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Rh 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 incandescence. To this circumstance it is that we must attribute the doubt hitherto entertained as to the refrangibility of nonluminous heat.

[ 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," communicated 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, August 1835," contains, p. 9, some remarks by Professor Powell on Melloni's repetition of his original experiment described in the Philosophical Transactions for 1825, and in the Philosophical Magazine, First Series, vol. lxv. 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 "0n the Refraction and Polarization of Heat" is contained in the Transactions of the Royal Society of Edinburgh, vol. xiii. p. 131, et seq.; 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