134 COEFFICIENTS OF INDUCTION. 



it follows that 



t)j> r 



Utilising, lastly, the known values 



we get 



I. 3 ...2+I 



' 



2 2.4 r^ 



+ ( ~ l)n 2.4. '.'.'(2* + 2) \rj " 2n + l 

 We may put 



In the plane of the layer in particular, where Q = - , we have 



2 



2.4... 2 r 



(3) X = 0, 



2.4 



