INTRODUCTION. UMEROUS and diversified as are the animals of the Class MAMMALIA, to which the two preceding Volumes of "CASSELL'S POPULAR NATURAL HISTORY" were devoted, it is remarkable that the bat alone is endowed with the power of flight; a flight which is strong, rapid, and marked by sudden evolutions and turns, executed with astonishing celerity. In the next Class, AVES, which demands our consideration, the body is invariably covered with feathers, and the anterior extremities are organs of flight alone. As the plumage, in its endless modifications, is intimately connected with the habits of the species, these variations are studied by Naturalists, not only as demonstrative of consummate design on the part of the Great Creator, but as an index to the manners of birds, and as a clue to a natural arrangement. The entire mechanism of the body, indeed, corresponds precisely with the organs of flight. Long and slender, like a snake's, the central point of gravity would have been wanting for maintaining an even, steady course; while, had it been round, there could have been no cleaving of the sky, like that of an arrow in its course. But the body is beautifully boat-shaped; the prow being formed of the small head and pointed beak, and the rudder by the broad, expanded tail; so that the resistance of the air may be effectually overcome. If, too, the plumage and the skin be removed, how fine, how large, how powerful will the muscles appear, expressly destined for the motion of the wings, constituting, as they do, the solid mass of the whole chest, and being more in volume than all the others put together. The destined tenants of the upper air, birds, borne on rapid wings, transport themselves from place to place, and even from one country to another, with ease and safety. Familiar with the tempest, they rise till lost amidst the clouds; and, from their lofty pinnacle, look down on the outspread earth, with its seas and rivers interspersed on its surface. Yet are they not restricted to the regions of the air; the land and the waters are theirs also; some traversing the fields, some trooping around the dwellings of man, some wading the treacherous morass, some scouring the sandy desert, some living in the umbrageous shade of the sequestered thicket or the lonely forest, and some diving and sporting on the ocean billows. The appearance of birds is a special attraction to every intelligent observer. As Thomson says: "The redbreast pays to trusted man His annual visit. Half afraid, he first On the warm hearth; then, hopping o'er the floor Eyes all the smiling family askance, And pecks, and starts, and wonders where he is; Till more familiar grown, the table crumbs |