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X. On the Motion of Bodies affecled by FrlBion. By the Rev. 

 Samuel Vince, yf. M. of Cambridge; CGmmtmicated by 

 Anthony Shepherd, D. D. F, R. S. Plumia?2 Profejfor of 

 Ajlronotny and experimental Philofophy at Cambridge. 



. Read November 25, 1784, 



THE fubje6l of the paper which I have now the honour 

 of prefentlng to the Royal Society, feems to be of a 

 very confiderable importance both to the practical mechanic 

 an4 to the fpeculatlve philofopher ; to the former, as a know- 

 ledge of the laws and quantity of the fri6llon of bodies in motion 

 upon each other will enable him at firft to render his machines 

 miore perfect, and fave him in a great meafure the trouble of 

 corre£ling them by trials ; and to the latter, as thofe laws 

 will furnifli him with principles for his theory, which when 

 eflablifhed by experiments will render his conclufions appli- 

 cable to the real motion of bodies upon each other. But, how- 

 ever important a part of mechanics this fubje^l may conflitute, 

 and however, from its obvious ufes, it might have been ex- 

 pe6led to have claimed a very confiderable attention both from 

 the mechanic and philofopher, yet it has, of all the other parts 

 of this branch of natural philofophy, been the mod neglected. 

 The law by which the motions of bodies are retarded by fric- 

 tion has never, that I know of, been truly eftabiilhed^ 

 MusscHENBROEK fays, that in fmall velocities the fridion varies 

 very nearly as the velocity, but that in great velocities the fri£lion 

 .increafes ; he has alfo attempted to prove, that by Increafing 

 Z the 



