FIG. 3.
Fire and garden engines are only applications of the pump to different purposes. The fire-engine has generally two cylinders and pistons, and has moreover an air-chamber for the purpose of making the stream of water continuous. It acts in this way:—The water is forced by the power of those who are pumping the engine into a vessel air-tight and full of air, having an opening which joins the “hose” at its lower part; the result is, that as the water is forced in faster than it can well escape, the air above it—becoming greatly compressed, and by its expansion between each stroke of the pistons—forces the water out, and so continues the stream or jet. [Fig. 3] shows this air-chamber; a joins to the hose c, and b is in union with the forcing-pumps of the engine. The air is represented as it would be compressed to about half its bulk, for it at first filled all the air-chamber down to the openings.
VALVES.
FIG. 1.
FIG. 2.
