Wellisch — Motion of Ions and Electrons through Gases. 21 



of the vapor the insulation was extremely defective and the 

 currents could not be determined by observation of the rate of 

 deflection of the electrometer needle. However it was observed 

 that the spot of li^ht assumed for each value of the potential a 

 definite position on the scale ; in this position the ionization 

 current is balanced by the current due to the leak through the 

 condensed vapor and is thus proportional to the steady reading 

 of the electrometer. The conductivity of the condensed vapor 

 remained constant over a sufficient interval to enable the critical 

 potential to be determined in this manner. Typical curves 

 obtained for saturated H^ are given in fig. 7.* The results of 

 the mobility determinations for saturated H, and CO^ together 

 with the calculated values for the dry gases at the same pres- 

 sure are given below : 



II, dry 



saturated 



CO, dry 



saturated 



p 



Kx 



K2 



mm. 







809 



4-80 



9^09 



809 



5-03 



6-105 



769 



•72 



1-06 



769 



•77 



•88 



In addition, other experiments were performed in which 

 small quantities of water vapor and ether vapor were mixed 

 with hydrogen ; in these experiments the mobilities were 

 determined in the ordinary manner. The following results 

 were obtained : 









P 



K, 



K2 









mm. 







H. 



dry 





r>l7 



7-51 



14-21 



H, 



with water 



vapor 



517 



7-43 



10-27 



H, 



with ether 



vapor 



766 



4^13 



7-25 



The presence of water vapor appears thus to be with'out eEiect 

 on the mobility of the positive ion but occasions a marked 

 diminution in that of the negative ion. This is in accordance 

 with the results obtained by previous investigators. 



* The current scale for these curves is different from that for the other 

 curves in fig. 7. 



