When a bat goes to sleep it always hangs itself up by the claws of its hind feet. In an old church tower, or a stable loft, you may often find bats suspended in this singular way. And there is a reason for it. The bat wants to be able, at the first sign of danger, to fly away. Now if it lay flat upon the ground to sleep, as most animals do, it would not be able to fly quickly; for it would have to clamber up a wall or a post to some little height before it could spread its wings. And this would take time. But if it should be alarmed while it is hanging by its hind feet, all that it has to do is to drop into the air and fly off at once. BATS IN THE DARK There is something else, too, that we must tell you about bats. They have the most wonderful power of flying about on the darkest night, without ever knocking up against the branches of trees, or any other obstacles which they may meet on their way. It used to be thought that this was because they had very keen eyes. But it has been found out that even a blind bat has this power, which seems really to be due to very sensitive nerves in the wings. You can feel a branch by touching it. But a bat is able to feel a branch _without_ touching it, while it is eight or ten inches away, and so has time to swerve to one side without striking against it. THE WINTER SLEEP Bats, like hedgehogs and squirrels, pass through the winter in a kind of deep sleep, which we call hibernation. It is more than ordinary sleep, for they do not require any food for months together, while they scarcely breathe once in twenty-four hours, and their hearts almost cease to beat. If the winter is cold throughout, they do not wake at all until the spring. But two or three hours' warm sunshine arouses them from their slumber. They wake up, feel hungry, go out to look for a little food, and then return to their retreats and pass into the same strange sleep again. AN INTERESTING SPECIMEN