60 



FLUORESCENCE OF THE TJRANYL SALTS. 



From this investigation by Misses Wick and McDowell, two definite 

 conclusions may be drawn: 



(1) The spectrum of the long-time phosphorescence produced by 

 cathode-ray excitation at liquid-air temperatures is identical with the 

 fluorescence spectrum. 



20 



10 



SO 



too 



SECONDS 



FIG. 51. 



(2) The decay curve of the cathode phosphorescence differs in the 

 most striking manner from that of the brief photo-phosphorescence. 

 It corresponds in type with that usually found in cases of phosphores- 

 cence of long duration. 



