BOOKS.
HUMAN FLIGHT.*
THE authors of this entertaining volume have given us a popular and most admirably illustrated, though somewhat ill- arranged and unscientific, history of aerial navigation. Many think that we are on the verge of a solution of the great problem of human flight, by which is meant the ability to make an aerial journey in a definite direction. Mankind has long dreamt vaguely of such an achievement, but it is little more than a century since the first steps towards it were made by science. The authors of the book now before us pass hastily over the mediaeval records of flying machines, which might repay a closer study than they have yet received. One would like to know if there was any reality underlying the countless variations of the belief in the flying powers of mediaeval witches, and whether it was solely by what Sir Thomas Browne calls "the courteous revelation of spirits" that Roger Bacon anticipated the principle of the Montgolfier balloon, and Leonardo da Vinci filled a page of his notebook—here repro- duced—with designs that suggest some of the aeroplanes of Langley, Maxim, and Chanute. Perhaps we never shall know; certainly Messrs. Valentine and Tomlinson have not attempted to throw light on this part of the subject. Their record prac- tically begins with the discovery of the Montgolfiers. They relate .an interesting and not generally known anecdote, to the effect that the first notion of the hot-air balloon was suggested by Madame Montgolfier's silk petticoat. "The lady had stretched it upon a light wicker pannier near the fire to dry. The increasing hot air suggested to her husband an intentional acceleration, and to Madame's astonishment the garment began to rise to the ceiling, thereby demonstrating the soundness of her husband's scientific principles, and led to the making of the pioneer linen balloon ! " We fear that this interesting aneolote, which is told in the slovenly manner unfortunately characteristic of the authors' writing, must be relegated to the same fabulous limbo as the tales of Newton's apple and Watt's kettle; the Memoirs of the Montgolfiers themselves show that it was not in this accidental fashion that they hit upon one of the most striking of discoveries. From the balloon which first ascended at Paris on June 5th, 1783, sprang the long succession of experiments in this branch of aeronautics of which M. Santos-Dumont has furnished the latest and most advanced instances. Of these a fairly full account is to be found in the present volume, though the authors fail to distinguish adequately between ideas which came to nothing and inventions which really advanced the study of aeronautics.
For more than fifty years after Pillar() de Rozier made the first ascent into the air no one attempted seriously to direct the course of a balloon. The only plan which commended itself to the early aeronauts was to seek a favourable current by manceuvring their balloons in a vertical direction. As each rise involved the loss of ballast and each descent the loss of gas, a speedy limit was fixed to the duration of such voyages, which at the best were entirely dependent on the chance of finding a favourable breeze in some accessible stratum of the atmosphere. The first really navigable balloon was that in which Henri Giffard ascended at Paris in 1852. With a cigar-shaped balloon and a steam-driven screw he succeeded in making a headway of five to seven miles an hour, "which enabled him to execute various manceuvres of circular motion with perfect success," though it was obviously impossible for him to return to his starting-point in any weather but a dead calm The first dirigible balloon which actually did return to its place of departure was the French military balloon of MM. Renard and Krebs, 'La France,' which performed that feat at Meudon on August 9, 1884 The authors give a very inade- quate account of that experiment, though the secrecy which the _ • Tiaras la Specs. By E. Seton Valentine and E. L. Tomlinson. Illustrated. London: Hurst and Blackett. ElOs. 6d. net.]
French Government—for military reasons—has preserved with regard to its details and those of later work on the same lines is some excuse for this. The third great step in the steering of balloons was taken by M. Santos-Dumont, whose brilliant achievements are fresh in the memory of our readers, and have just been partially repeated in London by Mr. Stanley Spencer.
In the preface which Sir Hiram Maxim contributes to this volume—which, though brief, contains more of scientific value than all the rest of the book—he gives the reasons which appeal to most students of aeronautics for believing that M. Santos-Dumont has come very near the limit of the dirigible balloon's possibilities :—
"A balloon in the very nature of things has to be very light and fragile, otherwise it would not rise in the air. Its mean density is, therefore, less than the air that it displaces, in other words, a mere bubble. If it were possible to make motors which would develop 100-horse power to every pound of weight, it would still be quite impossible to navigate a balloon, no matter how well made, against even a moderate breeze. It is not possible to make a balloon strong enough to be driven through the air at any considerable speed, and at the same time light enough to rise in the air; therefore balloons must always be at the mercy of a wind no greater than that which prevails at least 300 days in the year."
At the same time, it does not follow that such navigable balloons as M. Santos-Dumont has constructed, or as are believed to be in the possession of at least two of the great Continental Armies, may not be of considerable use in war, at least as scouting machines, besides lending themselves to the aims of sport. In the latter respect, it has been suggested that M. Santos-Dumont will indeed be a benefactor of man- kind if he diverts the devotees of racing motor-cars from the French roads which they make so dangerous and dusty to the middle air.
The real future of aerial navigation lies with the flying machine, which is heavier than the air, and imitates the bird in keeping itself afloat by virtue of the speed with which it is travelling against the wind. At present, indeed, its investigators are checked by the initial difficulty which Nature has put in their way, since such a machine, if anything goes wrong with it during flight, is bound to come rushing down like a shot pheasant. "Those who seek to navigate the air have not even made a start as yet," says Sir Hiram Maxim, "and the possibilities before them are very great indeed." Many flying machines, of course, have actually flown for greater or less distances. The " albatross " of Le Bris—if we can rely on the account of its achievements, which is rather doubtful —and the artificial birds of Penaud, Pichancourt, Trouve, and others, have shown the accuracy of their principle. Still more successful has been the "aerodrome" of Professor Langley, which has flown for half a mile at a time, driven by a steam-engine, and has descended without injury. A picture of that ingenious machine forms the frontispiece to this volume. Sir Hiram Maxim's own aeroplane, the only flying machine which has yet been constructed on scientific prin- ciples and on a large scale, would undoubtedly have flown if it had been allowed to escape from its guide-rails. But the trouble is that all such machines, though the question of an adequate motive-power is already solved, are unable to steer themselves instinctively as birds do, and for a man to under- take to keep them balanced in the air is rather more dan- gerous than plunging into Niagara Rapids after a course of swimming lessons on dry land. The fate of Lilienthal and his disciple Filcher, who undertook the preliminary task of study- ing the art of aerial balance in "soaring machines "—artificial
wings or aeroplanes devoid of motive-power—is a warning to adventurers, though Mr. Chanute has apparently shown that
much of the danger to which they succumbed may be elimi- nated. Sir Hiram Maxim, though he has admitted that this essential problem of balance has so far beaten him, is confident that "everything is working in the direction of an early solution of the problem." Probably the twentieth century will see man's conquest of the air ; but it remains to be seen whether the gain will be a fair return for the lives and treasure that will need to be expended on it.
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