Page:A Letter on the Subject of the Cause (1797).djvu/53

 preſſure, before one breath can be diſcharged. And the re-action of this expanſive power, meeting the piſton of the Engine in its deſcent, and preſſing on the ſide contrary to that where the power of ſteam is acting, would immediately reſtore the balance and ſtop the machine; even was the friction of the whole annihilated.

I have only two more hints to trouble your Lordſhip with on this part of the ſubject, before I proceed to the Air-pump; the original inventor and applier of which to ſteam engines, was Mr. Wood of Shropſhire, who obtained the King’s Patent for it in the year 1759, and in the Specification annexed to ſaid Patent, uſes theſe words:—“The condenſed air muſt be pumped out by a pump to be worked by the motion of the Engine or any other way.” But to return,—the two points I propoſe to bring for your Lordſhip’s obſervation are,

Firſt; To admit the ſteam into the condenſer for the purpoſe deſcribed by Newcomen, would defeat the intended improvement, and even the action of the machine in toto. As before the condenſer could be heated to a degree ſufficient to allow the ſteam to expand, ſo as to force out the water and air, it muſt be ſo violent as to become