Some of the swimming birds in their flight are feeble and slow; others are incapable of even rising from the water, being only furnished with rudimentary wings. Again, there are species which possess extraordinary powers of traversing the air, their well-developed wings enabling them to pass through space with wonderful rapidity. The Albatross is met with on the high seas at a vast distance from the shore. Others, as the Petrels, seem to revel in storms and tempests, mingling their wild cry with that of the storm-tossed waves. The sailors, who look anxiously to windward at the dark horizon, where the clouds are surcharged with torrents of rain ready to burst on the ship, are assured of the approaching tempest by the circling flight of the white-winged Albatross, as it is seen through the obscure and threatening mist. The whole order of Natatores swim and dive without saturation, their plumage being anointed by an oily liquid furnished by certain glands in their skin, which renders them impervious to moisture. This immunity from the effect of water is further assisted by the disposition and structure of their feathers, which, being smooth and three-cornered, with the barbules closely interlaced, cause the water to glide off their polished surface; while the down beneath the feathers of which we have spoken protects their bodies from the cold, maintaining their natural heat, and enabling them to resist the cold of the most rigorous winter. The Natatores are numerous both in species and individuals, having their habitat in all countries. According to Prince Charles Bonaparte, one of the most eminent of European naturalists, those which frequent the sea-shore alone constitute one-fourteenth part of all the birds on the globe, and the number of species he reckons at nine thousand four hundred. They feed on vegetables, insects, mollusks, and fishes. They seek the coast in the breeding season, where they build their nests on the sand, or in nooks and crannies of the rocks, or on the margin of lakes and rivers.