INDUCTION. 45 



electricity is attracted from the leaves to the disc, and 

 they diverge, being negatively electrified, and mutually 

 repellent, as before, and attracted by the higher poten- 

 tial of surrounding bodies. 



Now, when the disc is touched with the finger, and 

 thus connected with the earth, if the charge is positive, 

 the potential of the electroscope is changed by the 

 escape of electricity to the earth under the influence of 

 the electrified body, and the leaves converge. But if 

 the charge is negative, the potential of the electroscope 

 is changed by the attraction of electricity from the earth, 

 and the leaves converge as before, equilibrium being re- 

 stored between the disc and leaves in each case. 



The leaves remain convei gent so long as the electrified 

 body is held near ; the electroscope being still under the 

 influence of the force by which the change of potential 

 was produced ; which is evidently just equal to the re- 

 pelled, energy in the first instance, and to the attracted 

 energy in the second. But when the electrified body is 

 removed, this equilibrium is disturbed, and the leaves 

 diverge under the influence of mutual repulsion and 

 outward attraction, as already explained. 



This experiment proves that a body connected with 

 the earth, and under the influence of induction, may 

 differ in potential from the earth, and is not necessarily 

 at zero potential from its earth connection. For it is 

 evident that such difference of potential existed during 

 the connection of the electroscope with the earth, else 

 it could not have become manifest when the connection 

 was severed and the inductive influence removed.. For 

 when the electrified body is removed before such con- 

 nection, the leaves converge, but when removed after it 

 has been made and severed, they remain divergent; 



