THE ELECTROPHOBUS. 



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5/D 



effect is produced. Now since the previous experi- 

 ment proves that bag and sealing-wax are really 

 charged by the rubbing, and that their charges are of 

 an opposite kind, the last experiment proves that both 

 charges must be equal, for they neutralise one another 

 exactly. As soon as the bag is pulled off, the two 

 equal opposite charges manifest again the effects 

 already described, and it is clear that in order to pro- 

 duce these effects local separation of the two electricities 

 must take place first. 

 / The Electrophorus is an instrument for generating 



FIG. 310 (A, C, an. proj ; A, % real size; B, C, real size\ 



in a simple manner by induction a somewhat greater 

 supply of electricity. It consists of a conducting 

 support, /in fig. 310 A, called the form, upon which is 

 placed a circular disc of some substance which is easily 

 electrified by friction, usually a cake of resin or a disc 

 of ebonite, k. Besides this there is a metal disc, or 

 4 cover,' J, to which are attached three insulating 

 threads of silk, tied together at one end, by means of 



