Page:Popular Science Monthly Volume 8.djvu/475

Rh tail, and which can be inclined upward, or downward, or to one side, and be loaded with wax so that the centre of gravity of the machine can be brought to the proper position.

The warping of the wings, O L, is obtained by the mobility of the wing and of the little fingers, M N, supporting them on the large rods, O M L, which do not partake of this rotation, A little ligament of caoutchouc, D B, connects the posterior interior angles of the wings with the middle of the central rod of the machine. This ligament, whose function is similar to that of the posterior paws of the bat, plays the part of an elastic sheet to our wing, so closely resembling the topsail of a schooner. The torsions of the wing are thus automatically regulated, as required, by the combined action of the pressure of the air and of this elastic ligament. The interior third of the surface of the wing acts like a kite during the elevation as well as during the depression of the wing. The external two-thirds, corresponding to the primary and secondary quills of birds, propel and sustain the machine during the downward motions of its wings. The little drawing in the corner shows the wings just about to begin their downward beat. During the elevation of the wing the terminal feathers conform to the sinusoidal track along which they progress in the air; it thus only cuts the atmosphere without acting against it. To start the machine, we simply abandon it to itself in the air.

This machine was exhibited before the Society of Aërial Navigation on the 2d of June, 1872, and flew several times more than seven metres—the length of the public hall raising itself in a continuous manner, with an accelerated velocity, along a line of flight inclined 15° to 20°. In an open space, the artificial bird flew over twelve to fifteen metres, elevating itself during this flight to about two metres. Another model, exhibited before the same society in October, 1874, flew in an horizontal line, vertically upward, and also ascended obliquely.

On the 27th of last November, at a public exhibition, this model flew from one end to the other of the hall of the Horticultural Society (see Aéronaute, February, 1875). On the 2d of July, 1875, it performed with success before the French Physical Society. The velocity of its flight is from five to seven metres per second.

The birds of twisted caoutchouc have been a great success.

M. Hureau de Villeneuve, whose zeal in the study of aërial navigation is well known, and who in his many contributions to the theory of flight since 1868 has discussed the inclination to the horizon of the axes of the scapulo-humeral articulations and their posterior convergence, exhibited, on the 20th of June, 1872, a bird moved by twisted caoutchouc, which, he states, elevated itself vertically to a height of nearly one metre. Continuing his researches with perseverance, he again exhibited his apparatus before the Society of Aërial Navigation on the 13th of January, 1875, after having supplied it with wings