SOLAR RADIATION ABBOT 



191 



States. Figure 14 shows, at A and C, curves representing 5-month 

 consecutive means of the observed departures from normal of the 

 monthly mean temperature of Washington, and of Williston since 

 1918. Curves B and D show 5-month consecutive means of repre- 

 sentations of these temperature departures as the sum of periodicities 

 of 68, 45, 25, 11, and 8 months, which T think we may now attribute 

 to solar variation. However, in addition to these five periodicities, 



Figure 14. — Solar periodicities reflected in temperatures of Washington and Williston 



E, F, G, H, I, periodicities of 68, 45. 25, 18, and 11 months in the temperature of 

 Williston, N. Dak. D, their summation, and C the departures from normal temper- 

 ature, hoth smoothed by 5-month consecutive means. B and A, similar smoothed 

 curves for Washington temperature departures. 



I found it necessary to include for both stations an important 

 periodicity of 18 months' interval which therefore seems to be a 

 wide-ranging terrestrial contribution. At Williston, in addition to 

 all these, I found inconspicuous periodicities of 5, 3.6, and 3 months. 

 It seems to me very interesting to trace the similarities and the dis- 

 similarities of march of the curves A and C, wherein long-continued 

 pronounced departures from the mean temperatures stand out so 

 conspicuously. 



