of the Negative Thermionic Current in a Vacuum. 1Z1 



the current obtained from the secondary of a small trans- 

 former connected to an alternating dynamo, and the tem- 

 perature was varied as desired by altering the relative 

 positions of the primary and secondary, the latter being 

 supported on a platform capable of slow motion to and fro 

 along the axis of the primary. 



Fiffs. 1 & 2. 



To E lect ro m e ter 



B FIC. i. 



flC. 1 



The following table contains some representative obser- 

 vations made on the four metals mentioned. The currents 



