After thirteen years of unmitigated labor, Audubon could have basked in a fame already secure, and could have enjoyed, for a time at least, a leisure handsomely earned. But no sooner had he settled in New York than he entered upon two formidable tasks: one of these was the complete revision of his _Birds of America_, to be issued with its text in "miniature," as its reduced form was sometimes described; the other, which he did not live to see brought to completion, was an elaborate work on the _Quadrupeds of North America_, eventually carried forward in collaboration with the Reverend John Bachman. In his confident and characteristic manner, Audubon at once issued a "Prospectus" of both these undertakings. The more cautious Bachman, in writing on September 13, 1839, to congratulate him upon their safe return, "in spite of storms, calms, and hurricane," said: I am glad that you are about to do something with regard to the "_Small Edition of Birds_." But are you not too fast in issuing your prospectus of _The Birds and Quadrupeds_, without having numbers of both works, by which the public can judge of their merits? My idea, in regard to the latter, is that you should carefully get up, in your best style, a volume about the size of "Holbrook's Reptiles." This would enable you to decide on the terms of the book, I think that two thousand subscribers at $1.00 for each number, might be obtained. But it must be no half-way affair. The animals have never been carefully described, and you will find difficulties at every step. Books cannot aid you much. Long journeys will have to be undertaken. Several species remain to be added and their habits ascertained. The drawings you can easily make, if you can procure the specimens. I wish I had you here, if only for two days. I think that I have studied the subject more than you have. You will be bothered with the Wolves and the Foxes, to begin with. I have two new species of Bats and Shrews to add. The Western Deer are no joke, and the ever varying Squirrels seem sent by Satan himself, to puzzle the Naturalists. It is evident from this letter that Audubon was then intending to proceed with the work on the _Quadrupeds_ alone and that Bachman's active coöperation was secured later. On September 15, shortly after his return to America, he wrote to Thomas M. Brewer on this subject as follows:[173] Now that I am about to commence the publication of the _Quadrupeds of North America_, I will expect your assistance in the procuring for me of all such subjects as may easily be obtained around you. John Bachman is about to give the whole of his collections and his notes to me; and as I intend to open a pretty general correspondence in different parts of the Union, I trust to be enabled to proceed roundly on this fresh undertaking.