The description of the engine formerly mentioned is transcribed from Mr. Savery’s publication, “The Miner’s Friend,” and which had a subsidiary boiler, with water of a boiling heat, always ready to supply the large boiler; and the power of steam raised in it is employed to force the water into the larger boiler, to replace the waste occasioned by evaporation from that boiler; by this means the transposition of the feeding water is not only speedily performed, but being itself of a boiling heat, it is instantly ready to produce steam for carrying on the work. There is also one more grand improvement in the modern machine: the first engine was worked by four separate cocks, which the operator was compelled to turn separately at every change of stroke; if he turned them wrong, he was not only liable to damage the engine, but he prevented its effect, and, at the same time, lost a part of the operation: whereas, in the improved engine, the communications are made by a double sliding valve, or, as it has since been termed, regulator; that is, a brass plate, shaped like a fan, and moving on a centre within the boiler, so as to slide horizontally in contact with the under surface of the cover of the boiler, to which it is accurately fitted by grinding, and thus, at pleasure, opens or shuts the orifices, or entries, to the steam pipes of the two receivers alternately. This regulator acts with less friction than a cock of equal bore, and, by the motion of a single handle backwards, at once opens the proper steam pipe from one receiver, and closes that which belongs to the other receiver. Captain Savery, in his publication before noticed, describes the uses to which this machine may be applied, besides those before described, viz.--1, to serve water for turning all sorts of mills; 2, for supplying palaces, noblemen and gentlemen’s houses with water, and affording the means for extinguishing fires therein, by the water so raised; 3, the supplying cities and towns with water; 4, draining fens and marshes; 5, for ships; 6, for draining mines of water; and 7, for preventing damps in mines.