OF RADIANT HEAT THROUGH DIFFERENT BODIES. 73 



this respect entirely diffei-ent from rays of light*. But they resemble 

 them in the property of refrangibility. This is completely proved by 

 means of the rock salt, the only diathermanous body that is capable of 

 transmitting the calorific rays emanating from every source. 



As to lenses and common prisms they refract a certain portion only 

 of the radiant heat; for the glass intercepts several sorts of calorific rays 

 issuing from sources at a high temperature, and absorbs nearly the whole 

 of the heat given out by bodies whose temperature is below incandes- 

 cence. To this circumstance it is that we must attribute the doubt 

 hitherto entertained as to the refrangibility of nonluminous heat. 



NOTE. 



[We annex to the foregoing papers of M. Melloni, various references 

 to other Memoirs on the Transmission of Radiant Heat, and to former 

 views of the results obtained by him. 



In the " Report of the Third Meeting of the British Association," 

 p. 381 , is an "Account of some recent Experiments on Radiant Heat," com- 

 municated by Professor Forbes, and reciting M. Melloni's Experiments ; 

 and also, p. 382, an abstract of his subsequent discoveries communicated 

 by himself to Professor Forbes, in order to be laid before the British 

 Association. 



The "Notices of Communications to the British Association atDublin, 

 August 1835," contains, p. 9, some remarks by Professor Powell on 

 Melloni's repetition of his original experiment described in the Philoso- 

 phical Transactions for 1825, and in the Philosophical Magazine, First 

 Series, vol. Ixv. p. 437, and a notice of Dr. Hudson's Experiments with 

 the Thermomultiplier, rendering it questionable, in his judgement, 

 whether the results obtained by Melloni on diathermanous bodies were 

 not attributable to conduction. These notices will also be found in the 

 London and Edinburgh Philosophical Magazine, vol. vii. pp. 296,298. 



Prof. Forbes's Memoir "0« the Refraction and Polarization of Heat" 

 is contained in the Transactions of the Royal Society of Edinburgh, 

 vol. xiii. p. 131, etseq.; and also in Lond. andEdinb. Phil. Mag., vol. vi. 

 p. 134, et seq. 



The following papers and notices have appeared exclusively in the 

 London and Edinb. Philosophical Magazine: 



A Note relative to the Polarization of Heat, by Professor Forbes 



• [Professor Forbee, however, in his Memoir, Lond. and Edinb. Pliil. Mag., 

 ▼ol. vi. p. 205, et seq., referred to in the Note which we liave annexed, has 

 established the fact of the polarization of rays of heat by this means, as well as 

 by those of refraction and reflexion. — Edit.] 



