The first person we find in the records of antiquity now open to us as an experimentalist upon steam, is Heito the Elder, the son of a Greek, settled at Alexandria, who flourished about 130 years before the Christian era. In his work entitled Spiritalia, he describes, among other ingenious machines, three modes in which steam might be employed as a mechanical power :—to raise water by its elasticity ; to elevate a weight by its expansive force ; and to pro duce a rotatory motion by its reaction on the atmosphere. Toy-like as they appear, they deserve illustration.
Fig. 1. On the lid of the box, or cistern a, containing water, Hero placed a globe c, also partly so filled ; a pipe e rises from the cistern into the globe. Another pipe i pro ceeds from the globe, terminating over a vase as, and the vase itself communicates with the cistern by a pipe n. When the sun-beams fall on the globe, they heat the water, and raise vapour; this, by its expan sion, forces the water through the syphon i, which, trickling into the vase is again conducted by the pipe n, placed within it, into the cistern. When the-sun-beams are withdrawn, and the surface of the globe cooled by the surrounding air, the vapour within is condensed, and, by this means, a void is left in its upper part : the pressure of the atmosphere now forces the water in the cistern up the pipe e, to replenish it ; and the same operation of forcing water commences, when the sun s rays, falling on the sur face of the globe again, heat its contents. Here, almost under any circum stances, the effect could have been but trifling ; but in the second, Fig. 2, where we neat from a lamp or fire is substituted in the place of that from the sun, the power would not only be more available, but less hypothetical. A caldron a has a pipe c, (arising from its lid) shaped at its upper end cup-wise, for holding the ball or hollow sphere o. A fire being made under the caldron, the steam rising from the water which it contains flows through the pipe, and Ms up the ball placed in i to a height proportioned to the force of the steam! Fig. 3 shows the mode by which a small globe is made to revolve on its axis. Two pipes, a c, each having its upper extremity bent towards the other, rise from the cover of the caldron o ; one of these, o, acts merely as a pivot. the other, a, conducts steam, raised in the boiler, into the hollow globe i. This is suspended between them by having the steam-pipe a inserted into it, and is kept in its position by the pivot formed at the end of the opposite pipe c. Two hollow pipes a, also bent at right angles at their extremities, are inserted at the circumference of the globe, and form a communication between the caldron and the atmosphere. Heat being applied to the bottom of the caldron,
the steam issuing through the vertical pipe a into the globe i thence finds an exit ftom the arms a, and, by the reaction of the air, makes the lobe revolve on its axis with great celerity, "as if it were animated from within by a living spirit." Here, then, do we find the two properties of steam, expansion and contrac tion, recognised and applied almost two thousand years previously to the time of their being availed of for any efficient purpose. Scientific baubles, to be sure, were these contrivances ; but in them we have she undoubted germs of the vast and extensive power which its present modification permits. Hero, in his Introduction, professes to have made himself acquainted with the works of his predecessors and contemporaries, end, admiring their simple ingenuity, and unwilling that such fine inventions should perish or be overlooked, describes them, that they may be better and more generally understood. So that these very properties of steam may have been, and probably were known long prior to the time in which he flourished.
The next attempt of which history apprises us, to reduce steam to an agent of power, is described in a work by SoLomori DE Caus, an eminent French mathematician and engineer, published in 1615, entitled, Lei Raison des Forces mouvantes avec divers Dement de Fontaine. The following descrip tion will explain the principle of his device.
The caldron a is furnished with two pipes, b e, the latter of which reaches nearly down to the bottom of a. The pipe b is furnished with a cock d and funnel c. The vessel being nearly filled with water, and the cock d shut, fire is applied, as in Hero's vessel Fig. 2, and the steam, pressing on the surface of the water, forces up the lowermost portion through the tube e to a height propor tioned to its temperature. This is, cer tainly, another step in advance ; but without wishing to disparage the inge nuity of De Caus, it may be doubted whether the notion is really his own ; for in his dedicatory address to the French king, he invites His Majesty's especial attention, not so much to effect produced by this operation of the steam, as to his happy device of increaqing the sun's influence on his apparatus by the intervention of the lens—a charcoal fire being far too simple an affitir to catch his regards. He was well aware that the steam generated from boiling water became condensed into its pristine state of water on'being cooled, and juste ment Is mesme quantitil;" but the know ledge of this fact appears to have provoked no further speculation in his mind.