476 Mr Baker, Influence of Ultra Violet Radiation, etc. 



(b) Ultra violet light falling on the kathode, 



250 cells start the discharge ; 

 249 cells do not start discharge. 



Very little importance is attached to the difference in the 

 potentials required to start the discharge in the two directions 

 in the dark, as the copper rod was in a narrow tube, while the 

 zinc had plenty of space about it. 



To Professor J. J. Thomson are due my best thanks for 

 suggesting the investigation and for his e^er ready advice and 

 encouragement. 



