458 Messrs. V. Cremieu and H. Pender 



on 



time touched a brush A connected to the earth ; they there- 

 fore became charged by influence. They then passed from 

 under the brush A and the fixed sectors S and came around 



under the astatic system. Beyond the system they met a 

 second brush B connected to the earth, thus becoming dis- 

 charged. By placing a galvanometer between A or B and 

 the earth, one can measure the charging current or the 

 current resultino- from the discharo-e. 



Certain phenomena, first observed by Cremieu, of solid 

 dielectrics, to which we shall return further on, led us to 

 employ in our joint experiments micanite sectors entirely 

 gilded, so as to avoid all action of the penetration of the 

 charge into the naked micanite. The astatic system was 

 suspended in a metallic tube connected to the earth. To 

 protect this tube from the electrostatic action of the moving 

 sectors, which were at a very high potential, Cremieu employed 

 a paraffined tube of mica fixed directly on the metallic tube. 

 To this disposition there are two objections. Since the 

 bottom of the tube is small relative to the area of the mo^^ing 

 sector, at the moment when the sector comes under the tube 

 there is a considerable increase of capacity of that portion 

 of the sector directly under the tube. Conseqtiently to this 

 point there will be a flow of charge by conduction-currents, 

 distributed in a manner impossible to calculate, which may 

 act upon the system. Secondly, in consequence of the 

 peculiar phenomena of the dielectric to which reference has 

 been made, the mica protector of the tube is submitted to a 

 penetration of charge from which may result considerable 

 perturbations. To avoid these 



