126 



ELEMENTS OF STATIC ELECTRICITY. 



C ; the tips of the arms being fitted to the holes in the 

 knobs of the jars. 



A bell is suspended from each arm by a brass rod ; 

 and a brass ball suspended by a silk cord from the 

 ebonite connector hangs between them. 



As each bell is at the same potential as the jar with 

 which it is connected, the ball is alternately attracted 

 and repelled, causing the bells to ring. 



Instruments of this kind have no practical use, except 

 to illustrate the principles of the science. 



c APPARENT TIME OF 



THE ELECTRIC DIS- 

 CHARGE AN OPTICAL 

 ILLUSION. The car- 

 riers on the revolving 

 B plate of a Topler afford 

 special facilities for 

 this experiment. They 

 are usually six discs, 

 arranged in a circle, 

 and present the ap- 

 pearance of a con tin- 

 Fig. 41-Chime for Topler Machine. ^^ ^^ ^ ^^ 



the machine is operated in the light ; but when oper- 

 ated in the dark, they are seen only when the spark 

 renders them visible ; and, instead of the bright ring, 

 each appears by itself, apparently motionless, and as 

 perfect in form as if really so, just as if the movement 

 of the plate were momentarily arrested during the 

 passage of the spark. 



This apparent time of the spark may be estimated 

 at i second ; but if the carriers were really visible 

 during that time, the ring-like appearance would be 



