C i6 s 3 
X. On the Motion of Bodies affected by .Friction. By the Rev* 
Samuel Vince, A. M. of Cambridge ; communicated by 
Anthony Shepherd, D. D. F . R. S. F hum an Profeffor of 
Afronomy and experimental Philofophy at Cambridge. 
Read November 25 j 1784.. 
T HE fubjedt of the paper which I have now the honour 
of prefenting to the Royal Society, feems to be of a 
very confiderable 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 fridtion of bodies in motion 
upon each other will enable him at fir 11 to render his machines 
more perfedt, and fave him in a great meafure the trouble of 
corredting them by trials;, and to the latter, as thofe laws 
will furnifh him with principles for his theory, which when 
eftablifhed 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 fubjedt may conftitute, 
and however, from its obvious ufes, it might have been ex^ 
pedted 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 molt 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 final! velocities the fridtion varies 
very nearly as the velocity, but that in great velocities the fridtion 
increafes ; he has alfo attempted to prove, that by increafing 
2 the 
