NO. 4 SOLAR RADIATION ABBOT, FOWLE, AND ALDRICH 



From the foregoing the reader may see that the soundness of the 

 theory of the atmospheric extinction of radiation employed by us is 

 supported by the fact that its application to observations made under 

 widely diverse conditions yields nearly identical values of the inten- 

 sity of solar radiation outside the atmosphere. Nevertheless, it is 

 maintained by some critics that our estimate of the atmospheric 

 extinction is less than half large- enough. It seems very singular 

 that a grossly erroneous theory, according to which, however, the 



Fig. i. — Illustrating Atmospheric Extinction on a Clear Day and on a 



Hazy Day. 



Curve a, Bassour, June 9, 1912. Air-Mass, 1.5. 



Curve b, Bassour, June 9, 1912. Air-Mass, 3.5. 



Curve c, Bassour, July 26, 1912. Air-Mass, 1.6. 



Curve d, Bassour, July 26, 1912. Air-Mass, 3.5. 



transmission coefficients of the atmosphere for green light are found 

 to vary in different circumstances from 0.63 to 0.92, should neverthe- 

 less correlate its errors in such a way that all these diverse values of 

 transmission coefficients should lead to equal values of the intensity 

 of solar radiation outside the atmosphere. 



In further support of our values of atmospheric transmission, we 

 call attention to their connection with Lord Rayleigh's theory of the 

 scattering of light by molecules and particles small as compared with 

 the wave length of light. According to this the exponent of scatter- 

 ing varies inversely as the fourth power of the wave length, and thus 



