Observations and Experiments on Light. 123 



Art. XIV. — Observations and Experiments on Light ; by Sam- 

 uel Adams, M. D., Professor of Chemistry and Natural History 

 in Illinois College, Jacksonville, III* 



Sometime in July, 1838, while on a mineralogical excursion, I 

 accidentally noticed the wing-feather of a bird lying upon the 

 ground ; and being struck with the delicacy of its tints, I took it 

 up to examine it. Observing that the vane of the feather ap- 

 peared very thin and nearly transparent, I held it between my 

 eye and the sky, which was very clear with the exception of a 

 few fleecy clouds, that contrasted finely with its rich blue. I 

 was very much interested to observe, that the clouds and all light 

 colored objects, which were highly illuminated, were seen through 

 the vane of the feather beautifully fringed with the colors of the 

 rainbow. I supposed that this phenomenon depended upon the 

 peculiar structure of the vane of the feather, and intended to in- 

 vestigate it as soon as I could find leisure. I did not, however, 

 resume the subject till accident again called my attention to it. 



About the 20th of June, 1839, while walking in the College 

 grove, I happened to observe lying upon the ground some wing- 

 feathers of the Jay, which reminded me of my former experiment. 

 I collected the feathers, and after observing the same phenomena 

 that I had noticed on the former occasion, I held the vane of the 

 feather between my eye and the sun, and was greatly surprised 

 at the gorgeous display of colored spectra that were seen through 

 it, arranged in the most exact mathematical order. The sun was 

 seen in its natural position, slightly tinged with red, with its 



* To the Editors of the American Journal of Science and Arts. 



Messrs. Editors — When " Observations and Experiments on Light" were for- 

 warded to you for publication in the Journal of Science, I was not aware that 

 Fraunhofer had anticipated the leading investigations of that communication. 

 Pressing engagements, and frequent attacks of intermittent fever, prevented me 

 from making so full an examination of the works of others on the subject as was 

 desirable. I have since ascertained, that Fraunhofer has anticipated the leading 

 results of my observations, in a series of experiments made by him by passing a 

 beam of light through gratings, and examining the spectra produced through a 

 telescope. (Herschel on Light, § 740, et seq.) I do not find, however, that the 

 effect of the feather upon light has been before noticed, or that Fraunhofer ever 

 exhibited the spectra upon a screen. You will oblige me by appending this as a 

 note to my communication.' Yours, &c. Samuel Adams, 



Rlinois College, May 21, 1841. 



