The condenser, F F, has a pipe enter ing it, and turned up within it ; the pipe opens to the water in its condensing cis tern, G G, and has a cock in its outer end, which regulates the quantity of water the pipe will admit, or closes it entirely ; the cock has a long handle coming up out of the water, which is not seen in the sec tion ; but is denoted by o, in Plate I.
Suppose every thing in the position of the section, the operation of the engine is as follows : when the water in the boi ler A, Plate I. is heated by the fire made under it at X, the heat which enters into combination with the water causes it to expand and form steam ; in this state it raises and fills the boiler, and thence through the pipe, e, enters between the jacket, c c, and the cylinder; before the engine can be worked, the steam must be heated, until it is expanded so much, that it will rush forcibly out of the boiler when permitted. The steam also passes through the short pipe, before described, into the passage, h, and thence through the crook ed passage in the cock, F, to the pipe, g g, and the bottom of the cylinder, though it will not enter the cylinder, be cause it is yet filled with air.
The person who attends the engine must now open the cock, N ; this admits the steam from the boiler into the con denser ; it rushes violently through the pipe, p p, into the condenser, F F. driving the air it contained through the three valves, i, 1, and to, which it opens, into the cistern, 1, (where it is open to the at mosphere. the lid of that cistern being only laid on and not fitting tight :) this operation (called blowing through) con tinued for a few seconds, expels all the air from the condenser, and fills it with hot steam ; the cock. N, is now closed, and the injection cock. of which 0. Plate I. is the handle, is opened ; this allows a small stream of cold water, from the cis tern, G, to enter into the condenser, and condenses the steam, or cools it, and it instantly contracts into the same space it originally occupied when in the boiler, before it was heated. As the valve, 4 closes, it is evident that a vacuum will be caused in the condenser, as the small quantity of water produced from the steam, and the water injected into the condenser, falling down to the bottom, the air in the upper part of the cylin der will now expand itself into the con denser, through the pipe, f f, the cock, E, and pipe p p, and as it occupies more space than it did before, it will be con siderably rarefied; the stream, pressing with its full force against the lower side of the piston, will, perhaps, (now a rare faction is made above it.) overcome the resistance of the work and friction, and cause it to ascend, the air•pump rod and bucket moving with it ; when the pin, M, upon this rod, reaches the handle, K, it raises it up, and, by means of the rack and wheel shown in Plate 1. turns the cock, E, one-fourth of a revolution, bring ing its two passages into the position of fig. 2. Plate 11.
The operation is now reversed, the steam from the boiler going above the piston, and that steam, mixed with atmo spheric air beneath it, going to the con• denser, where the steam will be con densed, and a partial vacuum formed beneath the piston; the steam now presses it down, moving the beam fly wheel and other machinery it has to drive ; when the pin, L, on the air-pump rod arrives at the handle, K, it presses it down, and brings the cock into the posi tion of the figure 1, in which the piston will be driven up again At each stroke of the engine, when the piston rises, the valve, i, on the bucket of the air pump, will shut, and all the air and water con tained above the bucket will be lifted through the valves, m m, into the cistern, I ; at the same time a vacuum being made beneath the bucket, which is more per fect than that in the condenser, the valve, will be opened by the water and air in the condenser, which will enter the pump. On the ascent of the piston and
the air•piimp bucket, the valves, m m and i, will shut, the pressure which open ed them being removed, and the water and air in the pump pressing upon the valve, 1, will open it, and get through as the bucket descends : at its return, it raises the water and air above it as be fore. In this manner, when the engine has made a few strokes, all the air con tained in the engine at the commence ment of the operation will be pumped out the operation of the engine is now much more perfect. The instant the cock, E, is turned, so as to open a com munication from the cylinder full of steam to the condenser, the elasticity of the steam causes it to rush down the pipe, p p, into the condenser; when it arrives there, it meets the stream of the injection water, which condenses it, and the remaining steam in the cylinder fol lows it surprisingly quick, and in an in stant an almost perfect vacuum is formed in the cylinder, so that the steam acts with its whole force upon the piston, all resistance upon the other side being removed. The air pump now has only to draw off from the condenser the wa ter injected into it, the condensed steam, and a small quantity of gas, which goes from the boiler with the steam, and wilt not condense by the cold water ; these are delivered by the air pump into the cistern, 1, from which the air escapes, the cover not being tight (as before men tioned), the water which still continues hot runs off, when at a certain level, by a waste pipe, o, Plate 1. The water which is boiled off in steam from the boiler is renewed from this cistern by means of a small pump, P, Plate 1. which draws the water from it by a passage through the centre of the cast iron column, Q, which stands upon the end of the condensing cistern, GG, and sup ports the bearing for the main axis of the great beam, B ; the water is conveyed to the bottom of the column by a short pipe, r, and after going through the pump, P, is carried by the pipes, RR% to a cistern on the top of the vertical pipe, S, which leads into the boiler. The top of S is closed by a valve in the cis tern, which is raised by means of a lever, the tither end of which has a wire, y.