Page:Popular Science Monthly Volume 8.djvu/469

Rh  the imposture at once, and attacked the young ferret so savagely that she broke two of its legs before I could remove it. To have made this experiment parallel with the other, however, the two mothers ought to have littered on the same day. In this case the result would probably have been different; for I have heard that under such circumstances even such an intelligent animal as a bitch may be deceived into rearing a cat, and vice versa.—Nature.



UMEROUS attempts have been made at different times to construct a machine capable of propelling itself through the air. All kinds of aërial propellers have in turn been tried; such as screws, beating wings, umbrellas which open and shut during their reciprocating motion, inclined planes, aërial wheels. But though many of these projects called forth considerable inventive ability, yet, until quite recently, the helicopteron (from έλικός any thing spiral or twisted, and πτερόν, a wing—that is, a machine furnished with an aerial screw-propeller) was the only type of machine which had succeeded in raising itself in flight. Several of these helicopterons have been constructed since 1784, at which date Bienvenu made the first that flew. The best known and the most perfect was that which Ponton d'Amécourt constructed in 1864, and which raised itself for a moment by a sudden motion to a height of two and a half metres. It was formed of two superposed right and left handed screws, put in motion by a watch-spring. All other methods of artificial flight, including those of propellers with wings beating the air like those of a bird, remained ineffective, and were the subjects of conflicting hypotheses as to the nature of flight.

In beginning our studies, we have thought that the best means of getting rid of the multiplicity of hypotheses and of conflicting opinions would be to divide the flying-machines that have been invented into a small number of general types; then to reduce each of these types to its essential elements, and finally to design a flying-machine of each of these simplified types possessing all the really essential parts, and easy to construct.

Leaving out of consideration the inventions which are evidently defective, we have thought it possible to divide the majority 