Page:Lettersconcerni01conggoog.djvu/165

140 Forces; conequently 'tis impoible there hould be any other Principle.

me Leave once more to introduce Sir Iaac peaking: Shall he not be allow'd to ay, My Cae and that of the Ancients is very different. Thee aw, for Intance, Water acend in Pumps, and aid, the Water ries becaue it abhors a Vacuum. But with regard to my elf, I am in the Cae of a Man who hould have firt oberv'd that Water acends in Pumps, but hould leave others to explain the Caue of this Effect. The Anatomit who firt declar'd, that the Motion of the Arm is owing to the Contraction of the Mucles, taught Mankind an indiputable Truth; but are they lee oblig'd to him becaue he did not know the Reaon why the Mucles contract? The Caue of the Elaticity of the Air is unknown, but he who firt dicover'd this Spring perform'd a very ignal Service to natural Philoophy. The Spring that I dicover'd was more hidden and more univeral, and for that very Reaon Mankind ought to thank me