ELECTRIC GENERATORS. 



103 



with the earth. Between the central and outer bells 

 are two small brass balls, suspended by silk cords. 



When the machine is put in operation, the outer bells 

 receive a charge from the prime conductor; this acts 

 inductively on the insulated balls, which are at zero, 

 attracts, and, after contact, repels them. Being now 

 charged the same as the outer bells, they act inductively 

 on the central bell, repelling or attracting electricity 

 through its chain, according as their charge is positive 

 or negative ; and pro- 

 ducing on it a charge 

 of the opposite kind, 

 they are attracted to it 

 and discharged. Be- 

 ing now at zero, they 

 are attracted to the 

 outer bells, as before ; 

 and in this way the 

 three bells are made 

 to ring. 



IMAGE PLATES. 

 These are used to 



show the effect of ill- Fi S- 32-Image Plates. 



duction between two conducting surfaces, as repre- 

 sented by Fig. 32. 



From the projecting rod of the prime conductor, a 

 brass plate, having a resistance rim, is suspended by a 

 wire or chain: and under it. on an insulating stand, is 

 placed another similar plate, made a little larger, and 

 joined to the insulating support by a sliding rod, by 

 which the distance between the plates may be adjusted, 

 a chain connecting it with the earth. 



When the machine is put in operation, the upper 



