OF RADIANT HEAT THROUGH DIFFERENT BODIES. 73 
this respect entirely different 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, isan “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 at Dublin, 
= 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 “On the Refraction and Polarization of Heat” 
is contained in the Transactions of the Royal Society of Edinburgh, 
vol. xiii. p. 131, e¢ seg.; and also in Lond. and Edinb. 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 Forbes, however, in his Memoir, Lond. and Edinb. Phil. Mag., 
ol. vi. p. 205, et seq., referred to in the Note which we have annexed, has 
tablished the fact of the polarization of rays of heat by this means, as well as 
y those of refraction and reflexion.—Enpir. | 
