"The plumage of the wings grows out from the skin, just as feathers grow from any other part of the body, only the large ones are fastened to the bones, so that they stay tight in their proper places.

If they were loose, they would fly up when the bird beats the air with its wings, and get out of order.

See how smoothly they lie one over another! When the bird closes its wings, they come together snugly along its sides.

But when the wing is spread, they slide apart--yet not too far to form a broad, flat surface, quite stiff, but light and elastic.

By beating the air with the wings birds fly along.