424 Drs. Beattie and Do Smolan on the Conductance 



With ulira- violet light we have as yet only observed the 

 rate of leak from a charged body for voltages up to two 

 or three volts. The method we employed is one originally 

 used by Righi. 



A cage of brass wire gauze was made and connected to the 

 case of the electrometer. Inside it the insulated metal was 

 placed on a block of paraffin, and connected to the insulated 

 terminal of the electrometer by a wire protected against 

 inductive effects. The light from an arc lamp was then 

 let shine through the gauze so as to fall on the insulated 

 metal perpendicular to its surface (see fig. 5). 



Fig. 5. 



ELECTROMETER 



With this arrangement we found when the insulated metal 

 was zinc, aluminium, or copper, and when a positive or 

 negative charge was given to any one of these metals when 

 insulated, that positive and negative charges leaked away at 

 the same rate when the light from the arc lamp fell on the 

 charged metal, the positive or negative charges being- 

 reckoned from the steady electrometer reading which is 

 obtained when the two quadrants of the electrometer are 

 insulated and the ultra-violet light shining. Our results on 

 leakage through air from a body illuminated by ultra-violet 

 light agree with those obtained by Branly. 



§ 3. Effect of Kontgen Rays on the Conductance of Paraffin 

 and of Glass. 



In our first experiments with paraffin we used a brass ball 

 of about an inch in diameter, connected to the insulated 

 terminal of the electrometer by a thin wire soldered to the 

 ball. The ball and the wire were both coated to the depth of 

 about an eighth of an inch with paraffin. The ball was then 

 laid on a block of paraffin in a lead box with an aluminium 

 window, both of which were in metallic connexion with 

 the case of the electrometer. 



The paraffined ball was then charged positively, and the rays 

 caused to play on it. After two minutes the electrometer 



