Photoelectric Fatique of Metals. 



571 



4. Fatigue depends on the size of the containing vessel. 



The influence of the size of the containing vessel on the 

 rate at which fatigue takes place was verified during the 

 present investigation. Examples of this influence have 

 already been recorded in the earlier parts of the paper. If 

 Ave compare the results of Tables I. and II. with those of 

 Table III., we find that the fatigue is more rapid in the air 

 of the room than in the testing vessel. The same difference 

 is also shown in Table IV. Similar effects are mentioned in 

 § 8 with regard to silver and copper. 



Inasmuch as the rate of fatigue varied somewhat from day 

 to day, probably being dependent on the state of the atmo- 

 sphere at the time, it seemed desirable to have a direct 

 comparison between the fatigue in the room and that in the 

 testing vessel when the air was in the same condition. The 

 results of experiments made on the same day are recorded in 

 Table VII. 



Table VII. 



Zinc plate. Fatigue period, 16 minutes. 



In air of room. 



In testing yessel. 



Emery. 



Rouge. 



Emery. 



100 



100 



ICO 



P6 



89 



90 



79 



79 



82 



72 



73 



79 



67 



67 



77 



64 



64 



75 



59 



58 



72 



57 



55 



71 



53 



52 



69 



The fatigue is diminished by putting the plate in the 

 smaller receptacle. Incidentally we notice that the fatigue 

 proceeds at the same rate when the plate is rubbed with 

 emery-paper only as when this is followed by the application 

 of rouge paper. 



Conclusion, 



There has been much discussion as to the nature of the 

 change associated with photoelectric fatigue. The principal 



