REPORT OF THE SECRETARY. 21 



ASTROPHYSICAL OBSERVATORY. 



The most important event during the year was the location of a 

 new solar observing station on Mount Harqua Hala, Ariz., probably 

 the most cloudless region in the United States. This station, which 

 was erected through the generosity of Mr. John A. Roebling, of New 

 Jersey, will be used for the purpose of securing solar-constant obser- 

 vations on all possible days for several years, which it is hoped will 

 furnish, in conjunction with similar observations to be made at the 

 Smithsonian station at Montezuma, Chile, a sound basis for the study 

 of the relation between solar variation and our weather conditions on 

 the earth. 



At Washington the preparation of Volume IV of the Annals of the 

 Astrophysical Observatory, mentioned in last year's report, was 

 brought nearly to completion. A large amount of delicate instru- 

 ment work was carried out at the observatory instrument shop, and 

 Doctor Abbot was invited by Doctor Hale, of the Mount Wilson Solar 

 Observatory, to prepare a special spectrobolometer to observe the 

 energy spectra of the stars. This extremely delicate apparatus was 

 nearly completed at the close of the year. 



In the field the usual solar observations were conducted at Mount 

 AVilson, Calif.; Montezuma, Chile; and at the new station in Ari- 

 zona. At Mount Wilson Dr. Abbot and Mr. Aldrich also carried 

 on observations on the distribution of radiation over the sun's 

 disk, and various investigations with the pyrheliometer, the spectro- 

 bolometer, the pyranometer, and the Angstrom pyrgeometer. The 

 solar cooker, on which Dr. Abbot has been working for several 

 seasons, was brought to perfection, and practically all the cooking 

 operations required by the observers were performed with the 

 apparatus. 



At the new Arizona station observing was begun about the middle 

 of September, and from then until February conditions were even 

 better than had been hoped for. It was possible to make observa- 

 tions on about 70 per cent of the days during that period. March, 

 April, and May were less satisfactory, but this was apparently due 

 to the unusual character of the weather all over the world, and it is 

 confidently hoped that continued observations of the sun here and 

 at the Chile station will lead to important results bearing on weather 

 prediction on the earth. 



INTERNATIONAL CATALOGUE OF SCIENTIFIC LITERA- 

 TURE. 



This international cooperative enterprise has been in' existence 

 since 1900, having as its object the systematic indexing and classify- 

 ing of all original scientific publications. Beginning with the litera- 

 101257—22 3 



