Smithsonian Report, 1920. — Wychoff. 



Plate 6. 



Fig. 15.— The X-ray spectrum of tungsten using sodium chloride (cube face) as a grating. 



P* 



Fig. 16. — The powder spectogram from powdered silicon. 



Fig. 17.— The powder spectrogram from diamond. 



I I 



Fig. 18. — The powder spectrogram from nickel. 



Fig. 19.— The powder spectrogram from magnesium. 



