A Trtatip of B O D I E S. Chap, i o . 

 CHAP. X. 



Of (jravitj und, Levitj; and of Loeull Alotiw, commonly 

 termed, "tytturalf. 



I. IT is now time to confidcr that cfiftiaclion of motions which 



: motio 

 arc called na. 



I 



e motioni f ' K f o famous in Ariftotle; to wifj chat fbme motions arc natu- 

 turaii which rail, others violent: and to determine what may be Signified by 

 r k efe terms- F r fc ein g w * have faid that no body hath a nitu- 

 rail imrinfecall inclination unto any place , to which it is able 

 to mo ^ c i ^5 wc mu ^ Dce ^ s conclude that the motion of every 

 body followeth the percuiHon of extrinfecall Agents. It feem- 

 eth therefore impoffible that anybody fhouldhave any motion 

 naturall to it fclf. And if there be none natural!, there can be 

 none violent. And fothis diftinionwiil vanifh co nothing. 



O 



But on the other fide, living creatures do manifeftly fhew na- 

 turall motions, having naturall inftruments to perform certain 

 motions: wherefore fuch motions muft of necciTity be naturall 

 to them. But thcfc are not the motions which we are to fpeak 

 of; for Ariftotles divifion is common to all bodies, or at the 

 Icaft to all thofc we converfe withall : and particularly to thoic 

 which are called heavy and lightjwhich two terms paffe through 

 aH the bodies we have notice of. 



Therefore proceeding upon our grounds before layed; to 

 \vit, that no body can be moved of it felf; we may determine 

 thofe motions to be naturall unto bodies which have conftant 

 caufes, or percutients to make them altvayes in fuch bodies : 

 and thofe violent which arc contrary to fuch naturall moti- 

 ons. Which being fuppofcd , we muft fearch out the caufes 

 that fbconftantly make fbmc bod ies defccnd towards the cen- 

 ter or middle of the earth ; and others to rife and go from 

 the center: by which the world is fubjeft to thofe reftlefTe mo- 

 tions, that keep all things in perpctuall flux, in this changing 

 fphere of aftion and paffion. 



2. Let us then begin with confidering what cffe&s the funne 



oi (which i$ a conftant and perpctuall caufe ) workcth upon 

 Tpcraonofthe iafcriour bodies, by his being regularly fbmetimes prefent 

 funne, is the ar)( j fometimes abfent. Obfcrve in a pot of water hanffin* 



making and rai- r , . 



fingofatomes. over a nre, how the heat maketh fome parts of the water 

 to afcend, and others to fupply the room by defending, fo 



that 



