OF RADIANT HEAT THROUGH DIFFERENT BODIES. 3*7 



the different luminous rays, and thus throws certain quantities of heat 

 on the very spaces occupied by the different colours of the spectrum ; 

 but that in the coloured glasses and, generally, in bodies more or less 

 diathermanous, the absorbent force does not act in the same manner as 

 the force of refraction, which sometimes extinguishes more heat than 

 light and at others more light than heat. 



But those who maintain the identity of the two agents will reply, that 

 the differences observed in the calorific and luminous transmissions of 

 the diaphanous or coloured media are produced by rays of obscure 

 heat which mix inr great quantities with the rays of light emitted by 

 the flame. 



In order to decide how far it is allowable to maintain the one or the 

 other hypothesis, we should have data which, at present, are not within 

 our reach. We shall resume this subject at the end of the next Memoir, 

 and conclude the present one with an account of a very remarkable ap- 

 plication of the numerical results contained in the foregoing tables. 



It had been established by the beautiful experiments of Seebeck that 

 the place of the maximum of temperature in the solar spectrum varies 

 with the chemical composition of the substance of which the prism is 

 made. This eminent philosopher observed that the highest degree of 

 heat which, in the spectrum furnished by a prism of ci'own glass, was 

 in the red, passed to the orange when the prism employed was a hollow 

 glass one filled with sulphuric acid, and was found in the yellow when 

 the same prism was filled with pure water*. 



I discovered some months since that the caloric rays scattered on the 

 colours given by a common prism do not undergo the same alteration 

 in passing through a layer of water ; the loss varies inversely as the re- 

 frangibility, so that the most refrangible rays pass undiminished and the 

 least refrangible are entirely stopped by the liquid f . 



This experiment led to a very simple explanation of the results ob- 

 tained by Seebeck. 



The solar heat which presents itself to the anterior face of the prism 

 of water contains rays of everj' degree of refrangibility. Now the ray 

 which has the same index of refraction as the red light, suffers in pass- 

 ing through the prism a loss porportionally greater than the ray which 

 possesses the refrangibility of orange light, and less is lost by the latter 

 in the passage than by the heat of the yellow ray. These increasing 

 ratios in the losses of heat sustained by the less refrangible rays have 

 an evident tendency to transfer the maximum to the violet. It may 

 therefore be stopt at the yellow. 



• Schweiggcr's Jakrbuch der Chemie und Physik, vol. x. [A translation of 

 the memoir of Seebeck here referred to will be found in the Philosophical Ma- 

 gazine, first scries, vol. Ixvi. p. 330, el seq. — Edit.] 



t ylnnales de Chimie el de Physique, Deccmbrc 1831. 



