the Electrical Conduction produced by it, 157 



of the negative ions reach the uranium and give up their 

 charge to it before recombination can take place. 



Fig. 14. 



If the radiation fell between two plates of exactly the same 

 metal, the inequality between the positive and negative 

 current values for low voltages would almost disappear, but 

 even in that case there would still be an apparent current 

 through the gas, due to the fact that the negative carriers 

 diffuse with greater rapidity than the positive. Effects of 

 this kind have been studied for Eontgen radiation by Zeleny *. 



For large E.M.F.'s no appreciable difference in the value 

 of the current could be detected whether the uranium was 

 positively or negatively charged, i. e. positive and negative 

 electrifications are discharged with equal facility. 



For the different gases the current tends more rapidly to a 

 saturation value in hydrogen than in air, and more rapidly in 

 air than in carbonic acid. In all these cases there is still a 

 slight increase of current with increase of E.M.F. long after 

 the " knee " of the saturation curve has been passed, and in 

 no case has complete saturation been observed at atmospheric 

 pressure, even for a potential gradient of 1300 volts per cm. 



The explanation of the general form of the curves showing 

 the relation between current and electromotive force for 

 ionized gases has been given in a previous paper f. In the 



* Phil. Mag., July 1898. 



f J. J. Thomson and E. Rutherford, Phil. Mag. November 1896. 



