only a proof that he is keeping his balance. The kestrel is not the only bird that hovers. The sparrowhawk can. So can all the finches, more or less, when taking seeds from a plant which will not bear their weight or which they cannot otherwise get at; also when taking insects on the wing. Sparrows do the same. Larks hover in their mating season uttering a short song, not the same as when they soar. Numerous insects can hover: the great dragon-fly will stop dead short in his rapid flight, and stay suspended till it suits him to advance. None of these require any current or wind. I do not think that hovering requires so much strength of wing or such an exercise of force as when birds rise almost straight up. Snipes do it, and woodcocks; so also pheasants, rocketing with tremendous effort; so also a sparrow in a confined court, rising almost straight to the slates. Evidently this needs great power. Hovering is very interesting; but not nearly so mysterious as at least one other power possessed by birds. BIRDS CLIMBING THE AIR Two hawks come over the trees, and, approaching each other, rise higher into the air. They wheel about for a little without any apparent design, still rising, when one ceases to beat the air with his wings, stretches them to their full length, and seems to lean aside. His impetus carries him forward and upward, at the same time in a circle, something like a skater on one foot. Revolving round a centre, he rises in a spiral, perhaps a hundred yards across; screwing upwards, and at each turn ascending half the diameter of the spiral. When he begins this it appears perfectly natural, and nothing more than would necessarily result if the wings were held outstretched and one edge of the plane slightly elevated. The impulse of previous flight, the beat of strong pinions, and the swing and rush of the bird evidently suffice for two or three, possibly for four or five, winding movements, after which the retarding effects of friction and gravitation ought, according to theory, to gradually bring the bird to a stop. But up goes the hawk, round and round like a woodpecker climbing a tree; only the hawk has nothing tangible into which to stick his claws and to rest his tail against. Those winding circles must surely cease; his own weight alone must stop him, and those wide wings outstretched must check his course. Instead of which the hawk rises as easily as at first, and without the slightest effort--no beat of wing or flutter, without even a slip or jerk, easily round and round. His companion does the same; often, perhaps always, revolving the opposite way, so as to face the first. It is a fascinating motion to watch.