APPENDIX 7. 



REPOET ON THE ASTROPHYSICAL OBSERVATORY. 



Sir : The Astrophysical Observatory was conducted under the f ol- 

 lowing passage of the sundry civil act, approved March 4, 1921 : 



Astrophysical Observatory : For maintenance of tlie Astropliysical Observa- 

 tory, under the direction of the Smithsonian Institution, including assistants, 

 purchase of necessary books and periodicals, apparatus, making necessary 

 observations in high altitudes, repairs and alterations of buildings, and mis- 

 cellaneous expenses, $15,500. 



The observatory occupies a number of frame structures within an: 

 inclosure of about 16,000 square feet south of the Smithsonian ad- 

 ministration building at Washington, and also a cement observing 

 station and frame cottage for observers on a plot of 10,000 square 

 feet leased from the Carnegie Solar Observatory on Mount Wilson,. 

 Calif. 



A new solar observing station on Mount Harqua Hala, Ariz., was 

 erected in July, 1920, at the expense of funds donated for the pur- 

 pose by Mr. John A. Roebling, of Bernardsville, N. J., and this 

 station has been occupied as a solar radiation observing station by the 

 Astrophysical Observatory since October, 1920. 



The present value of the buildings and equipment for the Astro- 

 physical Observatory, owned by the Government, is estimated at 

 $50,000. This estimate contemplates the cost required to replace 

 the outfit for the purposes of the investigation. 



WORK OF THE YEAR. 



At Washington. — The director, with Mr. Fowle and Mrs. Bond, 

 was engaged much of the year on the preparation and proof reading 

 of Volume IV of the Annals of the Observatory. This quarto 

 volume of 390 pages, including 60 illustrations and 118 pages of 

 numerical tables, covers the work of the years 1912 to 1920, and 

 was published in June, 1922. New apparatus and methods of ob- 

 serving are described and illustrated, and a large mass of solar 

 observations is presented and discussed. Evidence is given of many 

 kinds which indicates the solar variability. Reference is made tO' 

 applications of the results which have been made by several me- 

 teorologists. 



In preparation for work proposed for the expedition to Mount 

 Wilson in the summer of 1922, Mr. Aldrich, in consultation with. 

 104 



