406 NEW INVESTIGATION OF 



excepting those points situated in lines passing 

 through P and parallel respectively to Xy 3/, & z. 



2 refers to all the other points of the system. 



Then we have -~ = the attraction of P, on P 



in the direction of PjP, where p is a constant and 

 equal to P/s amount of attraction at a unit of 

 distance from P. 



The cosines of the angles which P,P makes 

 with the axis of x, y, z respectively will be ' 



— —\ — — (See Poisson's Mecanique, p. 171.) 



Hence, if we resolve —2 parallel to the co- 

 ordinate axis by multiplying it by the cosines of 

 the angles which it makes with the co-ordinate 

 planes we shall have — 



1— — 3-^ = force parallel to the axis of x 

 S-e(^= do. do. !/}{\) 



j..P(iz£!) = do. do. 



