EEPOET OF THE SECRETARY. 33 



THE ASTEOPHYSICAL OBSERVATORY. 



The Astrophysical Observatory continued during the past year 

 the important investigations begun during the administration of the 

 late Secretary Langley to determine the solar constant of radiation 

 and the variability of the sun. In his account of the operations of 

 the observatory on another page of this report Director Abbot dis- 

 cusses the results of these researches up to the present time and con- 

 cludes that the observations at Bassour, Algeria, taken in connection 

 with those made simultaneously at Mount Wilson, Cal., have estab- 

 lished the variability of the sun. He concludes also that a variability 

 connected with the sun-spot cycle has been shown. 



Observations were also made to determine the effects of volcanic 

 eruptions on climate. Soon after the eruption of Mount Katmai, 

 Alaska, in June, 1912, the presence of dust in the upper air from this 

 volcano was indicated both in California and in Algeria, and in 

 August the direct radiation of the sun was found to be reduced about 

 20 per cent by the interposition of the dust cloud. Mr, Abbot and 

 Mr. Fowle discuss the results of their observations and the general 

 subject of " Volcanoes and Climate " in a paper in the Smithsonian 

 Miscellaneous Collections. They conclude that a combination of 

 the effects of sun spots and volcanic haze accounts for all the prin- 

 cipal irregularities in the temperature of the earth for the last 30 

 years. 



In connection with observations on nocturnal radiation it became 

 necessary to determine the temperature and humidity prevailing 

 above certain stations. This was accomplished with the cooperation 

 of the United States Weather Bureau through the use of sounding 

 balloons and captive balloons carrying to high altitudes self-record- 

 ing apparatus for measuring the temperature, pressure, and 

 humidity of the air. 



There was completed during the year volume III of the Annals 

 of the Astrophysical Observatory, recording the work accomplished 

 from 1907 to 1913. 



INTERNATIONAL CATALOGUE OF SCIENTIFIC 

 LITERATURE. 



There is administered by the Smithsonian Institution through a 

 small annual appropriation by Congress, the United States Bureau 

 of the International Catalogue of Scientific Literature. This is 

 one of the 33 regional bureaus whose function it is to collect, index, 

 and classify all scientific publications of the year in each country and 

 to send the classified references to the central bureau in London, 

 where, since 1901, they have been collated and published in a series 



