RJiPORT OF THE SECRETARY. 25 



Saturn by Dr. Guthnick, of the Berlin-Babelsberg Observatory. Va- 

 riations in brightness of that planet were shown which were found 

 to be in almost exact correlation with variations of the solar radiation 

 on the earth as observed at Calama, Chile. This comparison indicates 

 that the variation of the solar radiation is due to rays from the sun 

 of unequal brightness, Avhich, rotating with the sun, strike the various 

 planets successively in the order of their longitudes, and fall one after 

 the other upon the earth as the sun by rotation brings them into line 

 with us. 



A new instrument for measuring nocturnal radiation, devised by 

 Messrs. Abbot and Aldrich and constructed at the observatory in- 

 strument shop, was successfully tried during the year. It is pro- 

 visionally called the " honeycomb pyranometer." The instrument is 

 almost as sensitive as a flat blackened strip and moreover, has the 

 valuable property of being fully absorbing, which a strip has not. 

 It is an instrument of great promise for standard measurements of 

 various kinds of radiation. 



Through the generosity of Mr. John A. Roebling, of New Jersey, 

 it was made possible to move the Smithsonian observing station pre- 

 viously located on the plain near Calama, Chile, to a near-by mountain 

 above the interference of dust and smoke. With the remainder of 

 Mr. Eoebling's grant, it is proposed to establish a new observing sta- 

 tion on the Harqua Hala Mountain in Arizona, on > of the most 

 cloudless regions in the world. The establishment of these two sta- 

 tions, so widely separated from one another, will make it possible 

 to obtain nearly ^very day in the year check observations of the solar 

 constant of radiation, laying a firm foundation of solar observa- 

 tions from Avhich meteorologists will be able to determine Avhether the 

 variations in the sun are of value, as present results indicate, in fore- 

 casting weather conditions. However, with the limited funds at his 

 disposal. Dr. Abbot found it necessary to transfer apparatus from the 

 Mount Wilson station to the new Harqua Hala station, and he urges 

 in his report that Congress appropriate sufficient money to provide 

 for independent observing equipment for both stations and for 

 needed improvements to the Arizona station. 



INTERNATIONAL CATALOGUE OF SCIENTIFIC 

 LITERATURE. 



The United States Regional Bureau of the International Catalogue 

 of Scientific Literature is intrusted with the duty of collecting, in- 

 dexing, and classifying titles of all scientific papers published in 

 the United States to form part of the International Catalogue issued 

 by a central bureau in London. 



