Describing a night of extreme coldness, the poet says: "The owl, for all her feathers, is a-cold." That warm covering of the bird must be portable as well as warm; it weighs about an ounce and a half. But the covering of birds would be useless to them if the showers to which they must be exposed were absorbed by the plumage, so that it became a heavy clinging mass. An oily secretion makes it waterproof; we have all seen the duck free itself by one shake from every trace of its recent bath. The heavy skeleton that befits pedestrian creatures, would disable the bird from flight; so it is provided with tubes of thin bone, surrounding a cavity filled with air. Its pinions must be light as well as strong; observe how the light barbs of the feather have roughened edges so that they form one strong continuous surface, almost impervious to the air which they strike. The air in the bones of birds and in other cavities of the body, heated too by an inner warmth much greater than that of man, contributes something to their buoyancy. Their speed and endurance are enormous. It is said that the swallow's flight is ninety miles an hour. One long stretch across the North Sea brings the sea-fowl from Norway to Flamborough Head; they rest for a short time after this flight, and pass inland, not the worse for their exploit. You may infer from the beak of a bird its habits and its food. The bill of a woodpecker is a pointed tool, tipped with hardest horn, to break open the bark of the tree for insects. The flat bill of the duck has plates of horn at the side; an excellent instrument for straining off the water and retaining the food. The bill of the snipe is long, and narrow, and sensitive, to pierce the marshy ground, and feel after its food. We might go on for hours multiplying such instances, and from every part of the field of creation.