"It has always appeared to us unaccountable that birds of prey, as vultures, could scent carcasses at such immense distances, as they are said to do. We were led to call in question the accuracy of this opinion, on recollecting the observations of some travelers, who have remarked birds of prey directing their course towards dead animals floating in the rivers in India, where the wind blows steadily from one point of the compass for months in succession. It was not easy to conceive that the effluvium from a putrid carcass in the water, could proceed in direct opposition to the current of air, and affect the olfactory nerves of birds at so many miles distant. We were disposed to believe that these birds were directed towards the carrion rather by the sense of seeing than by that of smelling. This opinion is confirmed by the following observations of our friend Audubon, communicated to us by him some time ago for our _Philosophical Journal_." Here follows at length Audubon's communication, from which I extract the following passages: "My _First Experiment_ was as follows: I procured a skin of our common deer, entire to the hoofs, and stuffed it carefully with dried grass until filled rather above the natural size,--suffered the whole to become perfectly dry and as hard as leather--took it to the middle of a large open field, and laid it down upon its back with the legs up and apart, as if the animal were dead and putrid. I then retired about a few hundred yards, and in the lapse of some minutes a vulture coursing around the field, tolerably high, espied the skin, sailed directly towards it, and alighted within a few yards of it. I ran immediately, covered by a large tree, until within about forty yards, and from that place could spy the bird with ease. He approached the skin, looked at it without apparent suspicion, raised his tail and voided itself freely (as you well know all birds of prey in a wild state generally do before feeding), then approaching the eyes, that were here solid globes of hard, dried, and painted clay, attacked first one and then the other, with, however, no farther advantage than that of disarranging them. This part was abandoned; the bird walked to the other extremity of the pretended animal, and there, with much exertion, tore the stitches apart, until much fodder and hay were pulled out; but no flesh could the bird find or smell; he was intent on finding some where none existed, and, after reiterated efforts, all useless, he took flight, coursed round the field, when, suddenly turning and falling, I saw him kill a small garter snake and swallow it in an instant. The vulture rose again, sailed about, and passed several times quite low over the stuffed deer-skin, as if loth to abandon so good-looking a prey.