of Energy in the Spectra of Sol 



435 



the more general formula (10), can only be considered as a 

 first approximation ; that these equations have been deduced 

 for solid bodies, and not for such bodies as the sun ; and, 

 lastly, that in our atmosphere, as well as in the colder regions 

 of the gas surrounding the sun there must occur the pheno- 



Fiff. 4. 



menon of degradation of the radiant energy. In consequence 

 of this effect, which has not been eliminated by Prof. Langley, 

 a portion of the more refrangible radiations would be trans- 

 formed into longer undulations, which would tend to modify 

 the spectral diagram exactly in the sense indicated by obser- 

 vation. 



Recognizing the provisional character of the ideas suggested 

 in this paper, I hope that it will be possible to give them a 

 greater development and precision when once we are in pos- 

 session of more complete experimental data to guide us in this 

 study. We should then be able to express by one sufficiently 

 exact formula the law of distribution of radiant energy as a 

 function of the wave-length and the temperature of the source. 

 Such a formula would be of great service in all questions 

 arising in the study of spectra. 



