produced in Air hy Ultra-Violet Light. 



4-87 



In order to obviate time measurements and to be independent 

 of any variations in the intensity of the light or of the X-rays, 

 the quantit}' of electricity received by the " near " electrode N was 

 measured as well as that received by the " far " electrode F. The 

 total quantity received by N and F was taken as a standard and 

 the actual value received by F was divided by this. This was the 

 quantity plotted in the curves. 



The velocity of the air was indicated by the pressure drop 

 across a small plug of cotton-wool at E and was kept at approxi- 

 mately the same value throughout each series of experiments. 



Both electrodes were connected to Wilson tilted electroscopes 

 and to capacities of about 400 cms. The electroscopes were cali- 

 brated after each reading by means of a potentiometer. 



Table I. lonisation produced hy Ultra-Violet Light. 



n = quantity of electricity received by "near" electrode. 



f— "far" 



f 

 F= = quantity of electricity received by " far" electrode for a given number of 



n + J 



ions passing into the ionisation cylinder. 



Table II. lonisation produced by X-rays. 



Potential ou 

 cylinder 



8 volts 

 10 

 12 

 14 

 16 

 18 



Potential on 

 cylinder 



+ 10 volts 



+ 12 „ 



+ 14 „ 



+ 16 „ 



+ 18 „ 



+ 20 „ 



+ 26 „ 



