THE 
LONDON AND EDINBURGH 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[THIRD SERIES.] 
FEBR VARY 1840 . 
XI I L An Account of some Experiments made in the South of 
Virginia^ on the Eight of the Sun. By John Wm. Draper, 
M.D., Professor (f Chemistry in the University of Nexv 
York. 
To the Editors of the Philosophical Magazine and Journal. 
Gentlemen, 
T HAVE just seen in the Journals for the current month, 
brought out by the British Queen, a letter from Sir J. 
Herschel to the [British] Association for the Advancement of 
Science, in reference to some remarkable actions of the dif- 
ferent colours of the solar spectrum. 
About five years ago, having the advantage of a bright and 
almost tropical sky, I amused myself with attempting a repe- 
tition of Morichinfs experiment for the magnetizing of steel, 
and was led to some results in respect to the chemical action 
of the sun’s rays, which appear to bear very much on the 
subject of the letter above alluded to. Most of these have 
been published in the Journal of the Franklin Institute of 
Philadelphia ; but as they do not appear to have been noticed 
in England, I will ask the favour of a page or two of your 
excellent Magazine, to give my testimony on a subject, which 
now appears to excite so much interest. 
1. If you pass a beam of the sun’s light through a solution 
of chromate of potassa, it can no longer blacken a piece of 
sensitive paper; if you converge the light which has thus 
passed through a stratum of this fluid, by means of a lens, 
chloride of silver will remain for a long time without much 
change, in the focus. 
The list, which was published in the Journal above named, 
of solutions possessing this power, is as follows : 
Phil Mag. S. 3. Vol. No, 101. Feb. 1840. G 
