k 



PHYSICAL AND LITERARY. loi 



what is gained by the other ; the whole 

 cffe«5l or change, with regard to motion, 

 being the fame as if it had been inftan- 

 taneoufly produced. And there is no ar-» 

 gument to be drawn from hence, to prove 

 jthe adive refiftance of one body at reft 

 ICO another in motion, or the tendency of 

 any body in paotion to return to a ftate 

 of reft. 



From the experiment of Mr Poleni we 

 learn, that fpheres of equal diameters 

 falling upon foft clay, make equal im- 

 preflions, when the produdls of the quan- 

 tities of matter into the heights from 

 which they fall are equal ; that is, when 

 the quantities of matter multiplied by 

 the fquares of the velocities are equal. 

 As it is much eafier to determine when 

 two impreflions are equal, than when 

 they differ in any proportion of magni- 

 tude, the velocities of the different bo- 

 dies in this experiment are fo adjufled, 

 in refped of the quantities of matter, as 

 that the impreflions may be equal. But, 

 from thence we conclude, that fuch im- 

 preflions 



