﻿180 Mr. J. (-. Pomeroy on the Charges on Thermions 



in fig. 3. The charge is, of course, inversely proportional 

 to the potential difference necessary to give the same value 



Of Qr/Qc 



Fhr 3. 



Thus it would seem that at a temperature only sufficiently 

 high to give positive ionization, some of the ions from a fresh 

 strip, or from one which had been resting in air, carry charges 

 which are double the atomic charge ; but when the strip is 

 heated for a time a gradual change takes place, and as the 

 large initial positive leak dies away a smaller and smaller 

 proportion carry double charges, until a steady state is 

 reached where the average charge is nearly equal to the 

 atomic charge. 



However, as noted above, no such change takes place with 

 the negative ions, some of which at all times carry double 

 charges. Then, too, when the positive ionization from a strip, 

 heated to a sufficiently high temperature to give negative ions, 

 was tested it was found that the average charge was about the 

 same as for the negative ions. This result suggested that 

 probably the negative ions also would carry single charges 

 only, if obtained from a strip at a sufficiently low temperature. 

 The apparatus as arranged did not admit of very low pressures 

 being obtained, so hydrogen at atmospheric pressure was used 

 and the strip heated in this. 



As expected, the negative as well as positive ions carried 

 single charges only when obtained from a strip at the lower 

 temperature, and when this temperature w r as raised, both 

 positive and negative ions carried some double charges. The 

 proportion of these double charges to the whole number of 

 ions rose gradually with the temperature of the strip just as 

 with positive ions in air. 



No attempt was made to measure the temperature of the 

 strip, but keeping the same strip the heating current was 

 varied from the smallest which would give positive ionization 



