238 



PROCEEDINGS OP THE AMERICAN ACADEMY 



sary, on account of the self-induction of the measuring circuit, always 

 to read either on opening or on closing the key. In our experiments 

 the latter alternative was chosen. 



The results were plotted as previously by using the relative strength 

 of the field as expressed by tangents of the magnetometer deflections 

 as ordinates, and the induced currents in terms of an arbitrary unit 

 as abscissas. The deflection of the ballistic galvanometer used was 



Sp iOO /W 03 JiO 



Fig. 2. 



proportional to the strength of the transient current passing through 

 its coils. 



A series of observations was first made with the diaphragm removed, 

 in order to study the deportment of the core alone under varying de- 

 grees of magnetization. The results are given in Table VII., and are 

 shown graphically in Curve 1, Figure 2. It appears from these, that 

 with increasing magnetization of the core the induced current remains 

 nearly constant for a time, and then diminishes rapidly and at an in- 

 creasing rate, which afterwards becomes nearly constant, a result 

 which would be anticipated from the corresponding diminution in 



