KIMBALL: NORMAL ATMOSPHERIC TRANSPARENCY 



19 



larger than the ratios of column 6, which are derived from mean 

 radiation values. Actually, however, the averages of columns 6 

 and 7 are practically in accord for 1912, omitting the ratios for 

 May 1 to June 9, inclusive, while for 1913 the average of column 

 7 exceeds the average of column 6 by about 5 per cent. 



TABLE 1 



Monthly Summary of Solar Radiation Intensities with the Sun at Zenith 

 Distance 60°. Mount Weather, Va. 



1912 



May 1-June 9 



June 10-30 



July 



August 



September 



October 



November 



December 



1913 



January 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



a. m. 



p. m. 



MAXIMUM 



a. m. 



p. m. 



Gram calories per min. per cm^ 



RA- CURRENT 



TIO AVERAGE 



1.06 

 0.86 

 0.86 

 0.73 

 0.80 

 0.81 

 0.90 

 0.97 



0.90 

 0.91 

 0.85 

 0.79 

 0.87 

 0.89 

 0.88 

 0.93 

 0.95 

 0.87 

 0.94 

 1.01 



1.15 

 0.86 

 0.77 

 0.70 

 0.81 

 0.91 

 0.88 

 1.01 



0.93 

 0.94 

 0.94 

 0.95 

 0.92 

 0.93 

 0.86 

 0.96 

 0.99 

 0.94 

 0.97 

 1.08 



MEAN 

 RATIO 



1.10 

 0.86 

 0.81 

 0.71 

 0.81 

 0.86 

 0.89 

 0.99 



0.92 

 0.93 

 0.89 

 0.87 

 0.90 

 0.91 

 0.87 

 0.95 

 0.97 

 0.91 

 0.96 

 1.04 



The last column of Table 1 is simply the average of the two 

 preceding columns. It is believed that it gives a close approxi- 

 mation to the monthly means of the relative intensity of solar 

 radiation for the period under consideration, as compared with 

 the intensity under normal conditions for the respective months. 

 These relative intensities, together with intensities for Madiso:i, 



