Resonance Potentials for Electrons in Metallic Vapours, 35 



upon the current, rather than the position o£ maximum effect. 

 These are determined by carefully plotting and extrapolating 

 the lower portion o£ each curve. The point selected as 



Fig. 1. 



-s%/ 



2 4 6 8 



Acce/erstino Potential Volts 



10 



Variation with accelerating potential of current to outside cylinder 

 and of total current from hot wire. Magnesium. * 



<z, b, c, &c, is the voltage at which the observed curve 

 deviates from the extrapolated curve by a small pre-assioned 

 amount. The difference in the voltages corresponding to 



D2 * 



