62 ELEMENTS OF STATIC ELECTRICITY. 



the leaves will remain divergent after its removal, but 

 show no increase of divergence by the contact; and the 

 ball, after removal, will be found entirely discharged. 

 This experiment proves : 



1. That the induction of the electrified ball has re- 

 pelled electricity from the inner to the outer surface of 

 the pail if the charge was positive, or attracted elec- 

 tricity from the outer to the inner surface if the charge 

 was negative ; in either case producing a divergence of 

 the leaves. 



2. It proves that induction increases as the ball de- 

 scends, shown by the increasing divergence of the leaves, 

 till all the lines of force, which can be included within 

 the pail, are cut by its surface, after which there is no 

 further increase of divergence. 



3. It proves that there is no permanent effect if 

 there is no contact ; since the leaves converge when the 

 ball is removed. 



4. It proves that the induced charge on the pail is 

 exactly equal to the charge on the ball, since no increase 

 of divergence occurs from contact, although the entire 

 charge has been communicated to the pail, as shown by 

 the ball having lost its charge. But this can be strictly 

 true only when all the lines of force are cut by the pail ; 

 but since some of the nearly vertical lines must escape, 

 no matter how deep the ball descends, there must be a 

 slight increase of divergence by contact, though it may 

 not be perceptible. 



If a charge be given to the pail and the ball be low- 

 ered into it by a wire held in the hand, the divergence 

 of the leaves, caused by the charge on the pail, will be 

 perceptibly reduced as the ball descends. 



This proves that the inner surface of a hollow con- 



