286 Tlutchins and Pearson — Air Radiation. 



Dist. 



Table VII. 



Defi 



5-0 





155 



4-0 





155 



3'0 





155 



2*0 





155 



1-0 





149 



0'5 





124 



0-2 





105 



o-o 





90 



0-2 





75 



0-5 





50 



1-0 





22 



The air flowing up past the outside of the warmed box gave 

 the deflections for negative values of distance ; the integral of 

 these was nearly sufficient to balance the loss for less tempera- 

 ture within the range of positive values of the distance. By 

 plotting a curve and integrating the positive and negative 

 values with reference to distance, and radiation rate as derived 

 from Curve III, we find the actual air column to be 0*967 as 

 effective as a column 10 cm deep, and at a temperature measured 

 at its center. 



We are now prepared to calculate the radiation constant, 

 h. Assume that this is wanted for an excess temperature of 

 100°, a depth of l cm , and zero absorbing column. We have : 



Ave. of all exc. air temps, observed = 122 c 

 Defl. for 122° from Curve III = 179 



a u 100 o „ a u _ 130 



Bad. per deg. from lampbl. at 4° exc. (avg.) = -000249 (M'Farl.) 

 Ratio of air to lampblack radiation for zero 



absorbing column, from Curve II, = '041 

 Therefore h = (130/179) (-000249) (0'1) ('041; (0-967) 



= 0*000000717 water-gram-degrees per sq. cm. 

 per sec. per deg. exc. temp. 



For 1°, this becomes 0*000000264, and may be found with 

 great facility from the curves given, or from their equations, 

 for any temperature or depth of absorbing column within the 

 limits of our observations. 



If our surmise be correct that the freely transmitted part 

 of moist air radiation is from its contained w r ater vapor, 

 amounting 1 to 40 per cent of the whole, then the above numbers 

 would become for dry air, 0*00000043 and 0*00000016, respec- 

 tively. 



Bowdoin College, July, 1904. 



