IO2 tATrcatifecf BODIES. Chap.io. 



comparifon of all them; not out of the confederation of any 

 one alone, rcfulteth the differences of their velocities : ( and that 

 neither, but in as much as concerneth the confidenuion of the 

 moveablcs: for ro make the calculation exaft, the medium muft 

 likewife be confidered ; as by and by wefhnll declare ) for fince 

 the motion dependeth of all them together ; although there 

 fhould be difference between the moveables in regard of one 

 oncly, and that the reft we're cquall ; yet the proportion of the 

 difference of their motions, murt not follow the proportion of 

 their difference in that one regard : becaufe their difference con- 

 fidered fingle in that regard will have one proportion; and with 

 the addition of the other confederations ( though alike in both ) 

 to their difference in this, they will have another. 



As for example, reckon the denfity of one moveable to be 

 jble the denfity of another moveable; Co that in that regard 

 /ath two degrees of power to defcend , whereas the other 

 hath but one : fuppofe then the other caufes of their defcent to 

 be alike jn both, and reckon them all three : and then joyn 

 theic three to the one which is caufed by the deniity in one of 

 the moveablcsjas likewife to the two, which is cat i fed by the 

 denhty in the other moveable : and you will find that thus al- 

 together, their difference of power to dclcend k no longer in a 

 double proportion ("as it would bc 3 if nothing but their denfity 

 were confidered ) but is in the proportion of five to fbure. 

 But after we have confidered all that concerneth the move- 

 ables, we are then to caft an eye upon the medium they are to 

 move in; and we fhall find the addition of that, to dccreafe 

 the prbportion of their difference, exceedingly more; according 

 to the ceflibility of the medium. Which if it be airc; the great 

 difproportion of its weight , to the weight of thofe bodies 

 Which rricn ufe to take in making experiences of their deicent 

 in that yielding medium; will caufe their difference of velo- 

 city in dcfcending, to be hardly perceptible. Even as the diffe- 

 rence of a fiiarp or dull knife, which is eafily perceived in 

 cutting of flefh or bread , is not to be diftinguifhed in divi- 

 ding of water or oyl. And likenife in weights, a pound and 

 a fcruple will bear down a dramme in no fcnfiblc propor- 

 tion of velocity more then a pound alone would do : and yft 

 put a pound in that fcale in ftcad of the dramme, and then 



the 



