Smithsonian Report, 1910. — Deslandres, 



Plate 3. 



^ / 



l^:-;;#^ 



^ J 



'»^ 



Upper layer of calcium. 



21 SJO 



Upper layer of hydrogen mixed with a portion of the mean layer. 



Spectroheliograms of March 21, 1910. 

 (Negatives.) 



