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X. On the Motion of Bodies affedied by FnSlion. By the Rev, 

 Samuel Vince, A. M. of Cambridge ; CGinmunicated by 

 Anthony Shepherd, T). D. F» R. S. Plumian Profejfor cf 

 Afironomy and experimental Philofophy at Cambridge. 



Read November 25, i78'4». 



THE fubjed of the paper which I have now the honour 

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

 very conliderable importance both to the practical mechanic 

 and to the fpeculative philofopher ;. to the former, as a know- 

 ledge of the laws and quantity of the fri6tion of bodies in motion 

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

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

 correcting them by trials; and to the latter, as thofe laws 

 will fnrnifh him with principles for his theory, which when 

 eftablidied 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 fubjeCl may conftitute, 

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

 pelled to have claimed a very conliderable attention both from 

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

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

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

 tion has never, that I know of, been truly eftablifhed. 

 MusscHENBROEK fays, that in fmall velocities the friftion varies 

 very nearly as the velocity, but that in great velocities the fridioii 

 increafes ; he has alfo attempted to prove, that by increafing 

 2 the 



