Resonance Potentials for Electrons in Lead and Calcium . 75 



20, and 2b" are total current and curves 1, 3, 10, 19, and 23 

 partial current reaching the outer electrode. In all 19 partial 

 current curves and 12 total current curves were obtained of 

 which the curves illustrated are typical. The total current 



Fiff. 1. 



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Accelerating - Potentia/ t/o/ts. 



Electron Currents in lead vapour. Curves 4, 14, 20, and 26 " total 

 current " ; curves 1, 3, 10, 19, and 23 " partial current." 



showed ionization when the temperature reached 900° C, 

 but most of the data were obtained in the range 950° C. to 

 1050° C. Above the ionization point a blue arc was visible, 

 due probably to the line A. = 4058 A. 



