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 greatly-increased speed of piston. The first of his new style of engine was erected at Long Benton, near Newcastle-upon-Tyne, in 1774.

[Fig. 21][31] illustrates its principal characteristic features. The boiler is not shown.

Fig. 21.—Smeaton’s Newcomen Engine.

[Large scale image.]

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, I I. 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 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, P P, which is two or three inches in diameter, and the flow of water is regulated by the injection-cock, 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.