170 . Mr. G. W. Todd : Farther Experiments on the 



frequencies, while at high pressures it was impossible, with 

 the limited frequencies obtainable with the apparatus used, 

 to get any increase in the mobility. Without doubt, if the 



Frequency n. 



Mobility u. 





55 



3710 





92 



3750 





103 



3690 





122 



3670 





178 



3810 





210 



4010 





257 



4490 





286 



4520 





318 



5020 





frequency could have been increased sufficiently an increase 

 would also have been observed in these cases. From several 

 curves showing the relation between the mobility and 

 frequency for a number of pressures, fig. 3 was constructed. 



Fig. 3. 



300 



100 



It 



(00 







I 



50 



p (to in) 



(-00 



150 



At high pressures, whatever the rate of alternation used in 

 the experiments, the products of pressure and mobility lie 

 on the same curve. For frequencies of from 50 to 130 per 

 second no differences from curve I. could be detected. 



