INTRODUCTION. 



\Vc shall have occn after to assume what may 



be called the converge of the principle of tin taasmiasibility <>t 



force, nani' ly. that if a force can be tra I'mm its point 



a second point without alt. -rin^ its . 

 ^econd point must be in the direction <-i the I 



17. 



hen we find it useful to change the point of applica- 

 tion of a force, we shall for shortness not always state that tlu> 

 new point is invariably connected with the old point, but this 

 must be always understood. 



