produced in Gases by Bontgen Rays Sfc. 



421 



the external coating of the leyden-jar. The internal coating 

 was a disk of aluminium insulated on paraffin. The uranium, 

 which was a disk 55 centim. diameter, *5 centim. thick, was 

 placed inside a cardboard cylinder with one end open and the 

 other covered with aluminium, thin enough to be transparent 

 to the uranium influence, so as to touch the aluminium end 

 (see fig. 2). 



Ffr.S. 



Ut 



PARAFFIN LEYDEN 



ALUMINIUM TUBE 



This cardboard cylinder could be moved backwards and 

 forwards in. the aluminium cylinder, so that the distance 

 between the insulated disk in the latter and the aluminium 

 end of the former could be varied. The uranium thus acted 

 through the aluminium end of the cardboard box and made 

 the air between the end and the insulated aluminium disk 

 conductive. The leakage was in this way made slow enough 

 to be easily observed in the electrometer. The rate of leak 

 was not perceptibly increased when the piece of uranium was 

 heated nor when the sunlight fell on it. 



The aluminium end of the cardboard box and the outside 

 coating of the aluminium cylinder were connected to the 

 case of the electrometer. The insulated aluminium disk was 

 connected to the inside coating of the leyden B. These 

 inside coatings were charged to a known potential and then 

 left to themselves. The air-space between the insulated 

 aluminium disk and the aluminium end of the cardboard box 

 was 2 centim. The voltages used were therefore voltages per 

 two centim. of this air-space. With this arrangement the 

 leakage per minute — the necessary correction due to the 

 natural leakage with uranium removed having been made — 

 at various voltages was : — 



