter pipe rises a little way above the bottom of the cylinder, F, in order that it may not drain off the injection-water into the steam-pipe and receiver.

The steam-cylinder, about ten feet in length, is fitted with a carefully-made piston, G, having a flanch rising four or five inches and extending completely around its circumference, and nearly in contact with the interior surface of the cylinder. Between this flanch and the cylinder is driven a "packing" of oakum, which is held in place by weights; this prevents the leakage of air, water, or steam, past the piston, as it rises and falls in the cylinder at each stroke of the engine. The chain and piston-rod connect the piston to the beam, II. The arch-heads at each end of the beam keep the chains of the piston-rod and the pump-rods perpendicular and in line.

A "jack-head" pump, N, is driven by a small beam deriving its motion from the plug-rod at g, raises the water

1 A fac-simile of a sketch in Galloway's "On the Steam-Engine," etc.

required for condensing the steam, and keeps the cistern, O, supplied. This "jack-head cistern" is sufficiently elevated to give the water entering the cylinder the velocity requisite

to secure prompt condensation. A waste-pipe carries away any surplus water. The injection-water is led from the cistern by the pipe, PP, which is two or three inches in diam

eter, and the flow of water is regulated by the injectioncock, r. The cap at the end, d, is pierced with several holes, and the stream thus divided rises in jets when admitted, and, striking the lower side of the piston, the spray thus produced very rapidly condenses the steam, and produces a vacuum beneath the piston. The valve, e, on the upper end of the injection-pipe, is a check-valve, to prevent leakage into the engine when the latter is not in operation. The little pipe, f, supplies water to the upper side of the piston, and, keeping it flooded, prevents the entrance of air when the packing is not perfectly tight.

The "working-plug," or plug-rod, Q, is a piece of timber slit vertically, and carrying pins which engage the handles of the valves, opening and closing them at the proper times. The steam-cock, or regulator, has a handle, 7, by which it is moved. The iron rod, i i, or spanner, gives motion to the handle, h.

The vibrating lever, k l, called the Y, or the "tumblingbob," moves on the pins, m n, and is worked by the levers, op, which in turn are moved by the plug-tree. When o is depressed, the loaded end, k, is given the position seen in the sketch, and the leg of the Y strikes the spanner, i i, and, opening the steam-valve, the piston at once rises as steam enters the cylinder, until another pin on the plug-rod raises the piece, P, and closes the regulator again. The lever, qr, connects with the injection-cock, and is moved, when, as the piston rises, the end, 7, is struck by a pin on the plug-rod, and the cock is opened and a vacuum produced. The cock is closed on the descent of the plug-tree with the piston. An eduction-pipe, R, fitted with a clock, conveys away the water in the cylinder at the end of each down-stroke; the water thus removed is collected in the hot-well, S, and is used as feed-water for the boiler, to which it is conveyed by the pipe T. At each down-stroke, while the water passes out through R, the air which may have collected in the cylinder is driven out through the "snift

ing-valve," 8. The steam-cylinder is supported on strong beams, tt; it has around its upper edge a guard, v, of lead, which prevents the overflow of the water on the top of the piston. The excess of this water flows away to the hot, well through the pipe W.

Catch-pins, x, are provided, to prevent the beam descending too far should the engine make too long a stroke; two wooden springs, yy, receive the blow. The great beam is carried on sectors, zz, to diminish losses by friction.

The boilers of Newcomen's earlier engines were made of copper where in contact with the products of combustion, and their upper parts were of lead. Subsequently, sheetiron was substituted. The steam-space in the boiler was made of 8 or 10 times the capacity of the cylinder of the engine. Even in Smeaton's time, a chimney-damper was not used, and the supply of steam was consequently very variable. In the earlier engines, the cylinder was placed on the boiler; afterward, they were placed separately, and supported on a foundation of masonry. The injection or "jack-head" cistern was placed from 12 to 30 feet above the engine, the velocity due the greater altitude. being found to give the most perfect distribution of the water and the promptest condensation.

Smeaton covered the lower side of his steam-pistons with wooden plank about 24 inches thick, in order that it should absorb and waste less heat than when the iron was directly exposed to the steam. Mr. Beighton was the first to use the water of condensation for feeding the boiler, taking it directly from the eduction-pipe, or the "hot-well." Where only a sufficient amount of pure water could be obtained for