ELECTRIC GENERATORS. 109 



is revolved by a crank with an ebonite handle. The 

 relative sizes of the wheel and pulley are such as to 

 give the plate four to six revolutions for each revolu- 

 tion of the driving wheel, the plates of small ma- 

 chines requiring a more rapid revolution than those of 

 larger ones. In front of the plate A, J of an inch from 

 the glass, are the combs T^and H, attached to a brass 

 core at the center of the ebonite disc M ; and the 

 combs IT and L, insulated by their attachment to ebon- 



Fig. 36-The Holtz Electric Machine. 



ite rods projecting from the disc Jf, and connected by 

 brass rods with the Leyden jars C and D, and with the 

 sliding-rods P and R. These sliding-rods have ebonite 

 handles, and terminate in brass balls at their inner ex- 

 tremities. 



The plates are of sheet glass, about \ of an inch thick ; 

 of good insulating quality, and well coated with shellac. 

 The stationary plate B has two circular openings called 



