ELEMENTARY LESSONS ON [CHAP. I. 



a charge into the interior and repels a + charge to the 

 exterior. The gold leaves diverge more and more until 

 the ball is right within the hollow conductor, after which 

 no greater divergence is obtained. On letting the ball 

 touch the inside the gold leaves still remain diverging 

 as before, and if now the ball is pulled out it is found 

 to have lost all its electricity. The fact that the gold 



leaves diverge no wider 

 after the ball touched 

 than they did just 

 before, proves that 

 when the charged ball 

 is right inside the 

 hollow conductor the 

 induced charges are 

 each of them precisely 

 equal in amount to 

 its own charge, and the 

 interior negative charge 

 exactly neutralises the 

 charge on the ball at 



the moment when they 

 touch, leaving the equal 

 exterior charge un- 

 changed. An electric 



cage, such as this ice-pail, when connected with an 

 electroscope or electrometer, affords an excellent means 

 of examining the charge on a body small enough to be 

 hung inside it. For without using up any of the charge 

 of the body (which we are obliged to do when applying 

 the method of the proof-plane) we can examine the 

 induced charge repelled to the outside of the cage, 

 which is equal in amount and of the same sign. 



35. Distribution of Charge. A charge of elec- 

 tricity is not usually distributed uniformly over the 

 surfaces of bodies. Experiment shows that there is 

 more electricity on the edges and corners of bodies than 



