The Photo-. Electric Effect of some Compounds. 



\§1 



however, indicates the fact that salts have no real photo- 

 electric effect of their own, and that the effect of the light 

 is first, to decompose the salt, and second!}', to cause an 

 emission of electrons from the metallic element which is left. 



The Apparatus. 



The apparatus used is shown in fig. 1. A more detailed 

 description is given in my paper on the emission velocities of 



Fijr. 1. 



2 VOltS 



photo-electrons. The nickel disk N can be raised up or down 

 by means of the winch W. When in the position shown, 



