Thus began a correspondence between the youth of fifteen and the veteran of fifty-five, which led to an intimate friendship that lasted during Audubon's active career, and was an undoubted stimulus to young Baird, whose talents, enthusiasm and industry were quickly appreciated by the older naturalist. Baird answered Audubon's letter on June 20, and proffered his services in collecting mammals, saying that while they were more difficult to find than birds, he hoped "by increased exertion to make up the difference"; he also added: "I have seen some numbers of your work now publishing, and admire them very much. I have no doubt that it will do more to spread a love of Natural history, than any work ever published. For my part I read the description of birds and the episodes in your _Ornithological Biography_ with the same motive of pleasure as I used to read a favorite novel." In Audubon's immediate reply of the 22nd, he said: It is impossible at present for me to give you any precise idea of the work on our quadrupeds which I have in contemplation to publish, any further than to say to you, that it is my intention, as well as that of my friend, the Revd John Bachman, of Charleston, S. C., assisted by several others of our best naturalists, to issue a work on the Mammalia of North America worthy of the naturalist's attention, both at home and abroad.—Through our joint efforts, and assisted as we hope and trust to be, by numerous friends and acquaintances in different portions of our Wide Union, we expect to collect, not only new species, but much of valuable matter connected with their geographical range, and particular habits. For instance, in your assistance in this department as well as in ornithology, you may be able to send us valuable intelligence respecting the Shrews, Mice, Rats, Squirrels, etc., found in your immediate vicinity &c.—and by saving and forwarding specimens to us, be able also, in all probability, to place into our hands, objects never before known to the World of Science. Whatever information we thus receive is sacredly published under the name of the friend from whom we receive the information, etc. I have sent you the Zoological report of Docr. De Kay. His _Corvus cocolotle_ [cacolotl] is really our Raven. _Supposed_ by some inexperienced European naturalists to be distinct from the Raven of Europe, which, however, is a gross error.[179]... The thrush which you have described, and which you kindly offer to send me, may be new, but perhaps you are not acquainted with the Turdus Nanus of my work, to which it appears, if not the same, probably a new variety! _Nous verrons_....