470 MEASUREMENT OF CAPACITY. DIELECTRICS. 



If the intensities are the same at the beginning and at the end 

 of each of the discharges that is to say, if the permanent regime 

 has time to re-establish itself, and that no magnet or external cur- 

 rent has been displaced or modified the quantity comprised within 

 brackets is null, and we have 



-2*0 = 0. 



Let / be the intensity of the current for the permanent regime, 

 and m = m r -t' 6 the excess of the discharge over the quantity of 

 electricity which would correspond to this regime. The preceding 

 equation may be written 



- S?] = , 



and, as the second term is null, we have simply 



= . 



Thus, in the conditions mentioned, we may say that the discharge 

 m adds itself to the permanent currents, and divides itself between 

 the different branches according to their respective resistances, and 

 independently of the electromotive forces which they contain. 



1059. This general theorem leads to several special methods. 



If the network consists of a single wire of resistance r, and if 

 the same current is established in the two experiments, either by the 

 discharges of the condenser or by an auxiliary resistance R I} we have 



this is the method of 1056. 



1060. If the points P and N are united by two resistances r and 

 r' (Fig. 223) the first of which contains an electromotive force E , 

 the resistance of the network is 



i rr 



2 i i r+r' 



