524 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



to the intensity of the current belonging to the point, its value would de- 

 crease when the current increased, in the manner shown in the subjoined 



table. 



TABLE IX. 



Figure 9. 



If, however, we write 



d(Li) 

 dt 



= E 



(40) 



and plot from the actual building-up curve given in Tigure 9, E — ri as a 

 function of t, we may get the area under this curve by means of a plani- 

 meter for a series of values of t, and determine L from the ecmation 



Li — f(E-ri)dt. 



(41) 



