“Vultures and the marabou stork fly at enormous altitudes. I believe that every species keeps to its own particular elevation, and that the atmosphere contains regular strata of birds of prey, who, invisible to the human eye at that enormous height, are constantly resting upon their wide-spread wings, and, soaring in circles, watching with telescopic sight the world beneath. At that great elevation they are in an exceedingly cool temperature, therefore they require no water; but some birds that make long flights over arid deserts, such as the marabou stork and the bustard, are provided with water-sacs; the former in an external bag a little below the throat, the latter in an internal sac, both of which carry a large supply. As the birds of prey that I have enumerated invariably appear at a carcase in their regular succession, I can only suggest that they travel from different distances or altitudes. Thus, the marabou stork would be farthest from the earth; the large bare-necked vulture would be the next below him, followed by the red-faced vulture, the buzzard, and the crow that is generally about the surface. From their immense elevation, the birds of prey possess an extraordinary field of vision; and, although they are invisible from the earth, there can be no doubt that they are perpetually hunting in circles within sight of each other. Thus, should one bird discover some object upon the surface of the earth below, his sudden pounce would be at once observed and imitated by every vulture in succession. Should one vulture nearest the earth perceive a body, or even should he notice the buzzards collecting at a given point, he would at once become aware of a prey; his rush towards the spot would act like a telegraphic signal to others, that would be rapidly communicated to every vulture at successive airy stations.