They are furnished with astonishing capabilities for performing these very long journeys. You are acquainted with their slender forms, so exactly adapted for cutting through the air, and their long, beautiful wings. Each of these wings is moved by a muscle of prodigious power, situated on each side of the breast-bone. Possibly you may have noticed in larks and other birds, that are in the habit of flying long distances, which are eaten, what a large proportion of their flesh is in these two muscles; in the swallow, it greatly exceeds the weight of the flesh of all the other parts of the body. You will hardly believe it when I tell you, that the swift is able to fly at the rate of more than a hundred miles in an hour. The little bird that perched upon your chimney this morning, may perch to-morrow night upon one of the pyramids of Egypt, and next week may be at the Cape of Good Hope. You think a great deal of travelling twenty miles an hour on a railway, but you see that is slow compared with the travelling of the swallows. Instead of thus following the summer about over the surface of the earth, some creatures, that love warmth, make the best of it where they are. Some birds get into holes and other sheltered places, put their heads under their wings, and so sleep away the winter months. The pretty little black-eyed dormouse makes up a snug nest, and does the same, and so do some other of our common animals. During this inactive period, all the functions which are necessary to support life become fitted to a state of repose; the circulation gets slower, and the supply of inward heat sinks to the lowest temperature which life will bear. I dare say you have often found some sorts of snail-shells with the snail inside, and the mouth sealed up firmly, and have taken them for dead: this is not the case. The covering is only put over for the winter to keep out the cold, and the creature lives till spring without food or motion. How it must enjoy the first bright days of spring, when it opens its eyes after its long nap, reaching out its horns, and dragging its shell over the green grass. [Illustration]