110 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Spectro photometric Measurements upon Rods with Treated Surfaces. 



In order to compare the radiation of rods of black surface with those 

 the surfaces of whicii have acquired a gray coating by treatment in 

 hydrocarbon vapor, rods were mounted in the usual manner, and after 

 the exhaustion of the air from the metal box, gasoline vajDor was allowed 

 to enter until the atmosphere surrounding the rod was saturated. The 



Figure 21. 



rod was then brousiht several times to a \\\s\\ state of incandescence for 

 a few seconds at a time, by which means the entire surface became coated 

 with a gray deposit of carbon similar to that obtained by tlie treatment 

 of incandescent lamp filaments. The metal box was then again pumped 

 out and spectrophotometric measurements similar to those already de- 

 scribed were made upon the radiation from the treated surface. It was 

 thouo-ht that as the result of this treatment the carbon rod"^ would stand 



