PHYSICAL METABOLISM 245 



The experiment I have described, however, suffi- 

 ciently proves that the fluorescent light itself has 

 not this action upon its own radiation, and therefore 

 when the light absorbed is the same as the fluor- 

 escent light itself, the effect observed is really a case 

 of a change of absorption and not merely of a 

 diminution in the brightness of the fluorescent 

 light. 



In endeavouring to repeat my experiments on 

 the change of absorption produced by fluorescence 

 of uranium glass, M. CamichaeP adopted a method 

 which from its nature was rather too loose to 

 enable one to detect the effect sought ; but his 

 negative result is of interest in so far as it gives 

 an indirect confirmation of my previous work on 

 the subject. He appears to have been much im- 

 pressed by the circumstance that when the source 

 of the transmitted light is a flame, as in his experi- 

 ments, of a petroleum lamp, the more refrangible 

 rays increase the fluorescence and thus the coefficient 

 of transmission is diminished, and he has since then 

 taken precautions to prevent this. As, however, it 

 is a matter of diff"erences, there is no need to lay 

 much emphasis upon this point, and the results 

 obtained by Messrs. Nichols and Merritt^ very 

 satisfactorily prove that the increased fluorescence 

 does not prevent the effect of the change of 

 absorption from being observed. In my own ex- 

 periments, it was the absorption of the fluorescent 



1 Comptes Bendus, Jan. 16th, 1905. 



2 Physical Beview, Dec, 1904. 



