REPORT OF THE SECRETARY. 23 



and renewed again on June 11, 1911, which tend to confirm the con- 

 clusion that the sun's output of radiation varies from day to day in 

 a manner irregular in period and quantity. Assurance seems now 

 complete that this latter result will be tested during the next fiscal 

 year by long-continued daily observations taken simultaneously at 

 two widely separated stations, where the atmosphere is believed to be 

 specially favorable for such research. The definite determination of 

 the laws governing the apparent variability of the " solar constant " 

 it is expected will be of much value in the probable forecast of 

 climatic conditions from year to year. 



Measurements have also been made of the transparency, for long 

 wave radiation, of columns of air containing known quantities of 

 water vapor. This line of research promises highly interesting results. 



As mentioned on another page, arrangements have been made with 

 several observatories, widely separated through the world, for the 

 use of the standard silver-disk secondary pyrheliometer designed by 

 the director of the Smithsonian Astrophysical Observatory. It is 

 hoped to thus secure not only uniformity of radiation measures, but 

 also a more exact knowledge of solar radiation and the influence of 

 the terrestrial atmosphere upon it. 



INTERNATIONAL CATALOGUE OF SCIENTIFIC 

 LITERATURE. 



The International Catalogue of Scientific Literature publishes, 

 through the cooperation of countries in all parts of the world, a 

 current classified index to the literature of science. Seventeen volumes 

 have been published annually, beginning with the literature of 1901. 

 The organization consists of a central bureau in London and regional 

 bureaus established in and supported by the 32 countries taking part 

 in the enterprise. Supreme control of the catalogue is vested in an 

 international convention, which met in London July, 1905, and July, 

 1910, and is to meet every tenth year hereafter. The second inter- 

 national convention met in London at the rooms of the Royal Society 

 on July 12 and 13, 1910, and Mr. Leonard C. Gunnell, assistant in 

 charge of the United States regional bureau, was sent by the Insti- 

 tution as the delegate from the United States. The convention de- 

 cided that on account of the success already achieved by the Interna- 

 tional Catalogue and the great importance of the objects promoted, 

 the enterprise would be continued. Attention was called to the ur- 

 gent need of a permanent fund to aid in carrying on and extending 

 the work. It was pointed out that although various regional bureaus 

 for the collection of material were supported by the countries in 

 which they were located, the maintenance of the central bureau for 

 general administration and actual publication of the 17 annual vol- 

 umes was dependent entirely on the funds derived from the sub- 



