Smithsonian Report, 1940.— McMath 



PLATE 1 



Photographs of the Solar Disk. 

 A, B, and C, disk of August 18, 1939. A, direct; B, Ha spectroheliogram; C, Ca+ spectroheliogram. 

 D and E, sunspot group of September 1, 1939. D, direct; E, Ha spectroheliogram. 

 F and G, Ha spectroheliograms of a sunspot group approaching the limb of the sun. F, September 14, 1939 



G, September 16, 1939. 



