Foote & Meggers, 



Phil. Mag. Ser. 6, Vol. 40, PL I, 



too-) 

 <OlO. 



£ 

 ? 







to 1 * o 

 to vo cn 



10 io io 



-6213 

 '6355 

 -6723 

 -6973 



4 *o-^r> 



<0 0*IO<J> 



Applied 



■accelerating 



potential 



in volts 



Low voltage arc spectra 

 of caesium vapor 



True 



accelerating 



potential 



in volts 



