Magnetic State of Iron and its Photo- Electric Properties. 351 



given is as before the mean of a separate series of 

 experiments. 



Table IV. 



Eate of Rise of Voltage per sec. 



Experiment. 



Field off. 



Field on. 



Arc current. 



1 



•104 



•105 ♦ 



25 



2 



•105 



•104 



25 



3 



•013 



•013 



1-8 



4 



•025 



•025 



1-5 



Summary of Paper. 

 It is shown that if we assume : — 



(a) That the same electrons in a ferro-magnetic atom 

 are responsible for its magnetic and photo-electric 

 properties ; 



and 



(b) That Lindemann's Resonance Theory of the emission 



of photo-electrons is correct ; 



then we might expect both a change in the total number of 

 electrons emitted by an illuminated ferro-magnetic surface 

 when it is magnetized, and also a possible change in the 

 original direction of emission. The evidence produced in this 

 paper shows that there is apparently no large change in the 

 total number of electrons emitted, though a change of 1 to 

 2 per cent, could not be detected. So far no very satisfactory 

 experiments have been conducted on the second point. 



In conclusion, I wish to express my thanks to Dr. Joly 

 for his kind interest and advice during the course of the 

 experiments. 



Iveagh Geological Laboratory, 

 Jan. 1921. 



