280 



Ilutchins and Pearson — Air Radiation. 



The sensitiveness of the instrument was changed by with- 

 drawing the condensing mirror at the point marked by the 

 horizontal line through the table. To reduce all to a common 

 scale, we need a reduction factor for change of sensitiveness. 

 This will be the ratio of the deflection per degree excess for 

 12 0, 79 to the deflection per degree for 12°*18, assuming that 

 the radiation rate is the same for these two near temperatures. 

 After applying this factor and dividing each deflection by 

 its corresponding temperature, we obtain the following: 



Table II. 



Excess Temp. Defl. per Deg. Exc. 



4-06 

 6-62 

 9'55 

 12*79 

 20-91 

 30-60 

 40-90 

 50-00 



15-42 

 15-63 

 17*07 

 17-51 

 18-61 

 20-01 

 20-23 

 20-86 



M'Farlane gives a table* showing the radiation in small 

 calories per second per square centimeter of a blackened sur- 

 face. For 50° excess, M'Farlane's figure is -000326. Multiply- 



ing the number in the second column of Table II by such a 

 factor as will reduce the last to -000326, we plot a curve 

 with excess temperatures as values of x, and the observed 

 radiation rates, derived as above, as values of y, and along 

 with it, a second curve from M'Farlane's observations. 



*Proc. Eoy. Soc, 1872, p. 93. 



