Bodies affeSed by FriBion, . 167 



^dly, IVheiher the fridVion varies in proportiofi to the prejfure 

 ar weight, 



4thlv, Whether the JriBion be the fame on whichever of its fur- 

 faces a body moves. 



The experiments, in which I was affifled by my ingenious 

 friend the Rev. Mr. Jones, Fellow of Trinity College, were made 

 with the utmoll: care and attention, and the feveral refults 

 agreed fo very exa6ily with each other, that I do not fcrnple to 

 pronounce them to be conclufive. 



2. A plane was adjufted parallel to the horizon, at the extre- 

 mity of which was placed a pulley, which could be elevated or 

 deprefled in order to render the firing which connecled the 

 body and the moving force parallel to the plane. A fcale accu- 

 rately divided was placed by the fide of the pulley perpendi- 

 cular to the horizon, by the fide of which the moving force 

 defcended ; upon the fcale was placed a moveable flage, which 

 could be adjufled to the fjpace through which the moving force 

 defcended in any given time, which time was meafured by a 

 well regulated pendulum clock vibrating feconds. Every thing 

 being thus prepared, the following experiments were made to 

 afcertain the law of fridlon. But let me firfl obferve, that if 

 fri6lion be a uniform force, the difference between it and the 

 given force of the moving power mufl be alfo uniform, and 

 therefore the -moving body muft defcend with a uniformly ac- 

 Cfclexated velocity, and confequently the fpaces delcribed from 

 the beginning of the motion mufl be as the fquares of the 

 times, jufl as when there was no friction, only they will be 

 diminifhed on account of the fri£lion. 



3. Exp. I . A body was placed upon the horizontal plane, 

 and a moving force applied, which from repeated trials was found 

 to defcend 52! inckes in 4'^ for by the beat of the clock and 



7 the- 



