I "o M'\ V J NCE on the Mouon of 



4, Mavliig proved that the retarding force of all hard bodies 

 ariiing trom trittion is luiiform, tlie quantity of fridion, con- 

 fidered as equivalent to a weight without inertia drawing the 

 body on the horizontal plane backwards, or a<fling contrary to 

 the moving force, may be immediately deduced from the fore- 

 going experiments. For let M = the moving force expreffed by 

 its weight; Fi=the fricflion ; W=rthe weight of the body 

 upon the iiorizontal plane; S = the fpace through which the 

 moving force defcended in the time t expreHed in fecotids ; 

 r=i6-j-a feet; then the whole acceitrative force (the force of 



gravity being unity) will be ^^ 7" y hence, by the laws of uni* 

 formly accelerated motions, ■ , - x rr — S, confequently 



F — M — - ^ "^ . z^ . To exemplify this, let us take the cafe of the 



laft experiment, where Mz=7, Wr: 25I, 5=4/^ feet, i^^^'i 



hence F= 7 -^^4^7^ = 6.417 ; confequently the fridion was 



to the weight of the rubbing body as 6.4167 to 25.75. ^'^^ 

 the great accuracy of determining the friction by this method is 

 manifefl: from hence, that if an error of t inch had been made 

 in the defcent (and experiments carefully made may always de- 

 termine the fpace to a much greater exadnefs) it would not 

 have affeded the conclufion -^;-o-dth part of the whole. 



5. We come in the next place to determine, whether fric- 

 tion, cceteris paribus, varies in proportion to the weight or 

 preflure. Now if the whole quantity of the fridion of a body, 

 meafured by a weight without Inertia equivalent to the fridion 

 drawing the body backwards, increafes in proportion to its 

 weight, it is manifefl:, that the retardation of the velocity of 

 the body arifing from the fridion will not be altered; for the 

 7 retardation 



