24 A rr^i/eo/BODIES. Chap. 3. 



Now that which deceived the authours of this opinion, was 

 that they had not a right intelligence of the caufes which made 

 little parts of bodies ( naturally heavie) defccnd flowly, in re- 

 gard of the velocitie of greater parts of the fame bodies deicend- 

 iag : the doctrine of which we intend to deliver hereafter. 

 , Others therefore perceiving this ride to fall fliort, have in- 



Tiie opinion of deavoured to piece it out by the mixtion of vacuitic among bo- 

 thoic Phiiofo- jjjgj . believing it is that which maketh one rarer then another. 



' 



rhcrs related, . 



Uho put rarity Which mixtion they do not put alwayes immediate to the 

 to eonfift in the nia j n ^ , ( , con fij cr . b ut jf j t nave O rh e r rarer and liohter 



mixtion or \a- i j i i v i- ... c . 



cuity among bodies mingled with it, they concerVe this mixtion imrnrnediate 

 oncly to the rareft, or lighted. As for example ; a cryftall be- 

 ing lighter and confequently rarer then a diamond, they will 

 not fay that there is more vacuity in a cryftall then in a dia- 

 mond; but that the pores of a cryftall are greater, and that con- 

 fequently there is more aire in a cryftall to fill the pores of it,' 

 then is in a diamond ; and the vacuities are in the aire, whicrr 

 abounding in a cryftall, more then in a diamond, maketh that 

 lighter and rarer then this, by the more vacuities that arc in 

 the greater Quantitie of aire which is mingled with it. 



Butagainft thisfuppofition, a powerfull adverfary is urged: 

 for Ariftotle, in his 4. book of Phyncks, hath demonstrated 

 that there can be no motion in vacuity. It is true, they indea- 

 vour to evade his demonftration ( as not reaching home to 

 their fijppofition ) by acknowledging it to be an evident one 

 in fuch a vacuity as he there fpeaketh of ; which he fuppofed 

 to be fo great a one that a bodie may (wimme in it as in an 

 ocean, and not touch or be near any other body .- whereas 

 this opinion cxcludeth all fuch raft inanitie, and admicteth no 

 vacuities but fo little ones as no body whatfocver can come un- 

 to but will be bigger then they; and confequently, muft on 

 fome fide or other touch the corporeall parts which thole va- 

 cuities divide;fbr they are the (eparacions of theleaft parts* that 

 are, or can be, actually divided from one another : which 

 parts muft of neccffitie touch one another on fbme fide ; or 

 elft they could no: hang together to compofe one fubftanccjond 

 therefore, the dividing vacuities, muft be JefTe then the divided 

 parts. And thu$, no bodic will ever be in danger of floating up 

 and down without touching any thing : which is the diffccultie 

 that Ariftotle chiefly irnpugncth. 1 



