Hutchins and Pearson — Air Radiation. 



283 



Curve. U. 



Jirdejyth. 



300 



400 



SDO 



An inspection of this curve reveals a very important feature 

 of air radiation hitherto unknown ; namely, that some 60 per 

 cent of its own radiation is absorbed by a column as thin as 

 245 cm , the remaining 40 per cent being freely transmitted as 

 though coming from a black body. We have plotted the ratios 

 of air radiation to lampblack radiation per degree excess tem- 

 perature. The point where the curve cuts the Y-axis will 

 correspond to the ratio at zero depth of absorbing column, and 

 is important to know. This point may be calculated as follows : 



Let L= radiation from lampblack 



b= radiation of air for which absorption is neglected 

 J'= Characteristic radiation from hot air, that is, b neglected 

 Then at zero depth, b-\-J / is the total radiation from air. 

 Lambert's law is J=J'a h , and we have plotted the quantity 



— r — versus d. Taking ^=1, and d 2 = 2*033, we have 





b 



+ J, 



= 0*0332 = 



b 

 0*0278 = — 



I 



+ 

 L 



L 



J 2 _ 









b 



=r = 0'0L69 



b + 3'a 

 L ' 



* + J V-"* 



(1) 

 (2) 

 (3) 



We wish to find the value of (J+ J')/L. 

 From (3), b = 0*169 L 



whence, from (1), J'a = 0-0163 L 



and 



L/J' 



