ALTHOUGH not by a balloon, yet the Atlantic has been crossed in the air, and "what has been can be." There are enough well-authenticated cases of the occurrence of American wild birds on the west coast of Europe to prove that the trip can be made by birds, and it is probable that successful navigation of the air will be the fruit of careful study of that natural flying-machine, a bird's wing.
Every person who has not given more than a passing thought to the mechanism of flight is confident that he understands the whole subject, and tells you, if you ask, that the bird rows through the air with its wings, and that our lack of available force and of a sufficiently strong and light material is the only difficulty in the way of a successful flying-machine.
A very little study of a bird's wing and its action will show that it is not by any means simple, and that every part and every curve and angle has a use, and helps in the performance of the function of the whole, which function is not yet perfectly understood, but does not in the least resemble the action of a paddle or oar. We shall also learn that all attempts to construct flying-machines have been made with an utter disregard of every thing that a wing might have taught. To this sweeping assertion I know of only two exceptions; a boy's kite, and the little circle of cardboard which runs up the kite-string in such a mysterious way, bear a very slight resemblance to a wing, in their mode of action, and may contain the germ of a successful flying- machine.
To point out some of the facts already known about flying is one of the objects of this paper; another is to show how much there is to be learned about any natural object, and the way to set about it; for he who knows all that is to be learned about a wing has a good store of useful information, but he who knows all that may be learned from a wing is a wise man.
Let us examine a feather. When I say "examine a feather," I mean, let "every one take the trouble to pull a quill-feather from an old duster, or find an old quill-pen, or in some way get possession of an actual feather, to see for himself what I wish to show; for, if what I have to say is not worth this trouble, it is not worth reading at all.
Having found your feather, notice, first, the great strength of the shaft, compared with its lightness, and how secured by placing almost all the material on the outer wall of the quill. Notice, too, that the quill, where strength is most necessary, is tubular, while the rest of the shaft has a groove on its lower surface, and tapers toward the tip,