Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/335

 FLIGHT 323 pound. The model was forced by its propellers along a wire at a great speed, but so far as an observer could determine, failed to lift itself, notwithstanding its extreme lightness and the comparatively very great power employed. Mr Stringfellow stated that his machine occasionally left FIG. 44. Stringfellow s Flying Machine (1868). the wire and was sustained by its aero-planes alone. The horizontal speed attained was certainly very great ; but as the machine was exhibited under cover in the Crystal Palace buildings, and ran along a wire, it is doubtful how it would have deported itself in the open air. Everything about it was rigid, the aero-planes, screws, &c. ; and as the dead surfaces displayed were comparatively very large, the chances are that it would not have been able to hold its own against air currents. That the principle of its construc tion was faulty is proved beyond doubt by the fact that it weighed under 12 Ib, while its engine exerted a third of a horse power. No flying creature, as is well-known, weigh ing 12 Ib possesses a tithe of the power indicated. This fact is significant as showing that flight is not a mere question of levity and power. As has been more than once stated in the present article, the mystery of flight can only be cleared up by an intelligent study of the structure and mode of application of the flying organs of animals. It is to natural flight and the principles which underlie it that the aeronaut must look for a solution of the intensely interesting but vastly complicated problem of aerial navi gation. The idea embodied by Henson, Wenham, and String- fellow is plainly that of a boy s kite sailing upon the wind. The kite, however, is a more perfect flying apparatus than that furnished by these gentlemen, inasmuch as the inclined plane formed by its body strikes the air at various angles the angles varying according to the length of string, strength of breeze, length and weight of tail, &c. Hen- son s, Wenham s, and Stringfellow s methods, although carefully tried, have hitherto failed. The objections are numerous. In the first place, the supporting planes (aero planes or other forms) are not flexible and elastic as wings are, but rigid ; 2d, they strike the air at a given angle, where, again, there is a departure from nature; 3d, a machine so constructed must be precipitated from a height or driven along the surface of the land or water at a high speed to supply it with initial velocity ; 4th, it is unfitted for flying with the wind unless its speed greatly exceeds that of the wind ; 5th, it is unfitted for flying across the wind because of the large surfaces exposed; 6th, the sustain ing surfaces are passive or dead surfaces, i.e., they have no power of moving or accommodating themselves to altered circumstances. Natural wings, as explained, present small flying surfaces, and these can be applied to the air at any degree of obliquity the great speed at which wings are propelled converting the spaces through which they pass into what are practically solid bases of support, as indicated at pp. 310, 313 (figs. 9, 20, 21, 22, and 23). This arrangement enables natural wings to seize and utilize the air, and renders them superior to adventitious currents. Natural wings work up the air in which they move ; but unless the volant animal desires it, they are scarcely, if at all, influenced by winds or currents which are not of their own forming. In this respect they differ entirely from the balloon and all forms of fixed aero-planes. In nature small wings driven at a high speed produce the same result as large wings driven at a low speed. In flight a certain space must be covered, either by large wings spread out as solids, or by small wings made to vibrate rapidly. A like result is obtained if air currents travelling at a high speed strike the under surfaces of the wings of the volant animal. In the former cases the wings are active, the air passive ; in the latter case the air is active and the wings passive. It would be easy to multiply almost indefinitely our list of aerial models and flying machines. 1 As however the present article has already attained sufficiently large dimen sions it will suffice if we refer in conclusion to the aerial steamer of Mr Moy, designed in 1874, and still in process of construction. Its leading features will readily be under stood by a reference to the annexed drawing (fig. 45). . FIG. 45. Moy s Aerial Steamer (1874). Mr Moy s invention consists of a light, powerful, skeleton frame resting on three wheels ; a very effective light engine constructed on a new principle, which dispenses with the old-fashioned, cumbrous boiler ; two long, narrow, horizontal aero-planes ; and two comparatively very large aerial screws, The idea is to get up the initial velocity by a preliminary run on the ground. This accomplished it is hoped that the weight of the machine will gradually be thrown upon the aero-planes in the same way that the weight of certain birds the eagle, e.g. is thrown upon the wings after a few hops and leaps. Once in the air the aero-planes will become effective in proportion to the speed attained. Mr Moy s machine resembles in its general features that of Mr Stringfellow. It repeats its defects as far as rigid surfaces are concerned, but it has the advantage in presenting a relatively less amount of surface. The diminished surface of Mr Moy s machine is, moreover, more broken up, and what is important, a relatively greater proportion of the surface (so diminished and broken up) is made active or moving surface. These are hopeful features. The unremitting efforts of Mr Moy and other British engineers to construct flying machines deserve well of science. They are significant as showing that the great subject of aerial navigation is at length receiving a fair share of the thought and energy of a country which has already produced the locomotive engine, and which, there is good reason to believe, is destined also to produce the flying machine. ( J - B - p -) 1 The most recent experiments in aerial transit are described in the Transactions of the New Zealand Institute, vol x., 1878.