206 ELEMENTS OF ELECTRICITY AND MAGNETISM. 



arrows until the carriers come under brushes 5 and 6 where they 

 part with a portion of their charges, thus replenishing inducing 

 charges on AA and BB. The carriers are then moved into 

 the space between AA and A' A' on the one hand and into the 

 space between BB and B' B' on the other hand where they 

 come into contact with the brushes I and 3, thus giving up the 

 remainder of their charges to the metal terminals TT of the 

 machine. When a spark is formed between the metal terminals 

 TT, the bodies A' A' and B' B' become completely discharged, 

 but the induced charges on AA and BB remain and the 

 machine continues to operate. 



The Toepler-Holtz machine is self-exciting, that is to say, the 

 extremely minute electromotive forces due to the contact of the 

 metal brushes with the metal buttons on the carriers are sufficient 

 to start the operation of charging by influence, and the action of 



Fig. 132. 



the machine is then rapidly intensified by the doubling action 

 which takes place. 



115. The Wimshurst machine. A general view of the Wims- 

 hurst machine is shown in Fig. 132. It consists of two oppo- 

 sitely rotating glass disks on each of which a number of metal 



