Chap. I?. 4 Trtatifeof BODIES. 



hand, and from above downwards, when itc.imc fro;n A to B. 

 And consequently , ic muft in cquall time have palled another 

 line from left hand to righc hand, as long as the line C U; and 

 likcwifc, it muft at the ! a me time have paHed another line from 

 below upwards as long as A C : \vnich vvill of nccefficy make 

 it hit in the point F, at the end of fo much more time as ic .'pent 

 in going from A to B; and To, make the two angles ABC and 

 FB E equall ; as every one knowcch that hath biufilu:cd Eu- 

 clide. 



The motion which we call undulation ncedeth no further ei- 

 plication: for it is manifeft, that fince a pendant, when it is re- Tilc 

 moved from its perpendicular, will reftore it felf thereunto by 

 the naturall force of gravity, and that in fo doing ic giineth a 

 velocity, ( and therefore cannot ceafc on a fuddain, _) it muft 

 needs be carried, out of the force of that morion, dircdlly the 

 contrary way: untill the force of gravity, overcoming the ve- 

 locity it muft be brought back again to the perpendicular: which 

 being done likewife with velocity, it muft fend it again towards 

 the place from which it fell at the firft. And in this courfe of 

 motion it muft continue for a while, every undulation being 

 weaker then other untill at laft it quite ceafeth, by the courfe of 

 nature fettling the aire in its due fituation according to the na- 

 turall caufes that work upon it. And in this very manner alfo 

 is performed that undulation which tvc fee in water, when it is 

 ftirred from the naturall fituation of its fphericall fuperficics. 



Galileo hath noted that the time in which the undulations 

 are made which follow one another of their own accord, is the 

 fame in every one of them ; and that as much time precifely is 

 taken up in a pendants going a very fhort arch towards the end 

 of its vibration, ss was in its going of the greareft arch at the 

 beginning of its motion. The rcafon whereof feern:t!i ftrange to 

 him, and he thinketh it to be an accident naturall to the body 

 'out of its gravity; and that this effcft convinccth, it is not the 

 aire which moveth fuch bodies. Whereas in truth, it is clearly 

 the aire which caufeth this effect. Becatife the aire ftriving at 

 each end ( where it is furthcft from the force of the motion ) to 

 quiet it felfjgetteth at every bout fomewbat upon the fpacej and 

 fo contra&eth that into a fhorter arch. 



But it is a great wonder to me, that Galileo fliould make a 



I 3 wonder 



