STEAM ENGINE use of fire for forging metals, heating water, making bread and the like was known at a very early day in history (Gen. iv. 22; xviii. 6), but we have no knowledge as to the time when this serviceable element was discovered. " Probably it was one of man's very earliest acquisitions, being the agent he has most constantly employed in the preparation of his food. Flints have been found that have been sub jected to the fire for the purpose of breaking them into small and angular pieces, and the charcoal and ashes of ancient hearths have been exhumed in deposits which competent geologists place as remote in time as the Interglacial period." Implements of bronze have come down to us from prehistoric times, and these also give evidence of the very early use of fire. But its employment for converting water into steam for prac tical purposes is of comparatively recent date.
Hero's first recorded instrument for illustrating the power of steam was that described by Hero of Alexandria in his Pizeu .mafica about 120 I3. C., though there is nothing in the text to indicate that it was his invention. It was named the " zeolipile" (61. So, fig. I), and consisted of a boiler partly filled with water and placed over a fire. Over the boiler there was pivoted on two bent tubes a spherical vessel (" steam-turbine") which was supplied with steam through one of the pivots from the boiler below. Projecting from the sphere in a direction perpendicular to the axis of rotation were two bent pipes, through which the steam escaping into the air exerted a force in a contrary direction, after the manner of Barker's mill (p. 37), thus causing the sphere to revolve. It is not known that the was ever more than an amus ing toy, though some have supposed that it was applied by the Greek priests for producing motion of apparatus in their temples.
Further trace of the force of steam is lost in history until the time of Justinian (A. D. 554), when it was employed by Anthemius, architect to the emperor, to frighten his neighbor Zeno, by connecting tubes to the cauldrons of water and extending them up into the building, so that when the steam ascended the house was shaken by the escape of the impris oned air. Alberti, the Florentine architect, notices (A. D. 1412) the pro
digious expansion by heat of water shut up in the cavities of some stones, " which blows up the whole kiln with a force altogether irresistible." If the statement of Spanish writers that Blanco de Garay, A. D. 1543, applied steam to the propulsion of a ship at Barcelona, is apocryphal, as the majority of writers on the subject believe it to be, there was made from the time of Hero to the seventeenth century no practical application of the power of steam worthy of special illustration. Here and there are found evidences of a knowledge of its force in its employment for trivial purposes, such as blowing organs and turning spits, but it devolved on a later period to demonstrate its power in its application to the performance of important and useful work.
John Mall esins (1567) hinted the construction of a machine in which "the volcanic force of a little confined vapor might be made to perform the work of horses or water." The " Pneumatics of !hero" were in 1587 translated into the Italian, tvhieli drew attention to the "ingenious toys," as they have been called, in which "air" was applied with great skill to produce motion. Sir lIugh Plat describes (1591) the construction of "a rounde ball of copper or kitten that will blowe the fire very stronglie by the attenuation of water into airs." Porta's r6oi, Giovanni Battista delta Porta, in a treatise on pneumatics, described an apparatus for raising a column of water by the pressure of steam. Figure 2 (p. 8o), from Porta's book, shows the furnace surmounted by a boiler, above which is a tank nearly filled with water. As the steam from the boiler enters the tank near the top, the water is driven out through the curved pipe.