32 



Messrs. W. E. Wilson and P. L. Gray. On the 



The radiation is calculated from the formulae given on p. 31, for 

 temperatures 600, 700 .... 1200 abs. ; the fourth column gives the 

 ratio black/ bare. 



Table III. Ratio of Emissive Powers of Black and Bare Platinum. 



600 



700 



800 900 1000 s 



Temperature. 



MOO' 



FIG. 4. Curve showing the ratio of the emissive powers of blacked and bare 

 platinum at different temperatures. 



The curve (fig. 4) shows the same results graphically. 



It will be seen at once that the ratio diminishes as the temperature 

 increases, but less and less rapidly. The observations agree fairly 

 well with the old experiments generally described in the text-books 

 experiments made at 100 C. and thereabouts in which the ratio 



