94 



ELEMENTS OF STATIC ELECTRICITY. 



plate and cover, by touching the strip and knob with 

 the finger and thumb, or a small discharger ; the elec- 

 tricity accumulated on the lower plate will pass to the 

 cover, producing a shock if passed through the hand. 



The cover thus becomes positive ; but its charge is 

 neutralized, or bound, by the negative of the dielectric. 

 Let it be lifted off by the insulating handle ; its charge 

 being no 'longer 'bound, a discharge, producing a spark, 



an inch or more in 

 length, takes place, 

 when the knuckle 

 or any conductor 

 is presented to the 

 knob, as shown in 

 Fig. 28. 



The removal of 

 the cover with its 

 positive charge, 

 having left the up- 

 per surface of the 

 dielectric negative, 

 a positive charge 

 is again attracted 

 to the under sur- 

 face and plate, as before ; and the cover, having been 

 discharged and replaced, the process may be repeated 

 with the same results an indefinite number of times, 

 and Leyden jars charged, or other electric work 

 performed. 



Suppose the original charge to be positive, the same 

 results occur in reverse order. Electricity having been 

 imparted by the fur to the upper surface of the dielec- 

 tric, the same amount is repelled from the under 



Fig. 28 Discharge of Electrophorus. 



