11] IONIZATION THEORY OF GASES 33 
Taking into consideration the early part of the curves, the 
current does not reach a practical maximum as soon as would be 
expected on the simple ionization theory. It seems probable that 


Saturation Curves 
for 
Uranium rays 
Current 








0 20 40 60 80 100 
Volts 
Fig. 4. 
the slow increase with the large voltages is due either to an action 
of the electric field on the rate of production of ions, or to the 
difficulty of removing the ions produced near the surface of the 
uranium before recombination. It is possible that the presence 
of a strong electric field may assist in the separation of ions which 
otherwise would not initially escape from the sphere of one 
another's attraction. From the data obtained by Townsend for 
the conditions of production of fresh ions at low pressures by the 
movement of ions through the gas, it seems that the increase of 
current cannot be ascribed to an action of the moving ions in the 
further ionization of the gas. 
28. The equation expressing the relation between the current 
and the voltage is very complicated even in the case of a uniform 
rate of production of ions between the plates. An approximate 
R. R.-A. 3 
