The manner in which the steam and cold water are alternately admitted into the receiver A, remains to be explained. Upon the extremity of the axis S of the water wheel, a solid wooden wheel T is fixed; it is about four feet in diameter, and turns round with the water wheel. It is represented separately, as seen in the front; a, b, c, d, are four cleats, all or any number of which may be fixed on the wheel at a time. Each cleat has its corresponding blocks e, f, g, h, on the opposite surface of the wheel. The use of these is to work the engine. Thus, suppose the water wheel, and this wheel T, with all the revolving apparatus, is turning round, one of the cleats a meets in its rota tion with a lever, which it lifts up, and this opens the steam valve D by a rod of communication reaching to the handle of the axis K. The steam consequently passes into the receiver A, and the steam valve shuts again, as soon as the cleat a of the wheel 'I' has pass ed away from the lever by the motion of the wheel. All this time the corresponding block e on the other side of the wheel 'I' had been operating to raise up the loaded lever which forms the handle of the forcing pump: and at the same instant that the steam valve I) is shut, as above mentioned, the block e quits the loaded lever, after having raised it up, and leaves it to descend suddenly by its own weight. This de presses the forcer of the pump and thereby throws a jet of cold water up into the receiver A, and it falls in a shower of drops through the steam which fills the receiver, so as to cool and condense the steam and make a vacuum.
The pressure of the atmosphere upon the surface of the water in the cistern K then causes the water to mount up the perpendicular suction-pipe, through the valve G, towards the exhausted receiver.
When the engine is first set to work, the water wheel being motionless, the steam valve and injection pump are moved by hand, and if the engine has been long out of work, two or three strokes may be neces sary to raise the water to the top of the receiver A, so as to fill it full of water. As soon as this is the case, and the steam valve is opened to admit steam into the receiver, the whole contents of water, above the spout and valve F, then flows out of the receiver A, by its own gravity, into ihe upper cistern IL The water which is thus raised, is suffered to flow from the cistern upon the overshot water wheel W through a sluice; and by that means keeps the wheel in motion, and replenishes the lower cistern. There is no reservoir for the injection water; but the requi site quantity is driven up at each stroke; and as this is done by the sudden descent of the loaded lever of the pump, the water is injected very suddenly into the receiver." Before the improvements upon Savery's engine were proposed by Desaguliers, a very important in vention had been made by Mr. Thomas Newcomen,
an ironmonger in Dartmouth. There is reason to be lieve that this ingenious workman was occupied in the improvement of the steam engine as early as Mr. Savery. Switzer, indeed, who was a friend of Sa very's, and therefore not likely to make any statement injurious to his reputation, distinctly informs us that he had good authority for stating that Newcomen was as early in his invention as Savery; but that the latter being nearer the Court, obtained his patent before the other knew of it, on which account Newcomen was glad to come in as a partner in the patent which was granted to them in 1705.
Dr. Desagulicrs, however, has given a different ac count of the matter, and as the passage contains some interesting details, we shall give it in his own words. " Thomas Newcomen, ironmonger, and John Calley, glazier of Dartmouth (Anabaptists) made the several experiments in private, and having brought the en gine to work with a piston, &c. they, in the latter end of the year 1711, made proposals to draw the water at Griff in Warwickshire; but their invention meeting not with reception, in March following, through the acquaintance of Mr. Potter of Bromsgrove in Worces tershire, they bargained to draw water for Mr. Bach of Wolverhampton, where, after a great many labo rious attempts, they did make the engine work ; but not being either philosophers to understand the rea sons, or mathematicians enough to calculate the pow ers, and to proportion the parts, very luckily by acci dent found what they sought for. They were at a loss about the pumps, but being so near Birmingham, and having the assistance of so many admirable and inge nious workmen, they so soon came to the method of making the pump valves, clacks, and buckets, whereas they had but an imperfect notion of them before." The engine thus constructed has received the name of the atmospheric engine, in consequence of the power which is employed, being only the weight of the atmosphere, the steam exerting no force whatever either upon the surface of the water, or upon the pis ton, and having no other functions to hut that of forming a vacuum. Newcomer's engine, in its ori ginal state, is shown in Plate 1)V; Fig. 4. The steam generated in the boiler B, passes through the cock D into the steam cylinder A, beneath a piston S, which is attached by means of the piston rod r, to the great beam I, I. This beam or lever has at its extremities arch heads, upon which the chain R laps and unlaps itself during the motion of the beam round the fulcrum C, the chain being fixed at the upper end of the arched head. The cylinder A is surrounded with another cylinder ZZ, concentric with it, and communicating by a pipe F, with a reservoir G of cold water, while Its lower end communicates with the well 0, by ano ther pipe EE.