174 Mr. C. S. Whitehead on the Effect of a Solid 

 Therefore V — ye Zpt to, 



dV .dto 



U= — -j- = —yen* ~r . 

 dr dr 



Now to = 2tt J 1- cos * + X, S} ~ L (0 W ?»'(«) ?n(0) 1 . 



r £ c. 



P„ is the zonal harmonic of the n th order, and 



dP n 

 P n ' = -7— /* = cos 0. 



.: U— h>S^(£}*P.'MP.W). 



In the dielectric magnetic induction is the same thing as 

 magnetic force. 



Therefore, from the second equation of (9) 



to n =-2^ 7 ^Q n p n '(a)P n (d)- 

 Therefore 



dto n sin 2 a sin0 /r\* p ,, „ , a 



Therefore, when k& is large, 



Bl ._H,s[i-e)^(i-^B)] 



x ^0 P«'(«)P (l ^)cos(^-U; • . (15) 



m rv °° T, ?l /a\ 2 " + 7l /*(2W + 1)\"1 



T,-*7 2 [l + — x ( ; ) (1 - ^j-^ 



x! i^ ^(0P.- W p; W co. (,* + *.). . . (16) 



if ds = rdd. 



If r is but little greater than a, 



tan£ w =l, therefore £ = j approximately; 



tan</> n = 0, therefore </>h = approximately. 



