30 Prof. A. Battelli and Mr. L. Maori 



on 



resistance equal to R, for currents of high frequency will be 

 given by 



p being — 2irn and A being a constant. This constant, as 

 results immediately from formula (20) of the quoted paper, by 

 putting p = 0, is connected to the self-induction for continuous 

 currents by the relation 



L =Z(A +i ). 



Hence the preceding formula may be given the form 



^-lOVS w 



For the various circuits above mentioned the value for L 

 is given for a square * of the perimeter I by 



L =2l(log e l - -1*9103 ), 



for a circle of the radius a by 



L = 47ra(log e ~- —1*75 J, 



r being the radius of the wire f . 



Wien J controlled the values for L , calculated by these 

 formulae and agreeing with each other to 0*1 per cent., 

 by those obtained from accurate measurements ; they thus 

 deserve full credit. By substituting them in the formula (1) 

 we may calculate the self-induction the above circuits exhibit 

 for each period of the discharges we have photographed the 

 spark of. 



The following values were thus obtained : — 



For the square of copper wire : 



T= 0-00000425, 0*00000303, 



L = 27390 cms., 27329 cms. 



For the circle No. 1 : 



T =0-00000235, 0*00000167, 0*00000120, 

 L = 7829cms., 7824 cms., 7810 cms. 



* This formula may be deduced by simple algebraical operations from 

 the one given in Mascart, Electr. et Magn. vol. i. p. 630, of the second 

 edition. 



t Mascart, /. c. p. 633. 



\ Wied. Ann. liii. p. 928 (1894). 



