of Electrical Conductivities. 89 



Since 



idte~®=te~^—2yU(Z)+ const., 



this expression is 



in which C denotes a quantity independent of X, and for n its 

 absolute value may constantly be put. The value of C is 

 ascertained when the same term is calculated after replacing 



it thereby becomes 



or 



_G_ _4~ 1_ _ " (2l ' +1)2 IT 



abk7r 2Z (2v+iy e 

 By putting \=0 and remembering that 



2- 



7T 



(2i/ + l) 2 4 

 we get 



0= — — • 



abk 



Of surpassing importance for the investigation is the case 

 that c is to be regarded as infinitely great, a, b y I as finite. In 

 this case, of the terms whose sum constitutes the value of p, 

 all vanish in which n has a value different from 0, and we get 



9 abk 



abks/ir abksj^ v /J \2 V « 2 6 2 / 



where, in taking the sum, all the whole numbers from — oo to 

 + go are put for I and m. 

 If we make 



\=~ 



7T 



