PHYSICAL AND LITERARY. 33 



grade motion, the vires inftta of the two 

 bodies muft carry them on in the fame 

 diredion, which is contrary to fadl. It 

 is obvious, then, that there can be no re- 

 percuffion or reaction of the body at reft. 

 All the obftrudion it gives to the adlion 

 of the impinging body, muft be merely 

 by rellftance. The other point to be fet- 

 tled is, whether the operation be inftanta- 

 neous, or whether it be performed in 

 time? That it is inftantaneous, will thus 

 appear. A gradual change of motion 

 iuppofes, that the foremoft body pafTes 

 through every degree of velocity from reft 

 till it acquires its greateft velocity ; and 

 that the motion of the impinging body 

 is gradually retarded in proportion. But 

 this fuppofition is inconfiftent with a 

 known fa6l, that the bodies continue con- 

 joined after contacft ; whence it is evident, 

 that both muft move with the fame velo- 

 city from the inftant of contadl. 



Thes£ preliminary points being fet- 

 tled, the operation may be eafily analy- 

 fed. Tho' the whole is performed in an 

 inftant, it may, however, be diftinguiflit- 

 YoL. I. E ed 



