Smithsonian Report. 1939.— Harrison 



PLATE 3 



1. "Rainbow Spectrum" of Crystals Containing Hafnium salts. Taken 

 With a Microscope and Spectrograph in Combination. 



Each "bow" is a spectrum line of a siven color, and the same microscoiiic reyion is photographed in each 

 color. The lower bow is an ultraviolet line, the upper bows are visible lines. 



2. Same Type of Spec tromicrogram as in Fig. 1 (Abovei. but With Hafnium- 

 Containing Crystals in the Field. 



Note the darkening produced by absorption of ultraviolet light by the hafnium crystals in the lower bows 

 and the relative transparency of the hafnium in the upper bows. 



