106 OH THE LAWS OF NATURE. 



which experience gives him to know, then muft he 

 judge, that the latter are accidental, or that they de- 

 pend on a particular will of the Sovereign Being. 



If, however * — and this is really the cafe — the laws 

 of ftatics and mechanics declared by experience agree 

 * with thofe which reafoning a priori difcovers to us, 

 then the conclusion is natural, that the obferved laws 

 are neceffary truths, therefore not dependent on the 

 arbitration or choice of any being. 



We then fee, that thefe laws refult of themfelves 

 from the exiftence of matter. 



Now, it is demonftrated, that a body left to itfelf 

 muft remain for ever in a ftate of reft or of uniform 

 motion — it is demonftrated, that, if fuch body in its 

 motion ftrive at once to follow the two lides of a 

 parallelogram, the diagonal is the direction which it 

 muft take of itfelf. It is demonftrated, that all laws of 

 imparting motion between bodies are reducible to the 

 laws of equilibrium, and that thefe latter are redu- 

 cible again to the laws of equilibrium of two like bo- 

 dies, which with like virtual velocities are tending in 

 oppolite directions. 



In the latter cafe, the motions of the two bodies 

 muft manifeftly mutually difplace each other. By ge- 

 ometrical neceflity then there will ftill be an equilibri- 

 um, if the maffes are in a converle ratio of the velo- 

 cities. 



It ftill remains to be known, whether the cafe of 

 equilibrium is iingle, i. e. whether, if the maffes be 

 not in converfe ratio of velocities, the one body muft 



neceffarily fet the other in motion ? 



It 



