168 ELECTRICAL PROPERTIES OF SILK. 



the most remote, which always kept an electricity 

 opposite to that of the plate. 



The following experiments were performed by' 

 Mr Nicholson, on an improved method of excita-j 

 tion, as well as the action of points, and the direc- 

 tion of the fluid in positive and negative electricity^ 



1. A glass cylinder was mounted, and a cushion |. 

 applied with a silk flap, proceeding from the ed 

 of the cushion over its surface, and thence hall! 

 round the cylinder. The cylinder was then excited! 

 by applying an amalgamed leather in the usuall 

 manner. The electricity was received by a con- 1 

 ductor, and passed off in sparks to Lane's electro-l 

 meter. By the frequency of these sparks, or by the] 

 number of turns required to cause spontaneous ex-1 

 plosion of a jar, the strength of the excitation was. 

 ascertained. 



2. The cushion was withdrawn about one inoJM 

 from the cylinder, and the excitation performed ml 

 the silk only. A stream of fire was seen betweelfl 

 the cushion and the silk ; and much fewer sparH 

 passed between the balls of the electrometer. 



3. A roll of dry silk was interposed, to prevent 

 the stream from passing between the cushion and 

 the silk. Very few sparks then appeared at the 

 electrometer. 



4. A metallic rod, not insulated, was then inter- 

 posed instead of the roll of silk, so as not to touch 



