THE 



LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES,] 



FEBRUARY 1840. 



XIII. An Account of some Experiments made m the South of 

 Virginia^ on the Light of the Sun. By John Wm. Draper, 

 M.D., Professor of Chemistry in the University of Nex<o 

 York. 



To the Editors of the Philosophical Magazine a7id 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 Morichini's 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. 16. No. 101. Feb, 1840, G 



