MEMOIR XXVIII.] DISTRIBUTION OF HEAT IN THE SPECTRUM. 39 1 



ures, unless the fixed lines be resorted to as standard 

 points. 



(2.) A ray which has passed through a solution of 

 sulphate of copper and ammonia possesses no insignifi- 

 cant heating power. I took a stratum of a solution of 

 that salt, of such strength that it only permitted waves 

 to pass which are of less length than 4860. Seen in the 

 spectroscope, the colors transmitted through it com- 

 menced with a thin green fringe, followed by blue, in- 

 digo, violet. It therefore gave rays in which, according 

 to the accepted views, little or no heat should be detect- 

 ed. Yet I found that such rays produced one ninth of 

 the heat of the solar beam. Does not this indisputably 

 show that the more refrangible rays have a higher ca- 

 lorific power than is commonly imputed to them ? 



(3.) Again, by the use of the apparatus presently to 

 be described, I found no difficulty in recognizing heat in 

 the violet region. But in the mode of conducting the 

 experiment heretofore resorted to, it could not be detect- 

 ed in rays more refrangible than the blue. It was this 

 result which gave so much weight to the conclusion, that 



O O ' 



in the more refrangible regions the calorific power is re- 

 placed by chemical force, and strengthened the idea com- 

 monly entertained that the solar radiations consist of 

 three distinct principles heat, light, and actinism. In 

 the Memoir above referred to, as soon to be published, I 

 shall present some facts which apparently make this view 

 indefensible. 



(4.) If waves of light falling upon an absolutely black 

 surface, and becoming extinct thereby, be transmuted 

 into heat, if the warming of surfaces by incident light 

 be nothing more than the conversion of motion into 

 heat an illustration of the modern doctrine of the corre- 

 lation of forces, heat itself being only " a mode of mo- 

 tion" it would seem extraordinary that the conversion 



