Steam-Engine. An arrangement of mechanism, by which, by the alternate generation and condensation of steam, or by making it act above and below the forcer of a piston, a lever is raised and depressed with any degree of power, from that of one horse to 300, every 19 cubic inches of water producing 20 feet of steam, which is equal in expansive force to the power of one horse, produced by less than a quarter of a pound of coal, with from 30 to 40 strokes per minute; and, in general, a chaldron of coal works 100 horse-power for four hours. Steam-engines are divided into low-pressure and high pressure; in the latter, the steam being excited by the heat of 212, that of boiling water, is recondensed by cold, and a valve provides for its escape, when it raises the thermometer above 30 inches. But if the valve is loaded with a second 15lb., equal to another atmosphere, then the mercury will rise to 60, and the force be doubled, steam being 20 times its former bulk; if it be loaded with 28 lbs. it will be again doubled, and so on ; but, of course, such augmentation of force tries the strength of the engine. Of course, the energy of the steam rises from the motion of the oxygon transferred to the combustible, and by it to the water, the atoms of which evolving, in consequence, form moving circles, and hence the expansive force. The boiler is on the right-hand, and communicates the steam to the piston O A, whence it rushes into X and G, and raises the rods X Q, and G C, which force up the beam; and the beam carries round a small wheel O, which works in the small one, S, connected with the large one, R, and with R the works are connected.