the Electrical Conduction produced by it. 



135 



With the notation previously used, the total ionization between 

 A and B (on the assumption that the radiating surface is 

 infinite in extent) is readily seen to be equal to 



-i- < g-Mo^l £-Mo^2 > 



This is a function of the pressure, and is a maximum when 



dje-rMj —d^e~ pK ^ = 0, 

 i. e. when 



The value of pX for air at 760 mm. is 1*6. 



Fig. 6. 



£00 



600 



600 



If ^2 = 3 cm., ^i = l, the leak is a maximum when the 

 pressure is about J of an atmosphere. On account of the 

 large distance of the plates from the uranium surface in 

 the experimental arrangements, no comparison between 

 experiment and theory could be made. 



In all the investigations on the relation between the pres- 

 sure and the rate of leak, large electromotive forces have 

 been used to ensure that the current through the gas is 

 proportional to the total ionization of the gas. With low 

 voltages the relation between current and pressure would be 



