284: Hutchins and Pearson — Air Radiation. 



Substituting the values of a and h in (2), we get 



3 



(0-0163 L) 2 - c 

 0-0109 L = y (jrydir 



whence J' = iT (^^f* 



L 0-0109 J 



This gives = 0-0409. 



This point fits in a perfectly satisfactory manner upon a 

 smooth curve drawn through the observed points. 



What the course of absorption may be beyond a depth of 500 cm , 

 we have no means at present of judging. It may be suggested 

 that the compound nature of air is responsible for its peculiar 

 manner of absorption. Perhaps its contained water vapor is 

 the substance radiating like a black body, and that apart from 

 this, the strongly curved portion of our diagram shows the 

 characteristic behavior of its prominent gaseous constituents. 

 If this be true, it follows that the radiation of pure dry air is 

 effective only at comparatively slight depths. The amount of 

 moisture in the air during this course of experiments was con- 

 siderable, the relative humidity not varying much from 78*2. 

 It may be that water vapor so little removed from its point of 

 saturation no longer behaves as a true gas, but as an aggregate 

 of particles, in which case it would transmit all rays with consider- 

 able freedom, the particles producing a scattering effect merely. 

 The accepted explanation of the color of the sky favors this 

 view. 



We have now to discuss the change of radiation of air with 

 change of temperature. By introducing a variable resistance 

 into the circuit of the heating box the temperature of the 

 heated air could be changed at will. A mean of five to ten 

 consistent observations was taken for each temperature and 

 the results tabulated as follows : 





Table VI. 





Exc. Temp. 





Mean Defi. 



22-5 





18-55 



28-2 





24-9 



43-2 





40-9 



72-1 





77-9 



87-0 





105-7 



125-5 





185-9 



Plotting deflections versus temperatures from Table YI, we 



obtain the following curve : 



