NO. 9 PERIODICITY IN SOLAR VARIATION ABBOT AND BOND 



It will be noted that the three stations not only agree closely, but 

 unite to indicate fluctuations of the sun's emission. The extreme range 

 of variation shown in Figure i is 1.2 per cent. On an earlier occasion, 

 in 1922, a range of the monthly mean values of nearly 3 per cent was 

 observed as indicated in Figure 2, where values from Montezuma, 



Fig. 3. — Solar variation, 1920-1930, composed of seven regular periodicities of 

 7, 8, II, 21, 25, 45, and 68 months interval, respectively. A, original data; C, 

 8-month; D, ii-month; E, 25-month; F, 45-month; G, 68-month; H, 7 and 

 21-month ; B, residual after removing all periodicities. 



Chile, and Harqua Hala, Ariz., are compared. Taking the best results 

 of the work as derived from the evidence of all stations, we find the 

 variation of monthly mean solar-constant values since 1920 as indicated 

 in Figure 3, curve A. We are able to reproduce it as the sum of seven 

 regular periodicities of 7, 8, 11, 21, 25, 45, and 68 months. The degree 



