THE DOMINION OF THE AIR.
THOSE who have studied the recent developments of aeronautics are confident that the outstanding achieve- ment of the twentieth century will be the solution of the
problem of human flight, which may be defined as the possi- bility of free locomotion through the air in a definite direction under any meteorological conditions. The annual meeting of the International Commission of Aeronauts, held at Brussels at the end of last week, gives us an opportunity of taking stock of recent advances in this direction. The most obvious of these is the acquisition by at least three of the Great Powers of navigable balloons which promise to be a notable addition to their military plant. Although a veil of official secrecy is naturally drawn over tho experiments of the War Offices, it seems to be clear that the Lebaudy balloon which has been adopted by the French Army, and the Parseval airship of the Germans, have both proved them- selves to be perfectly efficient within their necessary limits. The navigable balloon which has been constructed by our own military Balloon Department made a trial trip last week which was satisfactory for a first attempt, although it indicates that the British airship is not yet so well under control as the foreign ones. This might have been expected, in view of the fact that the experiments in navigating balloons which have been carried on since Henri Giffard built the first dirigible balloon in 1852 have been almost entirely undertaken on the Continent In Giffard's day it was impossible to con- struct a motor sufficiently light in relation to its power to be successfully applied to so unwieldy a fabric as a balloon. This was true even when the French military airship of Renard and Krebs, in 1884, performed for the first time the feat of making several journeys in which it successfully returned to the starting-point,—the sole test of a practicable machine of the kind. Its achievements, which have only been surpassed within the last few years, were all the more creditable to the distinguished military engineers who constructed it because they were forced to use a heavy eleotro•motor which weighed more than half-a-ton and only developed eight and a half horse-power. The growth of the motor-car industry, with the concurrent demand for very light and powerful engines, has greatly simplified the task of the aerial navigator, who can now obtain engines which give a horse-power for every five or six pounds of weight. It is thus possible to equip a balloon of moderate size with a motor which will drive it at a speed of twenty or thirty miles an hour in still air, and this is the fundamental fact which has made balloon navigation a serious possibility.
We may take it as proved, then, that an airship, consisting of a cylindrical balloon with a motor attached, can be built which will travel at twenty to thirty miles an hour in calm weather. It is true that the management of such a vessel requires a high degree of skill, and that there are considerable difficulties in the way of persuading it to maintain an even keel. But the performances of the Lebaudy and Parseval balloons show that the primary obstacle in the way of aerial navigation has been overcome. It remains, however, to inquire whether this is tantamount to the solution of the flight problem, as some hasty thinkers have claimed. We have just had a practical warning from the frozen North that it is by no means so. Mr. Wellman's airship, which seems to have been as powerful and as speedy as any of those yet made in Europe, had a very narrow escape from disaster on its first trip. The report of its performance tells us that the steering- gear worked well, and that the airship attained so great a speed that the attendant steamer could not keep up with it. But the moment that a squall broke over the balloon its powerlessness to combat adverse meteorological conditions was made manifest. Fortunately this test occurred at the very outset of its voyage, and the aeronauts were able to land on a glacier adjoining the coast of Spitsbergen, from which they were rescued in time. But there can be little doubt that if Mr. Wellman had been favoured with fine weather for the first few hours of his adventurous expedition, his enterprise would have ended in the same painful obscurity which still hangs over the fate of Andree. The obvious con- clusion is that the navigable balloon is not as yet a practical means of navigation : it is only a fine-weather toy. This has long been argued by scientific students of aeronautics. The anemometers on the platform of the Eiffel Tower have shown that the average speed of the wind at that moderate elevation is eighteen miles an hour. Therefore it follows that a navigable balloon, in order to be capable of making its voyage independent of an average wind, must be able to travel at least forty miles an hour in still air,—that is, it would then make twenty miles an hour against an average current of air, and no smaller speed is admissible for a serious aid to locomotion in these days. But at forty miles an hour the resistance of the atmosphere becomes a very serious factor, as any one who has travelled at that speed on a motor- car will readily admit. M. Banet-Rivet, who has made a careful study of the problem of air-resistance in relation to cylindrical or cigar-shaped balloons, maintains that no known fabric of which balloons are constructed is capable of pre- serving its shape or texture for any length of time at such a speed. Only a metallic hull, like that of a ship, could endure the strain, and the weight of such a hull is immediately pro- hibitive. Thus both the argument of the engineer and the experience of the practical aeronaut combine to tell us that the navigable balloon has a natural limit set to its usefulness, and must remain at the mercy of the wind whenever it blows with more than average speed. The conclusion is that navigable balloons must remain mere toys, suitable perhaps for the purposes of sport or of military reconnaissance, but in no sense practical aerial vehicles for passenger traffic or exploration.
We are thus brought rigorously bank to the belief, already reached on other lines by investigators, that the problem of flight must be solved without the help of the balloon. There may be a distinguished future before the airship in warfare—. especially if the Hague Conference agrees to relax the pro- hibition of 1899 against its use as an engine of offence—or as a safety-valve for scorching motorists who grow tired of dusty roads, popular contumely, and police attention. But the serious aspirant to travel through the air holds that the balloon, for all the good work which it has done in the past century, has been in reality an obstacle to aeronauts, since it has diverted their attention from the right path. We find nothing like a balloon in Nature : all birds and other flying creatures are heavier than the air which they displace, and depend for their support in the air on wind-pressure against the under surface of their wings. This is the model which the designer of a practical flying-machine must set before himself, though, of course, that particular argument is not conclusive, for Nature also ignores the wheel. But theory and practice alike point to the adoption of the aeroplane, or true flying- machine, as necessary before we can solve the problem of flight. Theory, as illustrated in the investigations of Langley and his colleagues, shows that a properly designed aeroplane, moving through the air with a considerable velocity, can support much greater weights than any balloon ever yet constructed, and that it has the remarkable property of needing less pro- portionate power to keep it going as its speed increases, therein differing from any other method of locomotion known to us. There is good scientific warrant for believing that the construction of a trustworthy aeroplane may revolutionise our ideas of possible speed in travel, bringing London within two hours of Paris and two days of New York. At present there is one grave obstacle in the way of building practical flying- machines,—the difficulty of ensuring their balance in the air, an art which the bird has imperfectly learnt through countless generations of practice and inherited instinct. The Wrights are as yet the only aeronauts who claim to have mastered this difficulty, even on a small scale; but their persistent refusal to submit their machine to competent critics makes it impossible to pronounce on the validity of their claim. But to those who are familiar with the history and present position of aeronautics there is little room for doubt that man will master the dominion of the air within the present century,— perhaps within our own lifetime. There is hardly any more fascinating prospect for the enthusiast, though its con- sequences may give the philosopher pause.
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