Savery stated that this circumstance immediately suggested to him the possibility of giving effect to the atmospheric pressure by creating a vacuum in this manner. He thought that if, instead of exhausting the barrel of a pump by the usual laborious method of a piston and sucker, it was exhausted by first filling it with steam, and then condensing the same steam, the atmospheric pressure would force the water from the well into the pump-barrel, and into any vessel connected with it, provided that vessel were not more than about thirty-four feet above the elevation of the water in the well. He perceived also, that, having lifted the water to this height, he might use the elastic force of steam in the manner described by the Marquis of Worcester to raise the same water to a still greater elevation, and that the same steam which accomplished this mechanical effect would serve, by its subsequent condensation, to reproduce the vacuum, and draw up more water. It was on this principle that Savery constructed the first engine in which steam was ever brought into practical operation.
BRANCA'S ENGINE.
FOOTNOTES:
[1] Arago, Eloge historique de James Watt; p. 22.
[2] Ibid., p. 21. note.
[3] Farey, Treatise on the Steam Engine, p. 93.
[4] Arago, sur les Machines à Vapeur, Annuaire, 1829, p. 165
[5] Spiritus, breath or air.
[6] Exactly 15·68 oz. = 0·98 lb.