32 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1916. 



After several years of experimenting the Astrophysical Observa- 

 tory has constructed an instrument called the pyranometer, designed 

 for measuring the intensity of sky light by day and of radiation 

 outward toward the sky by night. A full account of this instrument 

 has been published in pamphlet form. The pyranometer may prove 

 of advantage in botanical investigations in forests and greenhouses, 

 since it can measure radiation in deep shade as well as in the full sun. 



The Institution has made an allotment from the Hodgkins fund 

 for carrying on solar-constant work at some suitable place in South 

 America. Throughout the year, for several years, it is intended to 

 continue observations at Mount Wilson in California and at the 

 South American station with a view to determine the dependence of 

 the earth's climatic conditions on the sun's variation of radiation. In 

 addition to his solar-constant work the director of the observatory 

 has given considerable attention to experiments at Mount Wilson 

 with solar cooking apparatus " comprising ovens heated by oil under 

 gravity circulation maintained by heat collected by a concave cylin- 

 dric mirror of about 100 square feet surface." These experiments 

 were not concluded at the close of the year. 



INTEENATIONAL CATALOGUE OF SCIENTIFIC 

 LITEKATURE. 



The International Catalogue of Scientific Literature, the United 

 States bureau of which is administered by the Smithsonian Institu- 

 tion, was organized in 1901, and since that date 17 volumes of refer- 

 ences to scientific literature, one for each of 17 branches of science, 

 have been published each year. During the past year 24,160 classi- 

 fied references to American scientific literature were prepared by the 

 United States bureau, bringing the total number of references to the 

 literature of this country since the inception of the' catalogue up to 

 369,509. 



As stated in last year's report, the war in Europe caused consid- 

 erable financial embarrassment to the publication of the catalogue 

 owing to the impossibility of collecting subscriptions from several of 

 the countries involved. The generosity of the Royal Society of Lon- 

 don in making up this loss of income made possible the publication 

 of the thirteenth annual issue, and this year a request was made for 

 assistance from the United States. Your secretary succeeded in in- 

 teresting the Carnegie Corporation, of New York, in the project 

 and through the generous assistance of that establishment it was 

 made possible to publish the fourteenth annual issue. 



The value to science of this catalogue is universally recognized, and 

 it is the opinion of scientists everywhere that any lapse in its publi- 

 cation would be a real calamity, as shown by the action of the Inter- 



