NO. 29 



VOLCANOES AND CLIMATE — ABBOT AND FOWLE 



values which would have obtained if the sun had been at 48 from 

 the zenith (air mass 1.5) and if the earth's distance from the sun 

 had been at its mean value. The remaining- columns of the table 

 give the vertical transmission coefficients x at different wave-lengths 

 in the spectrum. The values in the first line, corresponding to May 

 and early June, are in close accordance with similar values obtained 

 in former years when the atmosphere was of normal transparency. 

 Accordingly the values in subsequent lines indicate by comparison 

 with the first line the average effect of the volcanic dust in diminish- 

 ing the transparency of the air. 



Early June . . 

 Late June . . . 



July 



August 



Haziest days 



.960 



.955 

 .9.38 



.931 

 .876 



BASSOUR, ALGERIA. 



Early June p. 72 



Late June I0.71 



J»iy 



August 



Haziest days . . . 



.947 



• 955 

 .904 

 .895 

 .872 



1 The values in this column give the ratios of the pyrheliometer readings at a solar zenith 

 distance 48°(air mass 1.5), and reduced to mean solar distance, compared to the solar constant 

 of radiation, taken as 1.93 calories per sq. cm. per minute. 



2 The values in these columns give the transmission coefficients for the wave-lengths named 

 for celestial bodies in the zenith (air mass 1.0). 



In further illustration of the effect of the haze we give Table 2, 

 which is computed to represent the condition of the solar radiation 

 transmitted obliquely through the atmosphere, at a solar zenith dis- 

 tance of about 48 (corresponding to air mass 1.5) . In the first column 

 are given the mean values of the total radiation per square centi- 

 meter per minute. In the second and third columns respectively, are 

 the fractions transmitted and the fractional decrease in the intensity 

 of the total solar radiation in passing from the outside of the atmos- 

 phere to the surface of the earth. The remaining columns give the 



1 By vertical transmission coefficient we mean the fraction of the intensity 

 of a beam of rays from a celestial body in the zenith which reaches the ground. 



