ELECTRICAL CONDENSERS. 



G17 



and 



so on. 



The instantaneous discharge of the apparatus is only 

 possible if both discs are connected by means of a good 

 conductor, as for example when both discs are touched 

 simultaneously by different fingers of the same hand, or 

 by placing one hand upon* the uppetf disc and the other 

 upon the lower. In that case the discharge is quite sudden 

 and instantaneous. On the contrary, if the connection 

 between the two discs is made wholly or in part by a less 

 good conductor, the discharge takes place more slowly 

 and is less perceptible to the touch. Such a slow dis- 

 charge may be brought about by connecting the lower 

 disc by a wire with the table and bringing the finger 

 near the upper disc without touching the lower. The 

 discharge is retarded in this case, because the two elec- 

 tricities in order to unite have not only to pass through 

 the wire and the human body, both good conductors, 

 but also through the table and the floor, which are much 

 worse conductors. 



Apparatus like the one described, which serve for 

 condensing a large quantity of electricity on a compara- 

 tively small surface, and which consist essentially of two 



