80 ANNITAL REPORT S^^THSO^s'IAN INSTITUTION, 194 2 



own radiation observations at widely separated stations but by com- 

 parison of them with the publications of visual and photographic 

 studies of the sun's surface made at other observatories. Such com- 

 parisons show, for instance, that the rotation of the sun upon its 

 axis in the approximate period of 27 days frequently is attended by 

 1 percent change in solar radiation associated with well-marked 

 changes in the visual and photographic appearance of the sun. 



The variation of the sun is shown not to be of uniform percentage 

 for all colors and wave lengths, but to increase rapidly in percentage 

 toward the shorter wave lengths of the violet and ultraviolet rays. 

 For ultraviolet rays of wave length 3500 angstroms, the percentage 

 variation is 6 times as great as for the solar radiation as a whole. 



Fourteen simultaneously operative regular periodicities are found 

 in solar radiation ranging from 8 months to 273 months in periods. 

 Each of these is reflected in temperatures and precipitations recorded 

 by meteorological observations of official weather services. Long 

 records, extending for 140 years, like those of Copenhagen, Vienna, 

 and New Haven, prove that the 14 solar periodic variations have 

 continued in unchanged phases, though perhaps not in unchanged 

 amplitudes, during all that interval. Assuming that the phases will 

 continue unchanged, and the amplitudes will be the average of 

 amplitudes since 1920, a prediction of the solar variation to 1945 is 

 hazarded. 



The publication of volume 6 of the Annals, in such beautiful form 

 and at so early a date, was made possible by funds generously sup- 

 plied by Mr. John A. Koebling. Without his long-continued and 

 munificent support and advice, the research could not have reached 

 this satisfactory fruition. It is greatly hoped that it will furnish 

 valuable aids to the science of meteorology. 



TBANSFEE OF THK DIVISION OF RADIATION AND OBGANISMS 



A second outstanding event of the year is the acceptance by the 

 Bureau of the Budget and the Congress of the proposal, strongly 

 recommended by the Regents of the Institution, that the Division of 

 Eadiation and Organisms, hitherto for 13 years supported by private 

 funds, and hitherto concerned with the fundamental study of plant 

 growth, be incorporated as a branch of the Astrophysical Observa- 

 tory. Since the beginning of the fiscal year 1942, this interesting 

 fundamental research has been supported by Congressional appropria- 

 tions, and its staff has been a part of the Government Civil Service. 



INSTRUMENTS 



Our detailed studies of the observations of the solar radiation 

 disclosed, as above said, that the percentage variation of the intensity 

 of the sun's rays is six times as great for ultraviolet rays as for the 



