234 VARIABLE STATE. 



Suppose that at the moment / x we open the circuit, and leave the 

 apparatus to itself during a time / 2 , equation (13) reduces to 



denoting by E : the difference of potential at the time / : between 

 the armatures, by E 2 that which exists at the moment / 1 + / 2 , and 

 putting T 2 = CR, we have 



Suppose, lastly, that we discharge the condenser by connecting 

 the two coatings by a conductor of small resistance />, we shall have 

 the equation 



E E_ E 



+ ~ ^~* 



and, at the end of a time / 3 that is to say, at the period ^ + / 2 + / 3 

 E = E-| with T 



The total loss of the condenser during the time / 3 , is C (E 2 - E 3 ) ; 



the portion which traverses the outer circuit and constitutes the 



p 



discharge Q, is equal to C(E 2 -E 3 )- - , which gives finally 



JK. + p 



CR 2 



To have a complete discharge, we must make / 3 = oo ; we see 

 that we attain this complete discharge in a continuous manner, and 

 without any of the alternatives to which condensers give rise. 



Maxwell has shown that a system formed of parallel dielectric 

 layers, and even of different dielectrical elements mixed in any way 

 whatever, may give rise to residual charges, although each of the 

 constituent dielectrics is destitute of this property. But the want 



