NO. 5 



SOLAR VARIATION AND FORECASTINC 



-ABBOT 



21 



1924. Mean Mount Wilson values, grouped with gradually increasing 

 spot numbers, are given by crosses. Modern values of 1918 to 1924 

 from Montezuma and Harqua Hala observations are indicated by 

 circles. Evidently higher solar constants are associated with greater 

 solar activity. Some of the irregularities of the data are probably 

 due to the comiteracting tendency associated with crossing of the 

 sun's central meridian by spots, as will be mentioned below. 



1.97 



1.96 



I.9S 



1.94 



IJ93 



IS2! 



O 20 40 ^O §0 70S 120 I40 76(3 JSO 705 2-?0" 



Fig. 13. — Increased sun-spot activity brings higher solar-constant vahies. 



My colleague, Mr. Fowle, has compared the results published by 

 the Observatory of Ebro on areas of sun spots and of flocculi with 

 our solar-constant values of 192 1- 1923. Figure 14 shows these 

 relations. It is clear that a fairly close connection appears between 

 flocculi and solar constants, closer than prevails between sun spots 

 and solar constants. The extraordinary drop from 1921 is confirmed. 



Solar changes of short period also accompany observed changes 

 in the sun's visible appearance. 



In the summer of 1923, being at the Mount Wilson Observatory, 

 Director W. S. Adams and I took all the simple photographs of the 

 sun which had been made there from August, 191 8. to July, 1920, 



