Publications of the Astrophysical Observatory 



This series, Smithsonian Contributions to Astrophysics, was inaugurated 

 in 1956 to provide a proper communication for the results of research con- 

 ducted at the Astrophysical Observatory of the Smithsonian Institution. 

 Its purpose is the "increase and diffusion of knowledge" in the field of astro- 

 physics, with particular emphasis on problems of the sun, the earth, and the 

 solar system. Its pages are open to a limited number of papers by other 

 investigators with whom we have common interests. 



Another series is Annals of the Astrophysical Observatory. It was started 

 in 1900 by the Observatory's first director, Samuel P. Langley, and has been 

 published about every 10 years since that date. These quarto volumes, some 

 of which are still available, record the history of the Observatory's researches 

 and activities. 



Many technical papers and volumes emanating from the Astrophysical 

 Observatory have appeared in the Smithsonian Miscellaneous Collections. 

 Among these are Smithsonian Physical Tables, Smithsonian Meteorological 

 Tables, and World Weather Records. 



Additional information concerning these publications may be secured from 

 the Editorial and Publications Division, Smithsonian Institution, Washing- 

 ton, D.C. 



Fred L. Whipple, Director, 



Astrophysical Observatory, 



Smithsonian Institution. 



Cambridge, Mass. 



For sale by the Superintendent of Documents, U.S. Government Printing Office 

 Washington, D.C, 20402 - Price 40 cents 



