Mr. R, Hunt on the Changes of Bodies in Darkness. 271 
rays, and still more strongly convinced by the recent re- 
searches of Sir John Herschel of the existence of solar rays 
broadly distinguished from Heat and Lieut, I do not think 
we have as yet a sufficient amount of experimental evidence 
to warrant ‘us in receiving that broad distinction as truth, 
which would refer all chemical changes effected by solar radia- 
tion to a new element. I should not venture to trouble you 
with any remarks on this subject, but that I fear the adoption 
of the ideas and the proposed nomenclature of Dr. Draper 
will involve a very complex inquiry in inextricable difficulty. 
My only desire is the discovery of the truth; and believing, 
as I do at present, that Dr. Draper has given a wrong in- 
terpretation to his very excellent experimental results, I hope 
he will do me the justice of considering that I am actuated 
by the purest principles in opposing his views; and I do as- 
sure you that I shall feel much pleasure in receiving from 
him, or any other inquirer, any correction, if I have drawn 
wrong conclusions from the results of my experiments. 
There are several points in the communications referred 
to, to which I cannot give my assent, particularly to ‘the en- 
tire independence throughout the spectrum of the luminous 
rays that give to the organs of vision the impression of colour 
and the tithonic rays,” but Iam not prepared fo prove the 
contrary. Again, “as to the independence of these rays and 
the rays of heat,” I find myself in the same situation, although 
it appears to me that I have a stronger fact connected with 
the influence of the moonbeams than the proof brought for- 
ward by Dr. Draper, “ that strong impressions of the moon's 
surface may be taken on sensitive plates.” I will describe 
my experiments. Copper-plate engravings and woodcuts 
were placed on well-polished plates of copper, and exposed 
in photographic copying frames, well-guarded by flannel 
cushions and glass from the deposition of moisture, for one 
and two hours to bright moonlight. In each case most per- 
fect copies of the prints were made on the copper, which were 
evident before the application of vapour, and became beauti- 
fully defined when the plates were breathed upon, but were 
not improved by the vapours of mercury or iodine. The un- 
favourable state of the weather alone has, for the present, put 
a stop to further inquiries. It is difficult to deal with this 
question in the present stage of our researches. I am in- 
clined to regard the pheenomena which I have above described, 
and the fact mentioned by Dr. Draper, of the moon impress- 
ing her own image on Daguerreotype plates, as belonging to 
the same class, and to be attributed, neither to the influence 
of “calorific rays,” which cannot be detected in the moon- 
beams, nor to ‘ chemical rays,” although the light of the full 
