42 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 'JJ 



RELATION OF SOLAR RADIATION AND WEATHER TO THE 

 POSITION OF SUN SPOTS 



Another line of research was to determine the relations between 

 solar variations and the spots and faculse on the sun. A preliminary 

 investigation had disclosed an apparent relation between the positions 

 of spots and the intensity of the heat radiation of the sun {Nature, 

 Vol. 107, 1921). In order to determine this relation as fully as 

 possible, all the available data were assembled. These consisted of 

 observations published by the Greenwich' Observatory from July, 

 1918, to December, 1921, of visual observations made at La Plata 

 and Pilar, Argentina, from January, 1921, to April, 1924, furnished 

 me by William Hoxmark, and of observations made in Canton, 



Table 12. — Mean Solar Radiation in Relation to Position of Sun Spots. 



Note: The values in the table are to be added to 1.900 so that the first value, for example, be- 

 comes 1.939. The number of cases of large spots on zero day was 114 and of all spots, 310. 



Massachusetts, from May to July, 1924, The day on which a spot 

 crossed the central meridian of the sun, as seen from the earth, was 

 called zero day, and the observed solar radiation values were tabulated 

 for each of the seven days preceding that date and also for each of 

 the twenty-two days following, thus covering a period of thirty days. 

 The large and small spots were tabulated separately, sums and means 

 were obtained, and then the sums of the two series were combined 

 for obtaining mean results for all spots which crossed the center of 

 the sun from July, 1918, to July, 1924, that is, during an interval 

 of six years. 



The Greenwich observations being arranged differently, means 

 were determined separately for the years 1918 to 1921, and 1922 to 

 1924, and a mean of the two sets of means was obtained. These means 

 of the observed solar radiation values are given in table 12. 



