3 8

Sir Isaac Newton’s

Book I.

18. Now this experience is alone fufficient to fhew to usthe whole of this law of motion.

19. S1 n c e we find, that the fame power will always pro-duce the fame change in the motion of any body, whetherthat body were before moving with a fwifter or flower mo-tion ; the change wrought in the motion of a body dependsonly on the power applied to it, without any regard to thebody’s former motion: and therefore the degree of motion,which the body already pofiefles, having no influence on thepower applied to difturb its operation, the effects of thefame power will not only be the fame in all degrees of mo-tion of the body ; but we have likewife no reafon to doubt,but that a body perfectly at reft would receive from any pow-er as much motion, as would be equivalent to the effecft of thefame power applied to that body already in motion.

10. Again, fuppofe a body being at reft, any number ofequal powers fhould be fucceflively applied to it; pufhing itforward from time to time in the fame courfe or direction.Upon the application of the firft power the body would beginto move; when the fecond power was applied, it appears fromwhat has been faid, that the motion of the body would be-come double; the third power would treble the motion of thebody; and fo on, till after the operation of the laft power themotion of the body would be as many times the motion,which the firft power gave it, as there are powers in number.And the effed of this number of powers will be always the

fame,