326 HENRY A. KOWLAND 



The current in the R" circuit is then 



C ci (bt + < J^/ 

 ^ r - T>H 



+ ibL" 



The current in the E circuit is 



= (7 e t. 



Substituting the value of C" e fbt in equation (1) and simplifying, it 

 becomes 



"r ibL"r 



FIG. 6. 



Therefore the deflection is proportional to 

 cos ($, 0,) = (7|~ 



and the condition for zero deflection is 



- VLMR'r + VL"Mr(R+r) = 0, 

 L _R+r 



The condition therefore of zero deflection is independent of M . But 

 M is one of the factors of the electromotive force in the R" circuit, and 

 on it therefore depends the sensitiveness, as it determines the current 

 through the R" circuit. In the first figures of this method the fixed 

 coils are in the R" circuit, and the hanging coil in the R circuit, but 

 this is not necessary, as the fixed and hanging coils can be reversed. 

 The choice of which of the above arrangements should be used depends 



