Wood.— Fluorescence of Sodium. 



Plate 2. 



Ill 



z 



blue 



green 



yellow 



n ^TTl] 



jiiiiliiltlij|«tokili 



iiiiiililidi 



n^fllfl 



fm 



Prog. Amer. Acad. Arts and Sciences. Vol. XLII. 



HELIOTYPE CO., BOSTON. 



