122] 



POLAEIZED DISTRIBUTIONS. 



233 



But if h is infinitesimal, we have, neglecting infinitesimals of 

 the second order, r 2 r^ = h cos (hr) and r^ 2 = r 2 , 



.p _ mh cos (^r) _ M ,, , 

 r* ~ ~r* OS ^ r ^* 



(5) 



Now in a polarized body in general, the element of volume 

 dadbdc contributes the potential 



Idadbdc cos (Ir) _Ir.dr 

 ;ff ,* ' 



so that we obtain the form already given. 



If the direction of the axis of the doublet is that of the 

 JZ-axis, we have 



to which, by 103 (10), we find the conjugate function 



qy _ _ Mp* == 

 r 3 



FIG. 53. 



