STEAM-ENGINE. Steam-engines, in their infancy, were known as "fire" (that is, heat) engines;. and in point of fact thi older term is the more correct, because the water or steam is only used as a convenient medium through which the form of energy which we call heat is made to perform the required mechanical operations. In modern engines sufficient heat is added to the steam to raise it to a very high pressure, and the excess of this pressure over the pressure opposed to it (either atmospheric pressure , or the still lower pressure in a condenser) is both the cause and measure of the work done by the engine. In earlier machines, however, the steam was raised only to atmospheric press ure, and admitted into the engine only to be at once condensed by a jet of cold water. The excess of the atmospheric pressure above the preSsure in the partial vacuum caused by the condensation was then the direct cause of work. Engines of this kind are not now used; they were called atmospheric engines. As a source of power steam has many advantages over wind and water. It is independent of the weather, may be applied any where, affords a constant equable motion, and is capable of indefinite increase. Its invention, therefore, has caused a new era in the arts; and the revolution which it ban brought about in industry of all kinds, as,well as the influence it has had on civilization in general, and must yet have in a higher degree, are altogether incalculable.
The invention of steam as a moving power is claimed by various nations; but the first extensive employment of it, and most of le improvements made upon•the steam-engine, the world indisputably owes to the English and the Americans. It would appear that as early as 1543 a Spanish captain, named Blasco de Gamy, showed in the harbor .of Barcelona a steamboat of his own invention. It is most likely that Blasco's engine was on the principle of the ./Bolipile of Hero, invented 130 D.C., in which steam produces rotatory motion by issuing from orifices, as water does in Barker's mill (q.v.). The preacher Mathesius, in his sermon to miners (Nuremberg. 1562), prays for a man who "raises water by fire and air," showing the early application of steam-power in Germany; and the German engineer, Sol. de Cans, in the service of the elector palatine in Heidel
berg, describes, in his work. Les liaisons des Forces illouvantes avec Diverses Machines (Frankf. 1615), a steam-machine, which was merely a contrivance for forcing the water contained in a copper ball through a tube by applying heat. An Italian engineer. G. Branca, invented, in 1629, a sort of steam windmill; the steam being generated in a boiler, was directed by a spout against the flat vanes of a wheel, which was thus set in motion.
In England, among the first notices we have of the idea of employing steam as a pro pelling force, is that contained in a small volume.* published in 1647, entitled The Art of Gunnery, by Nat. Nye, mathematician ; in which he proposes to "charge a piece of ordnance without gunpowder," by putting water instead of powder, ramming down au air-tight plug of wood, and then the shot, and applying a fire to the breech "till it burst out suddenly." But the first successful effort was that of the marquis of Worcester. In his Century of Inventions, the manuscript of which dates from 1655, he describes a steam apparatus by which he raised a column of water to the height of 40 feet. This, under the name of " fire-waterwork," appears actually to have been at work at Vauxhall in 1656. Sir Samuel Morland in 1683 submitted to Louis XIV. a project 'for raising water hy means of steam, accompanying it with ingenious calculations and tables. The first patent for the application of steam-power to various kinds of machines was taken out in 1695 by rapt. Savory. In 1699 he exhibited before the Royal society a working model of his invention. His engines were the first used to any extent in industrial operations; they seem to have been employed for some years in the drainage of mines in Cornwall and Devonshire. The essential improvement in them over the older ones was the use of a boiler separate from the vessel in which the steam did its work. One vessel, in all former engines, had served both purposes. He. made use of the condensation of steam in a close vessel to produce a vacuum, and thus raise the water to a certain height, after which the elasticity of steam pressing upon its surface was made to raise it still further in a second vessel.