Mr. Atkinson on Sir G. S. Mackenzie’s Remarks. 187 
distinctly what my meaning was, and there leave the ques- 
tion. 
The result which I obtained in 1825, and which M. Mel- 
loni has so fully verified, was this: The effect from a lumin- 
ous hot body, without any screen, upon a black and a white 
surface respectively, was observed to be in a certain ratio; 
the same effects when a transparent screen was interposed 
were in a different and greater ratio. M. Melloni’s theory is, 
that this new and different relation to suzfaces is communi- 
cated to the rays by, and in, the act of passing through the 
screen; so at least I understand it. Now ¢his is what I objected 
to as a very singular theory, discordant (as I conceive) with 
allanalogy, and needless, in as much as the effect is explained 
by the much simpler supposition, that there are two distinct 
sorts of heat emanating at the same time from the luminous 
body, distinct in their relations to surfaces as well as to screens. 
It was to this single point alone that my remarks applied. 
With the other valuable results of M. Melloni I am not now 
concerned. I will merely add, in the present unformed state 
of this entire branch of our knowledge it seems hardly sate 
to adopt any theory, except as a mere conjectural guide. 
But I have the greatest hopes that before long we shall be in 
a condition to advance to some satisfactory general principles, 
when I find such an instrument as M. Melloni’s in active 
employment in the hands of such able and zealous experi- 
menters as are now engaged with it in Edinburgh and 
Dublin. 
XXXV. On Sir G.S. Mackenzie’s Remarks on certain Points 
in Meteorology, &c., inserted in Lond. and Edinb. Phil. Mag. 
for November 1835. By Josepu Arxinson, Esq., Secretary 
to the Carlisle Literary and Philosophical Society. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
HAVE been induced by Sir G. S. Mackenzie’s remarks 
on the equinoctial gales, contained in your Magazine for 
November last, to look for a corroboration of his supposition 
that the equinoctial gales have of late come from the eastward, 
but I cannot find that such has been the case here. ‘The si- 
tuation of Coul is most probably the cause of the easterly 
winds being so prevalent there. On the 22nd of September, 
which is the day mentioned as the one on which he wrote his 
letter, while an easterly wind was blowing, I find a southerly 
wind noted in my journal. ‘This of itself is enough to show 
X 2 
