and the Resonance Radiation of Electrons, 



517 



By means of two right-angled prisms it was possible to 

 substitute a powerful beam of sunlight for the mono- 

 chromatic beam, by which the spectrum of the fluorescence 

 provoked by white light could be easily photographed or 

 observed. 



u 



* -T=!(=r 



\i ' 





\ \\ i 



^Z__J^r 







i 



i 1 



— __ 



, 1 



With white light illumination the fluorescence spectrum 

 is made up of a large number of hazy lines, which in the 

 yellow and yellow-green region are arranged in groups or 



