480 MEASUREMENT OF CAPACITY. DIELECTRICS. 



we may write 



and if, as is easily done, we choose the experimental conditions 

 so that the second term of the bracket may be neglected in com- 

 parison with unity, it reduces to 



Schiller made three consecutive experiments : with the wire 

 of the induced coil simply open; with this wire connected with a 

 plate condenser and comprising an insulating plate; and, finally, 

 with this same condenser when the insulating plate is removed and 

 replaced by a plate of air. If T , T x , and T 2 are the times of 

 oscillations in the three cases y, y + />tC, y + C the corresponding 

 capacities, we deduce 





The mean time of charge was 0-00005 of a second. -^ 



1070. ACTION ON A DIELECTRIC SPHERE. The specific in- 



ductive power may also be deduced from the action which a 



constant electrical field y produces on bodies of small dimensions. 



For a homogeneous field of volume #, the component of this action 



in any direction (179) is expressed by 



uK^ 2 _u 3 p-i 3(ft 2 



~ 



The action X which would be exerted on a conducting sphere 

 of the same volume is 



u 3 D 



Ail ~~ -- "> > 



2 47T tbC 



from this follows 



