REPORT OF THE SECRETARY. 25 



was brought nearly to completion. A large amount of delicate 

 instrument work was carried out at the observatory instrument 

 shop, and Dr. Abbot was invited by Dr. 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 

 Wilson, 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 TO 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- 

 ture of 1901, the catalogue has been completed through 1914, and 

 there is now on hand much material from that date up to the present 

 time. 



Until the beginning of the late war the catalogue was practically 

 self-supporting, but owing to the international chaos caused by the 

 war the finances of the enterprise are now in a very precarious 

 condition. For this reason the Roj^al Society of London, the finan- 

 cial sponsor of the catalogue, called a conference which was held 

 in London during September, 1920. At this conference delegates 

 were sent from 13 of the principal countries of the world, exclusive 

 of the enemy countries, who were not included in the Royal Society's 

 invitation. The United States was represented by delegates from 

 the National Academy of Sciences, the National Research Council, 



