CH. VI.] 



DISCHARGE BY LIGHT 



61 



negatively charged plate, under the influence of 

 light ; first without, and then with, a magnetic 

 field of measured strength applied across the region 

 between them. 



A little calculation of extreme beauty showed him 

 that the paths of the flying particles under magnetic 



Ga.uze 



Zinc 





FIG. 9. Diagram showing the theoretical paths of the electrons 

 emitted from clean negatively-charged zinc in ultra-violet light, under the 

 influence of a strong perpendicular magnetic field ; the zinc and gauze 

 being a magnified representation of the AB and CD in fig. 8. The rays 

 would naturally reach the gauze and convey a current to the electrometer, 

 but under the influence of the magnetic field their paths become cycloids 

 and they fail to reach the gauze unless it is brought nearer. The critical 

 distance between the zinc and the gauze when they are just able to 

 reach it is what is measured. 



influence would be cycloids, whose generating circles 

 contained the ratio m/e as well as the ratio E/H 2 ; 

 that is to say their trajectory, if it could be observed, 

 would involve the electrochemical equivalent required, 

 and likewise the ratio of the electric to the magnetic 



