Prof. Powell’s Remarks on M. Melloni’s Paper. 23 
Hoping for an immediate insertion of this, I shall reserve 
any remarks on the probable errors in the experiments, and 
their causes, for a future occasion. 
I am, Gentlemen, yours, &c. 
24, Stephen’s Green, Dublin, H. Hupson. 
Nov. 11, 1835. 
VII. Remarks on a Paper on the Transmission of Calorific 
Rays, &c. by M. MEtont, in the Phil. Mag. and Journal 
of Science, No. 42. By the Rev. B. Power, M.A., F.R.S., 
Savilian Professor of Geometry, Oxford.* 
N the last Number of this Journal (vol. vii. p. 475) a short 
communication appears from M. Melloni, in which that di- 
stinguished experimenter has honoured me with a reference to 
the experiment which I tried in 1825, which forms the basis of 
a peculiar view of the nature of the heat originating from lu- 
minous hot bodies, and which M. Melloni has since successfully 
verified with his extremely delicate apparatus, so as entirely to 
remove all doubt, which (I presume from the silence of phy- 
sical writers) must previously have been felt on the subject. 
But while he speaks with approbation of that experiment, 
M. Melloni refers to my views connected with it in terms which 
imply a most singular misconception of them, and on which 
I therefore feel it necessary to offer a very few remarks. 
M. Melloni describes me as “ endeavouring to explain his 
results by hypotheses” which are untenable. Now, I am not 
aware of having attempted to explain M. Melloni’s results at 
all. All that I have contended for is, that if the distinction 
between two kinds of heat, “luminous and obscure” (as the 
author terms them), be admitted, (and he himself, I believe, 
admits it,) it will follow, that all results which have hitherto 
been commonly stated as referring to “ radiant heat,” will 
require now to be more precisely worded, and we must say 
which sort of radiant heat we mean, in all cases where there 
may be both present. 
That particular result which M. Melloni obtained in the 
repetition of my experiment with the thermomultiplier, and 
which so strongly confirms it, I have, indeed, adverted to as, 
to my apprehension, ill explained by the gratuitous hypothesis, 
that the heat acquires a new property with regard to its re- 
lations to surfaces by merely passing through glass; which 
seems to me at once needless and contrary to all analogy; 
* Communicated by the Author. 
