NO. 5 



SOLAR VARIATION AND FORECASTING ABBOT 



II 



the hypothesis of solar variation is in the field. When, however, we 

 take Mount Wilson and Calama data of identical dates, as in figure 8, 

 they show no such variance. Figure 8 gives all comparable daily 

 values of 1918, 1919, and 1920. Except for the greater number 



Fig. 7. — Monthly mean observations at Mount Wilson, 

 1905-1917. The heavy smoothed curve and stars near it 

 represent Prof, Marvin's determination of the yearly perio- 

 dicity in solar radiation, as indicated by the scale at the upper 

 right-hand corner of the diagram. 



of poor results at Mount Wilson, the agreement is good and yields 

 a correlation coefficient of about 50 per cent. 



There is another objection to using the mean results of the 15 

 years as Professor Marvin has done. The numerous values of the 

 months June, July, August, and September, which have fixed the 



