56 Mr. E. C. Kimington on a Method of 



self-induction in D 



La A + B 



~ G(A + B) *G+A + B 



C+D+ G+A+B 



-, since AC = BD. 



B(C + D) + G(B + C) J 



The quantity which passes through the galvanometer, due to 

 the discharge of the condenser, 



K r C + D 



" A + B+ G(0 + D) Xg + C + D 



G+C + D 



Kyr 2 C 



B(C + D) + G(B + C)' 



since AC = BD. 



Now these quantities obviously pass through the galvano- 

 meter in opposite directions ; and if there is no throw, they 

 must be equal. Therefore 



L^B Kyr 2 C 



B(C-t-D) + G(B + C)~ B(C + D) + G(B + C)' 



X 



B 



Now y T> T Tr 2 D 



If r=B, we have Maxwell's method, and 



L = KBD. 



Of course it is not necessary to use two sliders ; one 

 armature of the condenser can be connected either to the 

 junction of A and B or to the junction of B and C, and the 

 othe** to the slider ; but by having B composed of two slide- 

 resistances, the smaller one being equal to the resistance of 

 one of the coils of the larger, and employing a slider on each, 

 a much greater range of adjustment can be obtained. 



Suppose r to be slightly out of adjustment by an amount 8. 

 Then the quantity which passes through the galvanometer, or 



_ K(r + 8) 2 Cy-BL.g 



?-"B(C + D) + G(B + <j/ 



XT D 



Now ? = *q; _ K(r + S) 2 D-BL 



