Critical Velocities for Electrons in Helium. 



597 



increased production of radiation at the second and third 

 multiples of the resonance potential difference. 





10 20 30 40 



Electron ve/oc/'ty (volts) 



Fio-. 3. 



50 



60 



70 



80 



i 





■ii 



























































































m 









\>fc 



©P^ 



























^©n 



3<5v 

























^1 



^ 











1 















\ 











& 



1 

















k 





























\ 



























\ 





50 



60 



70 



10 ZO 30 40 



E/ectron velocity (vofts) 



Fig. 3 also represents a series of observations of the 



variation with the velocity of the electrons, of the current 



