46 A VIS INERTIAS

qually easy to give the same degree of ce-lerity

" light, and the vibrations of the other are swifter,“ and as oft as they overtake the vibrations of the first," they put them into those fits. But how two Æthers“ can be diffused through all space, one of which acts" upon the other, and by consequence is re-acted up-“ on, without retarding, shattering, dispersing and“ confounding one another’s motions, is inconceiva-" ble.” If then it is inconceivable that the action ofthis medium should not be retarded, shattered, Uc. bythe re-action or resistance of another medium, thoughboth so rare and unresisting, as not to impede the mo-tions of the celestial bodies; is it less inconceivable thatits action should not be retarded, shattered, &c. beforeit reaches the heart of marble, brass, adamant ?

As to what Sir.//! Newton fays in the last part cited fromQuest. 2 1 . That the littleness of the repelling particlesmay contribute to the greatness of their repulsive force.This is a direct impossibility, unless he ascribes this re-pulsive force to an immediate immaterial power exerted,and not to the particles themselves; which argument Ishall insist upon, when I come to speak of the repulsiveforce of the particles of air, and of the cohesion of theleast parts of matter; for otherwise, it is as if we shouldfay, The less the adequate cause is (a repelling particle,to wit) the greater the effect may be (namely, the foresexerted by it). The less a material particle' is, the lesspower it must have, secluding all other agency; andthat can never produce the greater effect : nay (I-repeatit) it must be an immaterial agent; for the mechanicaction of other matter could never be greater on a par-2 tide