New York, July 29, 1841.
My dear Sir,—
I have not had time to answer your interesting favor of the 21st until this morning, being now constantly engaged in the figuring, &c., of the Quadrupeds of Our Country; by which I mean that I actually work from daylight every day until I retire to my necessary repose at night.
Your observations upon the birds of passage the last spring are what they have been almost throughout the U. S. The very backward spring which we have experienced this year did no doubt retard the coming into the States the millions of passenger birds that come to us from beyond our limits. The Fly-catcher of which you are in doubt is nevertheless the M. Pusilla, and you must not be surprised to find perhaps some discrepancy between the specimens you have procured and the descriptions you may have read, as among mine these differences are quite obvious and belonging to either sex or age, as is indeed the case with most of our birds as well as among many of our quadrupeds....
I cannot at present tell you when I may have the pleasure of meeting you at your own domicile, and yet this may happen quite unexpectedly.
Do you pay attention to the quadrupeds around you? If not, I wish you would!—and moreover I should be highly pleased to hear of your procuring for us all such as may be found in your vicinity. You have Bats, Wood Rats, & Mice, Weasels, &c., &c., all of which I should like to possess specimens at your hands. Could you not save all that you come across with in this way, place them in common good Rum, and forward them to me at once or as soon as you have some 2 or three species. I will most cheerfully pay all expenses to Philadelphia addressed to J. B. Chevalier, No. 70 Dock Street.
I am now as anxious about the publication of the Quadrupeds as I ever was in the procuring of our Birds, indeed my present interest in Zoology is altogether bent toward the Completion of this department of Natural Science.
Do please write to me often as I am always glad to hear from you, and when I am somewhat slow in answering your letters, be assured that it is altogether on a/c of the excess of Labour that I have to go through.
Believe me with sincere good wishes
Your friend and servant,
John J. Audubon.