282 



Hutchins and Pearson — 



-Air 



Radiation. 



warmed blackened 



tank gave 

 Table IV. 



the 



following del 



Temp, cold tank. 



Temp, hot tank. 



Deflections. 



20-56 



24-05 





106* 





24-10 





101-5 





24-18 





109-5 





24-22 





106-5 



20-58 



24-24 





104-5 



20-57 24-16 105-6 



The mean deflection corresponding to 1° excess temperature of 

 air is 



^ = 0-4472. 

 121-5 



The excess temperature of the lampblacked surface is 



24-16 — 20-57 + 0-59 = 4'18 



where +0'59 is the thermometer correction. Hence the deflec- 

 tion per degree excess for the lampblacked surface is 



105-6 



4-18 



25-26. 



Finally, the ratio of the hot air radiation to that from the 

 blackened surface is 



•4472 



= •01770. 



25-26 



On July 1, we obtained "159; on July 2, 0-177; on July 8, 

 0-1734; the average of six days being 0*1685. 



The absorbing column was then made 245 cm , 127 cm , 61 cm , and 

 30 cm , and the same method followed for each distance, in each 

 case the observations being distributed over several days. The 

 results are tabulated below : 





Table V. 





Absorbing 





Mean 



column 





Ratio 



30 cm 





•0332 



61 





•0278 



127 





•0195 



245 





•0169 



491 





•0168 



Plotting these observations with the numbers in the first 

 column of Table V as abscissas and the numbers in the second 

 column as ordinates, we obtain the following curve : 



