Resonance Potentials for Electrons in Metallic Vapours. 39 



the first point of resonance was very difficult to obtain. 

 Only one curve, 9, shows this point clearly; and even in 

 this case the value of the potential could not be observed 

 with great enough precision to justify its use in determining 



Fig. 3. 



I Z34567S 



Acceleratinq Potential Volts 



Variation with accelerating potential of current to outside cylinder 

 and of total current from hot wire. Thallium. 



the final value of the resonance potential. The fact that this 

 point does not show up as distinctly as the other resonance 

 points is due to the temperature distribution of initial velo- 

 cities of the electrons, and to the thermionic emission of all 



