Smithsonian Report. 1940. — McMath 



Plate 4 



Formation of Prominence Loop, September 7. 1939, Ha Spectroheliograms, 

 A, lGi'20.1fi"'; B, lCh23.28'»; C IGhaO.Oe""; D, 16h32.87'"; E, 16i'38.43ffl; F, 17145.52", G. C. T. 



