130 Notice of Audubon’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 deseribed, made of very fine spun glass, would exceed 
atl 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 sitk 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 thefeather. 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 afew days ago upon the 
phenomena of the feather for the first time, to the great satisfae- 
tion of his audience. 
During the progress of the above investigations, several ing 
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 oe 
Illinois College, April 16, 1841. 
Art. XV.—The Birds of America, from drawings made in the 
United States and their Territories ; by Joun James AuDUBON, 
F.R.SS. Lond. and Ed., &c. &c. Vol. If. New York, pub- 
lished by J. J. Audubon: Philadelphia, J. B. Chevalier. . 
Tur extended notice we gave a year since of the general de- 
sign of this work, and our full account of the author, his pe 
history, the surpassing merits of his former work, and the promise 
of equal excellence given to the public by the first volume of the 
ae 
