Page:A Letter on the Subject of the Cause (1797).djvu/57

 at a loſs to judge the cauſe of this declenſion, and on this account I ſhall be more plain on the ſubject. Much pains were taken on this Trial to convince the Court, that proportion, lateral and altitudal ſituation, did not at all, or not eſſentially ſignify; I will therefore confine what I have to ſay more directly to theſe points; with a ſmall digreſſion only to conſider, as in the caſe of Mr. Gitty, ſome remarks, from the eminent and ingenious Mr. Cummings, reſpecting this important article.

My experience, my Lord, obliges me to allow, that when a pump is introduced, or added to one of Newcomen’s Engines where there is no condenſer, a trifling latitude in the ſize, over and above the real maximum, is of little moment, and may be exerciſed without much detriment to the Engine; but I find the cloſer we adhere to the ſmalleſt that is ſufficient, the leſs the power of the Engine is impeded by giving it motion.

As the actual proportion the pump ought to bear to the cylinder, muſt be the reſult of duly conſidering the Engine both in a perfect and leſs perfect air-tight ſtate, I will leave every Engineer to ſtudy for himſelf as Mr. Watt has done; and haſten to give my reaſons why pumps