182 



Dr. C. Sheard on the Positive 



(Curve V., fig. 1) corresponds to a small decrease in nega- 

 tive emission (Curve 3, fig. 2). The hydrogen presumably 

 accelerates the formation of positive ions, following out the 

 theory presented in the previous paragraphs, by inhibiting 

 the recombination of positive and negative ions produced by 

 heating. If this is so and if the gas has an affinity for 

 electrons, one might expect at high temperatures an escape of 

 hydrogen molecules carrying negative electrons ; these would 

 be held bound, in part at least, at the surface of the wire 

 under an opposing electric field. Recombination of positive 

 ions from the wire with the discharged negatively charged H 

 molecules would occur, and the positive thermionic currents 

 would decrease with increase of temperature above a certain 

 point. 



The experimental results given in fig. 3 were obtained after 



Fig. 3. 



7gO° 8IO°C 



Tem.fi.era+u.re- 



the treatment discussed with reference to Curve III., fig. 1. 

 The negative ionization-temperature relations before heating 

 in the Bunsen flame are given in Curve 1 of fig. 2, and similar 



