Fig. 479.—Back view of apparatus.
But the wing does not only move as a whole; every part of it, particularly as it rises, shows a tendency to inclination, which is most marked towards the extremity; the part near the body alone preserves an invariable obliquity. M. Tatin was of opinion that it is with the screw that it is necessary to direct the twisting movement; and to obtain it with all its transitions, he has substituted for silk wings, which fold up, some wings composed entirely of strong feathers, arranged in such a manner that they slipped one over the other when in motion. The arrangement was perfect, but still not suitable for adaptation to the large bird. The inventor therefore again returned to the use of the silk wings, which he appears to have definitely adopted. By means of certain modifications which he has recently introduced in his larger apparatus—viz., a change in the shape of the wings, variation of the amplitude in the flapping, etc., M. Tatin has been enabled to make great progress. The bird, acting by means of compressed air, at first could only raise three-quarters of its own weight, but finally lifted itself entirely. And we must take into consideration that the apparatus has to struggle against the weight of the steering apparatus, which nullifying the vertical and horizontal reactions of the bird during flight, constantly fulfils the office of regulator.
We will now pass to the consideration of two ingenious appliances of a very clever inventor, M. Salleron.
Small Atmospheric Boat.
The little boat shown in fig. 480, which is about the size of an ordinary plaything, is a very ingenious, if not a practical, application of the specific lightness of air acting as a propelling force. In this instance steam plays but a secondary part, which consists in carrying off the air that causes the moving of the boat.
Fig. 480.—Atmospheric boat.
The apparatus, as represented in fig. 481, is of extreme simplicity, as will be seen at a glance. A small cylindrical boiler, B, connected with a capillary tube, is placed on two supports over a spirit-lamp, in such a manner that the opening from which the steam issues is directly opposite the mouth of the tube, T. This tube, after forming a sudden inclination, terminates at the back of the boat in an inclined drain, R. The steam driven through the tube, T, carries along with it a certain quantity of air, which, forced under the water, propels the boat along. The little vessel soon reaches considerable speed, leaving a long track behind it. It will be seen that this is not a mechanical apparatus, capable of absorbing force or diminishing the action of steam by causing its condensation.