130 Notice of Auduhori's Birds of America. 



would probably be rendered more perfect by using fine hair, or 

 wool, or better still a single thread of the silk worm, instead of a 

 platinum wire. As difraction takes place at the edges of trans- 

 parent as well as opaque bodies, probably an apparatus of the 

 kind above described, made of very fine spun glass, would exceed 

 all others in delicacy and power, as refraction in this would co- 

 operate with difraction. Since writing the above, Prof. Sturte- 

 vant has suggested the mode of fastening parallel fibres into a 

 wooden frame by gluing pieces of wood upon its exterior sides. 

 I have acted upon this suggestion and constructed an instrument 

 with fine silk thread, which, though immensely inferior to the 

 vane of the feather, produces phenomena similar in kind. 



As my frontier location deprives me of the means of attaining 

 the desirable perfection in the constructions which I have de- 

 scribed, it is hoped that others more favorably situated, will be 

 able to realize what I have hinted at above. It remains to be 

 determined, whether art, in the construction of a difracting in- 

 strument, will ever attain to that perfection which is presented to 

 us by the hand of nature in the vane of the feather. Even with 

 the latter we are able to render the chromatic effects of difraction 

 and interference as conspicuous to a class of students as those of 

 refraction. Prof. Sturtevant lectured a few days ago upon the 

 phenomena of the feather for the first time, to the great satisfac- 

 tion of his audience. 



During the progress of the above investigations, several inqui- 

 ries have arisen, which Prof. Sturtevant and myself are now 

 pursuing, and one or both of us may be expected to be heard 

 from again upon this subject. 



Illinois College, April 16, 1841. 



Art. XV. — The Birds of America, from drawings made in the 

 United States and their Territories ; by John James Audttbon, 

 F. R. SS. J^ond. and Ed., &c. &c. Vol. 11. New York, pub- 

 lished by J. J. Audubon : Philadelphia, J. B. Chevalier. 



The extended notice we gave a year since of the general de- 

 sign of this work, and our full account of the author, his personal 

 history, the surpassing merits of his former work, and the promise 

 of equal excellence given to the pubhc by the first volume of the 



