Again, both forest and fruit trees, when planted by the hand of man, thrive well in the prairie, if only fire be kept from them. And wherever in the prairie, as on the rocky faces of bluffs, or the banks of streams, fire cannot reach, on account of the absence of sufficient grass and undergrowth to convey it, trees—as pines, oaks, willows, and poplars—abound. The great accumulations of black vegetable mould are to be accounted for in the same way; they are formed out of the burnt and half-burnt vegetable matter left by the annual fires of no one can tell how long a period. In the valley of the Platte, this vegetable mould appears to have been carried away by the stream, which has ever been shifting its channel from side to side, between the bluffs which bound the valley—in so doing floating off the lighter portions of the soil, and leaving sand and gravel only in its deserted beds. On the dry prairie between Omaha and the mountains I saw, for the first time, some of the _feræ naturæ_ of America in abundance. Hitherto I had frequently observed that there was almost a total absence of animal life from the roadside. I could count up the rare occasions on which I had seen either bird or beast. I had twice seen colonies of a social crow resembling our rook. In Georgia I had seen two birds, one about the size of a thrush, and the other rather smaller than a sparrow. In Alabama I had seen some wild deer and wild ducks. In a journey of several thousand miles I had seen no other wild four-footed or feathered creature. I had attributed the deficiency of the latter partly to the severity of American winters, which had taught them migratory habits, and partly to the sparseness of the population in the Southern States; for though it is true that the presence of civilised man is incompatible with the existence of some species, yet there are other species to which man, by his cultivation of the ground, and as it were by the crumbs that fall from his table, becomes the chief purveyor, and whose numbers therefore increase almost in proportion to the degree in which a country becomes settled. But here, on this arid plain, and in mid-winter, neither naturalist nor sportsman could have had anything to complain of. Animal life was in abundance. In the course of one day I saw from the windows of the car three herds of antelopes (in one of which I counted thirty-eight), two wolves, prairie-fowl in great numbers, plenty of a species of bird resembling our English lark, several hawks, and innumerable colonies of prairie-dogs. As their villages are frequently at a distance from water, these agile and amusing little animals are supposed to be capable of living without drinking. I saw nothing of the owls and rattlesnakes who have been admitted by the prairie-dogs to a joint tenancy of their subterranean homes. Doubtless, if one were to examine on foot the banks of the river, and the rocky bluffs that bound the valley, my small list might easily be made a large one.