184 



Dr. C. Sheard on the Positive 



probably the correct one, although other experiments using 

 a " fresher" wire are necessary before definitely settling this 

 point. 



After the wire had been allowed to stand cold in C0 2 for 

 five days, a maximum current^ of 0*49 div. per sec. was ob- 

 tained at 654° C, similar to the maximum effect at the same 

 temperature in air or hydrogen given in Curves I. and III. 

 of fig. 1. 



YI. The Current-Time Relations. 



Fig. 4 shows the decay with time of the positive currents 

 at +200 volts : Curve 1 at 654° C, Curve 2 at 714° C, 

 Curve 3 at 738° C., and Curve 4 at 774° C. Fig. 5 shows 

 similar relations after the wire had been heated in the Bunsen 

 flame : Curve 1 at 628° C, Curve 2 at 690° C., Curve 3 at 

 738° C, and Curve 4 at 765° C. It will be seen that Curves 2 



Fig. 4. 



14 lb 18 20 

 Time - Minutes. 



and 3 of fig. 4 and Curves 2 and 3 of fig. 5 show that the 

 decay effect is a composite one, indicating the presence of 

 one substance which decays initially from a maximum value 



