14 



L. G. Rauh 



nitrogen ions would carry a relatively higher proportion of the 

 current, and as the current is increased the more mobile helium 

 ions carry a larger percentage of the current, thus giving higher 

 average mobility. Spectroscopic examination of the glow tends 

 to support this explanation, since the helium lines become rela- 

 tively much more intense as the current density is increased. 



The law that the product of the mobility times the pressure is 

 constant is found to hold at higher gas pressures. In order to 

 compare mobilities obtained at different pressures, the value, U^, 

 of the mobility at i mm. pressure was computed for each case on 

 the basis of the above law. The values of U^ in the two tables 



37S 



t6/A5 



/JS 



J L 



■/B -2^ . 



.yo 



.'9'S'C'r, 



Fig. 6 



