Page:A Letter on the Subject of the Cause (1797).djvu/48

 is impracticable; and that no Engine can be built with a condenſer and without an air-pump, any thing like ſo good as Newcomen’s. And will likewiſe affirm, my Lord, and ſtate it as an immutable poſition, that by taking away this pump which extracts the condenſed water, and uncondenſed vapour, from the beſt Engine ever built by Meſſ. Bolton and Watt, the motion could not be continued one minute with a force ſufficient to carry her vis inertiæ, although the reſiſtance of the work ſhould be detached at the inſtant the action of the pump was ſuſpended.

And further, that all the ingenuity of the inventor himſelf, aſſiſted by thoſe able allies he had at his outſetting, could not by any device they were, or are maſters of, make this Engine work under theſe circumſtances, by diſcharging the water and vapour out of the condenſer by the eduction pipe Newcomen adopted. For in the Engine of Newcomen, when the ſteam re-enters the cylinder under the piſton ſo as to balance the outer or circumambient air, the water is diſcharged through the eduction pipe by its own gravity: bur the air or uncondenſed vapour would unavoidably remain, was it not for another cauſe, (which I ſhall hereafter prove cannot be applied in a condenſer) namely, the application of a valve called