Humming Birds

The huniniing bird.s aro perbaps the uiot reinarkable cxamples in the world of' the machinery of flight. The power of poUing thciuselves ia the air, remaining absolutely stationary whilst they scarch the blossoms f'or insects, is a power ossential to theirlife. It is a power, aecordingly, which is emoyed by them in the highest perfectioD. When they need progressive flight it is effected with Kuch velocity as to elude the eye. The action of' the wing in all these cases is far too rapid to onable the observer to detect the exact diffcrence betwecn the kind of niotiqn which keeps the bird at absolute rest in the air, and that which carries it along with suou immense velocity. But there can be no doubt that the chango is one froru a short, quick stroke, delivered obliquely ibrward, to a í'ull stroke, more bIow, 1m1 defiverea perpeödionhny.