238 Mr. E. C. Rimington on 



and we have an additional equation, 



— Xi; = v/C, 

 whence 



uX = cX 2 i? . 



Thus the subsequent investigation is the same as that of the 

 last section if we replace L by CX 2 , and the condition of 

 zero-deflection is 



aMb + d 2 =CX*m*. 



XXVIII. Note on Comparing Capacities. 

 By E. C. Remington*. 



LET two condensers, of capacities K Y and K 2 , be con- 

 nected to the arms A and D of a Wheatstone-bridge, 

 as shown in woodcut ; and 

 let »n t^t^ 7K.. \ . ^ — ^y ,7c. 



AC = BD, 



so that there is a balance 

 for permanent currents. 



Let %-\-y, x, z, and w be 

 the cyclic currents at some 

 moment after the battery- 

 circuit is broken, and when 

 the condensers are dis- 

 charging ; and let q 1 be 

 the charge on K x and g 2 

 that on K 2 at this moment. 

 Then we have 



(A + B + G)(a?+y)-G#-A* = 



Of, 



also 

 Therefore 



(C + D + G>-G(tf+y)-DM7 = 0; 



dqi 

 dt 



_dq^ 

 dt 



(A + B> + (A + B + G)y=A^, 



(C + D)*-Gy=D^. 



* Communicated by the Physical Society : read June 25, 1887. 



t The self-induction of the galvanometer need not be taken into 

 account, as the current in it commences and ends at zero. The arms 

 A, B, C, and D are supposed to possess no self-induction. 



