22 



STUDIES IN LUMINESCENCE. 



.4/1 



.5U 



Fig. 19. White fluorite. 



Curve A. Fluorescence spectrum when excited by the carbon arc. 

 Curve B. Fluorescence spectrum when excited by Hg arc. 

 Curve T. Transmission spectrum of a layer 0.8 cm. thick. 



100 



eo 



to 



40 



?0 



.<IJ 



.5 ft 



Fig. 20. Greeu fluorite. 



Curve A. Fluorescence spectrum when excited by diffuse daylight. 



Curve B. The same repeated on another day. 



Curve T. Transmission spectrum of a layer 1.72 cm. thick. 



