ELECTRIC GENERATORS. 



97 



using the glass globe, and a band wheel and belt to 

 increase their speed ; and collecting the electricity on 

 an iron tube, suspended by silk cords, from which hung 

 a chain in contact with the globe. 



Furt' er improvement was made by the use of a 

 leather rubber stuffed with hair : and subsequently the 

 globe was replaced by a glass cylinder, on one side of 



Fig. 29 Plate Electrical Machine. 



which the rubber was mounted on a glass pillar ; and, 

 on the other side, similarly mounted, was a brass cylin- 

 der, called the prime conductor, from which a row of 

 points projected toward the glass. An oil silk flap 

 enveloped the upper part of the glass cylinder ; and a 

 chain was used to connect either the rubber or the 

 prime conductor with the earth, as desired. 



The plate machine, invented about 1787, was con- 



