Chap. 9. A TrtAlifc of BODIES. S 



powerfully overcome the refiftance ; and confcquently , en- 

 crcafe the velocity of che motion , in the fame propor- 

 tion as they flock thither ; until 1 it attain that degree of 

 velocity, which is the utmoft period that the power, which the 

 Agent hath to overcome the refiftance of the medium can bring 

 h ielfun to. Between which and reft, or any other inferiour de- 

 gree of vclocitie, there may be defigned infinite intermediate de- 

 grees, proportionable to the infinite divisibility of time, and 

 fpacc,in which the mover doth move. Which degrees doarifc 

 out of the reciprocal! yielding of the medium. And that is hke- 

 Wiiedivifiblein the lame infinite proportion. 



Since then, the power of all naturall Agents is limited j the 

 mover (be it never fo powerfull) mud be confined to obfervc 

 thcfe proportions ; and cannot pafle over all thefe infinite de- 

 fignablc degrees in an inftant; but rnuft allot fcxnc time (which 

 hath a like infinity of dcfignable parts) to ballance this infinity 

 of degrees of velocity: audio confequently, it requircth time, to 

 attain unto any determinate degree. And therefore cannot re- 

 cede immediately from reft unto any degree of celerityjbut muft 

 necefTarily paflc through all the intermediate ones. 



Thus it is evident that all motion which hath a beginning 

 muft of neccflity incrcafe for fomc time. And fince the works of 

 nature are in proportion to their causes, it followeth that this 

 cnci'calc is in a dererminate proportion. Which Galilcus (unto 

 whom we owe the greateft part of what is known concerning 

 motion)teacheth us how to find out ; and to discover whit de- 

 gree of celerity any moveable that is moved by nature, hath in 

 any determinate part ofthefpace it moveth in. 



Having fettled thefe conditions of motion; we (hall do well in 

 the next place to enquire after the caufes ofit:as well in the body -rj,t coLitiow 

 moved, as alfb in the mover thatoccafioncth the motion. And whi = h h dp ( t( * 

 bccaufe we have already fhewed, that locall motion is nothing moveahic'ar^ 

 in fubft-aice but divifionrwc may determine that thofcciufcs w ch thr jin tlii; 

 contribute to divifion^or rcfift it are the caufcswhich make or re- 

 fill locall motion.Ithath alfo been faid, that Denfity hath in it a 

 power of dividing-and thatRarity is the caufc of being divided; 

 lik wife we have faid that fire by reafonofks fmal partSjiaro w ck 

 it may be cutfwhich maketh them fharp) hath alfo an eminrnce 

 in dividing: fo that we have two qualities, denfity and tenuity 



F or 



