CHAPTER II 

 RHYTHM 



THE third corollary from the persistence 

 of force may best be introduced by a 

 reconsideration of the simplest case of 

 motion contemplated by the preceding corol- 

 lary. The realization of Galileo's first law of 

 motion — the law that a moving body must for- 

 ever continue in a straight line with uniform 

 velocity — obviously postulates the non-exist- 

 ence of any other matter than that contained in 

 the body in question. If there were but one 

 body in the universe, that body, when once set 

 in motion, would never alter its direction, or 

 undergo any increase or diminution of velocity. 

 The introduction of a second body, attracting 

 the first and attracted by it, alters the result in 

 a way which now demands brief consideration. 

 If the motion with which the two bodies start 

 is such as would carry them along a straight 

 line toward each other, they must obviously 

 rush together, and the case is thus again re- 

 duced to that of a single moving body. But 

 this case is too simple to have been ever actually 

 realized. What we have to deal with is the 

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