So far Wilkins went; and he went no farther. His speculations, however, made a deep impression on his own age, gave a bias to the researches of his fellows, and, incidentally, aroused a storm of ridicule. When Joseph Glanvill, in his vigorous little treatise calledScepsis Scientifica(1665), wrote a forecast of the possible achievements of the Royal Society, he borrowed his hopes from Wilkins. 'Should these heroes go on', he says, 'as they have happily begun, they will fill theworld with wonders, and posterity will find many things that are now but rumours, verified into practical realities. It may be, some ages hence, a voyage to the southern unknown tracts, yea, possibly the Moon, will not be more strange than one to America. To them that come after us it may be as ordinary to buy a pair of wings to fly into remotest regions, as now a pair of boots to ride a journey. And to confer at the distance of the Indies, by sympathetic conveyances, may be as usual to future times, as to us in a literary correspondence. The restoration of grey hairs to juvenility, and renewing the exhausted marrow, may at length be effected without a miracle; and the turning the now comparative desert world into a paradise, may not improbably be expected from late agriculture.' Again, when Sir William Temple, some thirty years later, cast contempt upon the Moderns in hisEssay of Ancient and Modern Learning, it was the speculations of Wilkins that provoked his keenest satire. 'I have indeed heard of wondrous Pretensions and Visions of Men, possess'd with Notions of the strange Advancement of Learning and Sciences, on foot in this Age, and the Progress they are like to make in the next; as, the Universal Medicine, which will certainly cure all that have it; the Philosopher's Stone, which will be found out by Men that care not for Riches: the transfusion of young Blood into old Men's Veins, which will make them as gamesome as the Lambs, from which 'tis to be derived; an Universal Language, which may serve all Men's Turn, when they have forgot their own: the Knowledge of one another's Thoughts, without the grievous Trouble of Speaking: the Art of Flying, till a Man happens to fall down and break his Neck: Double-bottom'd Ships, whereof none can ever be cast away, besides the first that was made: the admirable Virtues of that noble and necessary Juicecalled Spittle, which will come to be sold, and very cheap, in the Apothecaries' Shops: Discoveries of new Worlds in the Planets, and Voyages between this and that in the Moon, to be made as frequently as between York and London: which such poor Mortals as I am think as wild as those of Ariosto, but without half so much Wit, or so much Instruction; for there, these modern Sages may know where they may hope in Time to find their lost Senses, preserved in Vials, with those of Orlando.'
Both Sir William Temple and Joseph Glanvill were men of acute intelligence and complete sanity; the one an aged statesman deeply versed in the deceits and follies of men; the other a young cleric, educated in the Oxford of the Commonwealth, and stirred to enthusiasm by what he had there heard of the progress of natural philosophy. In this perennial debate the man of the world commonly triumphs; he plays for the stakes that are on the table, and does not put faith in deferred gains. For something like two hundred years Sir William Temple's triumph was almost complete. Now things have changed, and Glanvill's rhapsody comes nearer to the truth. Wireless telegraphy, radium, the discoveries of bacteriology, and not least the conquest of the air, have taken the edge off the sallies of the wit, and have verified the dreams of the prophet.
What most delayed the science and art of flight, which made no progress during the whole of the eighteenth century, was an imperfect understanding of the flight of birds. The right way to achieve flight, as events were to prove, was by the study and practice of gliding. But birds were believed to support, as well as to raise, themselves in the air chiefly by what in the jargon of science is called orthogonal flight, that is, by direct downward flapping of the wings. This view received authoritative support from a famous treatisewritten in the seventeenth century by Giovanni Alfonso Borelli, an Italian professor of mathematical and natural philosophy. Borelli, who held professorships at the Universities of Florence and Pisa, and corresponded with many members of the Royal Society, was an older man than Wilkins, but his book on the movements of animals (De Motu Animalium), which included a section on the flight of birds (De Volatu), was not published till 1680, when both he and Wilkins were dead. It was long held in high esteem for its anatomical exposition of the action of flying, and some of its main contentions cast a damp upon the hopes of man. The bones of a bird, says Borelli, are thin tubes of exceeding hardness, much lighter, and at the same time stronger, than the bones of a man. The pectoral muscles, which move the wings, are massive and strong—more than four times stronger, in proportion to the weight they have to move, than the legs of a man. And he states his conclusion roundly—it is impossible that man should ever achieve artificial flight by his own strength. This view, dogmatically stated by one who was a good mathematician and a good anatomist, became the orthodox view, and had an enduring influence. All imitation of the birds by man, and further, all schemes of navigating the air in a machine dynamically supported, seemed, by Borelli's argument, to have been thrust back into the limbo of vanities.
There remained only the hope that some means might be found of buoying man up in the air, thereby leaving him free to apply his muscular and mechanical powers to the business of driving himself forward. Another celebrated treatise of the seventeenth century pointed the way to such a means. Francesco Lana, a member of the Society of Jesus in Rome, spent the greater part of his life in scientific research. He planned a large encyclopaedia, embodying all existing science, in so far as it was based on experiment and proof. Of thiswork only two volumes appeared during his lifetime; he died at Brescia in the year 1687. But long before he died, he had produced, in 1670, a preliminary sketch of his great work; and it is this earlier and shorter treatise which contains the two famous chapters on the Aerial Ship. The aerial ship is to be buoyed up in the air by being suspended from four globes, made of thin copper sheeting, each of them about twenty-five feet in diameter. From these globes the air is to be exhausted, so that each of them, being lighter than air, will support the weight of two or three men. The ship being thus floated can be propelled by oars and sails.
Any modern reader, without asking for further specifications, can pronounce this design absurd. Lana was prevented by his vow of poverty from spending any money on experiment, so that he had to meet only argumentative objections, not those much more formidable obstacles, the ordeal of the inventor, which present themselves when a machine is theoretically perfect and will not work. The difficulties which he foresaw are real enough. The process of exhausting the air from the globes might, he thought, prove troublesome. The pressure of the atmosphere on the outer surface, it might be held, would crush or break the globes, to which he replied that that pressure would be equal on all sides, and would therefore rather strengthen the globes than break them. The ship, some might object, could not be propelled by oars; Lana thinks it could, but suggests, to comfort the objectors, that oars will rarely be necessary, for there will always be a wind. The weight of the machine and of the persons in it will fortunately prevent it from rising to heights where breathing becomes impossible. 'I do not foresee', says Lana, 'any other difficulties that could prevail against this invention, save one only, which to me seems the greatest of them all, and that is that God would never surely allow sucha machine to be successful, since it would create many disturbances in the civil and political governments of mankind. Where is the man who can fail to see that no city would be proof against surprise, when the ship could at any time be steered over its squares, or even over the courtyards of dwelling-houses, and brought to earth for the landing of its crew?... Iron weights could be hurled to wreck ships at sea, or they could be set on fire by fireballs and bombs; nor ships alone, but houses, fortresses, and cities could be thus destroyed, with the certainty that the airship could come to no harm as the missiles could be hurled from a vast height.'
The extravagance of Lana's design must not be allowed to rob him of the credit of being, in some sense, the inventor of the balloon. A balloon filled with gas, and lighter than air, was in his day inconceivable; the composition of the atmosphere was unknown, and the chemistry of gases was not understood. But he had followed the physical investigations of the seventeenth century, and was well acquainted with Torricelli's demonstration of the weight of the atmosphere. The only practical way for him to make a vessel lighter than air was to empty it of the air within it, and Torricelli's invention of the barometer seemed to bring such a device within reach. The common pump begat the barometer; the barometer begat the balloon. But the enormous pressure of the atmosphere on a vessel encasing a vacuum, though Lana had triumphed over it in argument, could not be so easily dealt with in practice. The success of the balloon was delayed until, by the discovery and production of a gas lighter than air, a frail and thin envelope could be supported against the pressure from without by an equal pressure from within.
For ballooning what was chiefly necessary was a thorough knowledge of gases and of the means ofproducing them. The older chemistry, or alchemy, devoted all its attention, for centuries, to the precious metals, and knew nothing of gas. Medical chemistry, which succeeded it, was concerned chiefly with the curative properties of various chemical preparations. When Robert Boyle, and the investigators who came after him, put aside this age-long preoccupation with wealth and healing, and set themselves to determine, by observation and experiment, the nature of common substances, and the possibility of resolving them into simpler elements, modern chemistry began. Four states of matter, namely, earth, air, fire, and water, were recognized by the older chemists, and were by them called elements; it was the work of the eighteenth century to investigate these, and especially to separate the constituents of air and of water. In 1774 Joseph Priestley discovered oxygen. In 1782 Henry Cavendish showed that hydrogen, when burnt, produces water. At a much earlier date hydrogen had been produced by the action of acid on metals, and had been found to be many times lighter than air. Dr. Joseph Black, professor of chemistry in the University of Edinburgh, was the first to suggest, in 1767, that a balloon inflated with hydrogen would rise in the air; and the experiment was successfully tried with soap-bubbles by Tiberius Cavallo, in the year 1782.
Nevertheless, the famous first balloon, which ascended in 1783, was not filled with hydrogen, and was invented by what may be called a happy accident. The brothers Joseph and Jacques Montgolfier were the sons of a wealthy paper-maker at Annonay, not very far from Lyons. The suggestion of their balloon came to them from observing that thick opaque clouds float high in the air. Linen material was readily accessible to them at the factory, and they resolved to try whether a large balloon, some thirty-three feet in diameter, filled with smoke vapours, would rise in theair. Their experiment was successful. On the 5th of June 1783 they filled their balloon with smoke (and therefore with hot air) over a fire of chips and shavings; it rose easily, and travelled to a distance of about a mile and a half before it cooled and sank. The fame of this experiment quickly reached Paris, the centre of science and fashion, and awakened rivalry. Under the direction of Professor Charles, a well-known physicist, two brothers whose surname was Robert made from varnished silk a balloon of about thirteen feet in diameter; it was filled with hydrogen, and on the 27th of August 1783, in the presence of a large and excited assembly, it rose from the Champ de Mars and travelled some fifteen miles into the country, where it fell, and produced a panic among the peasantry. On the 19th of September Joseph Montgolfier was brought to Versailles to give a demonstration of his new invention in the presence of the King and Queen. On this occasion his balloon rose 1,500 feet into the air, carrying with it a sheep, a cock, and a duck, the first living passengers, whom it deposited unhurt when it came to ground again after a short flight. Thereafter society went balloon-mad. Pilâtre de Rozier, a young native of Metz, determined to attempt an aerial voyage. During the month of October he experimented with a captive balloon of the Montgolfier type, from which he suspended a brazier, so that by a continued supply of heated air the balloon should maintain its buoyancy. On the 21st of November 1783, accompanied by the Marquis d'Arlandes, he rose in a free balloon from the Bois de Boulogne, and made a successful voyage of twenty minutes, during which time he travelled over Paris for a distance of about five miles. Ten days later, on behalf of the savants, M. Charles retorted with a voyage of twenty-seven miles, in a hydrogen balloon, from Paris to Nesle; he was accompanied by one of the brothers Robert, and when Robert left the car atNesle the balloon, lightened of a part of its burden, rose rapidly with M. Charles to a height of two miles in the air. Most of the fittings of the modern hydrogen balloon, the hoop and netting, for instance, from which the car is suspended, and the valve at the top of the balloon for the release of the gas, were devised by Charles. The unfortunate Pilâtre de Rozier met his death on the 15th of June 1785, in an attempt to cross from Boulogne to England. In order to avoid a constant wastage of hydrogen in controlling the height of the balloon, he devised a double balloon; the larger one, above, was filled with hydrogen, the smaller one, below, was worked with hot air from a brazier, on the Montgolfier principle. At a height of some three thousand feet, while it was still over French territory, the double balloon caught fire and fell flaming to the earth.
The earliest balloon ascents in England followed close upon the French experiments. On the 25th of November 1783 Count Francesco Zambeccari sent up an oil-silk hydrogen balloon, ten feet in diameter, from the Artillery Ground in Moorfields; it travelled forty-eight miles, and fell at Petworth in Sussex. On the 22nd of February 1784 a balloon of five feet in diameter, liberated at Sandwich in Kent, travelled seventy-five miles, and after crossing the Channel, fell at Warneton in Flanders. To inflate a bag with gas and let it take its chance in the air is no great achievement, but these were flights of good promise. The first person in Great Britain to navigate the air was James Tytler, a Scot, who on the 27th of August 1784 ascended in a fire-balloon, that is, a balloon filled with hot air, from Comely Gardens, Edinburgh, and travelled about half a mile. Tytler had been employed by the booksellers to edit the second edition of theEncyclopaedia Britannica, of which he wrote the greater part, at a salary of seventeen shillings a week; he passed hislife in poverty, and his balloon adventure attracted little attention. The public mania for ballooning as a spectacle began with the ascents of Vincenzo Lunardi, secretary to the Neapolitan ambassador in England. Lunardi's first ascent, which was well advertised, was made from the Artillery Ground in Moorfields on the 15th of September 1784, in the presence of nearly two hundred thousand spectators. His hydrogen balloon, of about thirty-two feet in diameter, sailed high over London, and descended near Ware in Hertfordshire. His record of his sensations, written in imperfect English, and published in 1784 under the title ofAn Account of the First Aerial Voyage in England, deserves quotation:
'At five minutes after two, the last gun was fired, the cords divided, and the Balloon rose, the company returning my signals of adieu with the most unfeigned acclamations and applauses. The effect was that of a miracle on the multitudes which surrounded the place; and they passed from incredulity and menace into the most extravagant expressions of approbation and joy.
'At the height of twenty yards, the Balloon was a little depressed by the wind, which had a fine effect; it held me over the ground for a few seconds, and seemed to pause majestically before its departure.
'On discharging a part of the ballast, it ascended to the height of two hundred yards. As a multitude lay before me of a hundred and fifty thousand people, who had not seen my ascent from the ground, I had recourse to every stratagem to let them know I was in the gallery, and they literally rent the air with their acclamations and applause. In these stratagems I devoted my flag, and worked with my oars, one of which was immediately broken and fell from me. A pigeon too escaped, which, with a dog, and cat, were the only companions of my excursion.
'When the thermometer had fallen from 68° to 61°I perceived a great difference in the temperature of the air. I became very cold, and found it necessary to take a few glasses of wine. I likewise eat the leg of a chicken, but my bread and other provisions had been rendered useless by being mixed with the sand which I carried as ballast.
'When the thermometer was at fifty, the effect of the atmosphere, and the combination of circumstances around, produced a calm delight, which is inexpressible, and which no situation on earth could give. The stillness, extent, and magnificence of the scene rendered it highly awful. My horizon seemed a perfect circle; the terminating line several hundred miles in circumference. This I conjectured from the view of London; the extreme points of which, formed an angle of only a few degrees. It was so reduced on the great scale before me, that I can find no simile to convey an idea of it. I could distinguish Saint Paul's and other churches, from the houses. I saw the streets as lines, all animated with beings, whom I knew to be men and women, but which I should otherwise have had a difficulty in describing. It was an enormous beehive, but the industry of it was suspended. All the moving mass seemed to have no object but myself, and the transition from the suspicion, and perhaps contempt, of the preceding hour, to the affectionate transport, admiration and glory of the present moment, was not without its effect on my mind. I recollected the puns[3]on my name, and was glad to find myself calm. I had soared from the apprehensions and anxieties of the Artillery Ground, and felt as if I had left behind me all the cares and passions that molest mankind.
'Indeed, the whole scene before me filled the mind with a sublime pleasure, of which I never had a conception.The critics imagine, for they seldom speak from experience, that terror is an ingredient in every sublime sensation. It was not possible for me to be on earth in a situation so free from apprehension. I had not the slightest sense of motion from the Machine, I knew not whether it went swiftly or slowly, whether it ascended or descended, whether it was agitated or tranquil, but by the appearance or disappearance of objects on the earth. I moved to different parts of the gallery, I adjusted the furniture, and apparatus, I uncorked my bottle, eat, drank, and wrote, just as in my study. The height had not the effect, which a much lesser degree of it has near the earth, that of producing giddiness. The broomsticks of the witches, Ariosto's flying-horse, and even Milton's sunbeam, conveying the angel to the earth, have all an idea of effort, difficulty, and restraint, which do not affect a voyage in the Balloon.
'Thus tranquil, and thus situated, how shall I describe to you a view, such as the ancients supposed Jupiter to have of the earth, and to copy which there are no terms in any language. The gradual diminution of objects, and the masses of light and shade are intelligible in oblique and common prospects. But here every thing wore a new appearance, and had a new effect. The face of the country had a mild and permanent verdure, to which Italy is a stranger. The variety of cultivation, and the accuracy with which property is divided, give the idea ever present to a stranger in England, of good civil laws and an equitable administration; the rivers meandering; the sea glist'ning with the rays of the sun; the immense district beneath me spotted with cities, towns, villages, houses, pouring out their inhabitants to hail my appearance: you will allow me some merit at not having been exceedingly intoxicated with my situation.
'The interest which the spectators took in my voyage was so great, that the things I threw down were divided and preserved as our people would relicks of the most celebrated saints. And a gentlewoman, mistaking the oar for my person, was so affected with my supposed destruction, that she died in a few days.'
For many months after this the Flying Man was the chief topic of conversation in the town. Even in the previous year reports of the French ascents had produced a fever of excitement in London. 'Balloons', said Horace Walpole, writing in December 1783, 'occupy senators, philosophers, ladies, everybody.' All other interests yielded precedence. Miss Burney'sCeciliawas the novel of the season, but it had to give way. 'Next to the balloon,' said Mrs. Barbauld, in a letter written in January 1784, 'Miss Burney is the object of public curiosity.' A few weeks earlier, Dr. Johnson passed the day with three friends, and boasted to Mrs. Thrale that no mention had been made by any of them of the air balloon, 'which has taken full possession, with a very good claim, of every philosophical mind and mouth'. Some days after Lunardi's first ascent Johnson wrote to a friend, 'I had this day in three letters three histories of the flying man in the great Ballon. I am glad that we do as well as our neighbours.' Three letters were enough, and on the same day Johnson wrote to Sir Joshua Reynolds, 'Do not write about the balloon, whatever else you may think proper to say'. On the 29th of September 1784 Lunardi's balloon caught fire by accident, and was burnt on the ground. Johnson's quiet and sensible comment is conveyed in a letter to his friend Dr. Brocklesby, on the 6th of October: 'The fate of the balloon I do not much lament: to make new balloons is to repeat the jest again. We now know a methodof mounting into the air, and, I think, are not likely to know more. The vehicles can serve no use till we can guide them; and they can gratify no curiosity till we mount with them to greater heights than we can reach without; till we rise above the tops of the highest mountains, which we have yet not done. We know the state of the air in all its regions, to the top of Teneriffe, and therefore, learn nothing from those who navigate a balloon below the clouds. The first experiment, however, was bold, and deserved applause and reward.'
Johnson died in December of that same year; the balloon had made its appearance just in time for his comments. Another critic, Horace Walpole, was in two minds about balloons. Sometimes they seemed to him 'philosophic playthings'. He was growing old, and did not care to spend his time in 'divining with what airy vehicles the atmosphere will be peopled hereafter, or how much more expeditiously the east, west, or south will be ravaged and butchered, than they have been by the old clumsy method of navigation'. Yet in spite of his elegant indifference, he could not help being interested; and some of his divinations come very near to the truth. He pictures Salisbury Plain, Newmarket Heath, and all downs, arising into dockyards for aerial vessels; and he professes himself willing to go to Paris by air, 'if there is no air sickness'. The best defence of the new invention was spoken by Benjamin Franklin, who when he was asked in Paris, 'What is the use of balloons?' replied by another question—'What is the use of a newborn infant?'
The infancy of the balloon lasted long; indeed, if lack of self-control be the mark of infancy, the balloon was an infant during the whole of the nineteenth century. In the early days, new achievements, in distance or height, kept public expectation alive. JeanPierre Blanchard, a French aeronaut, and rival of Lunardi, succeeded, on the 7th of January 1785, in crossing the English Channel from Dover. Thereafter ascents became so numerous that it is impossible to keep count of them. Glaisher, writing about 1870, says that the most remarkable ascent of the century was that fitted out by Robert Hollond, Esq., M.P. The balloonist was Charles Green, and they were accompanied by Mr. Monck Mason, who published an account of the voyage. In Mr. Green's balloon, afterwards called theGreat Nassau, they left Vauxhall Gardens on the afternoon of Monday, the 7th of November 1836, with provisions to last a fortnight. They were soon lost in the clouds, and after crossing the sea, had no very clear idea of what country they were over. After eighteen hours' journey, fearing that they had reached Poland or Russia, they came to earth, and found that they had travelled five hundred miles, to the neighbourhood of the town of Weilburg, in the duchy of Nassau. Charles Green was the most experienced aeronaut of his time; he was the first to use coal-gas in place of hydrogen, and he was the inventor of the guide-rope, which is dropped from a balloon to allow her to be secured by a landing party, or is trailed on the ground to reduce her speed and to assist in maintaining a steady height.
The dangers of the balloon were diminished by the labours of scientific men, but its disabilities remained. No one who travelled in a balloon could choose his destination. The view of the earth, and of the clouds, obtainable from a height, was beautiful and unfamiliar, but in the absence of any specific utility the thing became a popular toy. In public gardens a balloon could be counted on to attract a crowd, and the showman soon gave it its place, as a miracle of nature, by the side of the giant and the dwarf, the living skeleton, and the fat woman. A horse is not seen to advantagein the car of a balloon, but it is a marvel that a horse should be seen there at all, and equestrian ascents became one of the attractions of the Cremorne Gardens in 1821.
It was not until 1859 that an organized attempt was made to reclaim the balloon for the purposes of science. In that year a committee, appointed by the British Association to make observations on the higher strata of the atmosphere, met at Wolverhampton. Volunteers were lacking until, in 1862, James Glaisher, one of the members of the committee, declared his willingness to prepare the apparatus and to make the observations from a balloon. Glaisher had spent many years on meteorological observation, in Ireland, at Cambridge University, and at the Royal Observatory, Greenwich. He proposed to investigate the effect of different elevations on the temperature of the dew-point; on the composition and electrical condition of the atmosphere, and on the rate and direction of the wind currents in it; on the earth's magnetism, and the solar spectrum; on sound, and on solar radiation. From 1862 to 1866 he made twenty-eight ascents, with Henry Coxwell as his balloonist. The most famous of these was from Wolverhampton on the 5th of September 1862, when Glaisher claimed to have reached a height of fully seven miles. After recording a height of 29,000 feet Glaisher swooned; Coxwell lost the use of his limbs, but succeeded in pulling the cord of the valve with his teeth. When Glaisher swooned the balloon was ascending rapidly; when he came to, thirteen minutes later, it was descending rapidly, and the height that he claimed was an inference, supported by the reading of a minimum thermometer. Critics have pointed out that his calculations made no allowance for the slackening of the upward pace of the balloon as it neared its limit, nor for the time it would take, with the valve feebly pulled, to change its direction and acquire speedin its descent. They are inclined to allow him a height of about six miles, which is a sufficiently remarkable achievement.
All these ascents, though they proved that the balloon had a certain utility for the exploration of the upper reaches of the atmosphere, did little or nothing for aerial navigation. The great vogue of the balloon distracted attention from the real problem of flight. That problem was not abandoned; a number of men, working independently, without any sort of public recognition, made steady advance during the whole course of the nineteenth century. By the end of the century, three years before flight was achieved, those who were most deeply concerned in the attempt knew that success was near. The great difficulty of scientific research lies in choosing the right questions to ask of nature. Every lawyer knows that it is easy to put a question so full of false assumptions that no true answer to it is possible; and many a laborious man of science has spent his life in framing such questions, and in looking for an answer to them. The contribution of the nineteenth century to the science of flight was that it got hold of the right questions, and formulated them more or less exactly, so that the answers, when once they were supplied by continued observation and experiment, were things of value.
The earliest of these pioneers was Sir George Cayley, a country gentleman with estates in Yorkshire and Lincolnshire, who devoted his life to scientific pursuits. He was born in 1773, and the balloons which excited the world during his boyhood directed his mind to the subject of aerial navigation. He invented many mechanical contrivances, and he laid great and just stress on the importance of motive power for successful flight. In 1809 he published, inNicholson's Journal, a paper on Aerial Navigation, which has since become a classic, for although it stops short of a completeexposition, it is true so far as it goes, and contains no nonsense and no fantasy. He endeavoured, in the first year of Queen Victoria's reign, to establish an aeronautical society, but the ill repute of the balloon and the bad company it kept deprived him of influential support. He did his duty by his county, as a Whig magnate, and amused his leisure with science, till his death in 1857.
Cayley's work is difficult to assess. He had all the right ideas, though the means of putting them into practice did not lie ready to his hand. If he had been a poor man, he might have gone farther. He designed, so to say, both an airship and an aeroplane; there was no one to execute his designs, and the scheme fell through. He more than once anticipated later inventions, but he put nothing on the market. His mind was fertile in mechanical devices, so that if one proved troublesome, he could always turn his attention to another. He is content to enunciate a truth, and to call it probable. 'Probably', he says, in discussing engines of small weight and high power, 'a much cheaper engine of this sort might be produced by a gas-light apparatus and by firing the inflammable air generated with a due portion of common air under a piston.' This is an exact forecast of the engine used to-day in all flying machines. He has some good remarks on the shape that offers least resistance to the air in passing through it, that is, on the doctrine of the streamline. He knew that the shape of the hinder part of a solid body which travels through the air is of as much importance as the shape of the fore-part in diminishing resistance. He does not seem to have known that it is of more importance. He knew that the resistance of the air acting on concave wings, or planes, at a small angle of incidence was resolved chiefly into lift, and he suspected that the amount of the lift was greater than the mathematical theory of hisday allowed. Above all, his treatise is stimulating, and suggests further inquiry and experiment along lines which have since proved to be the right lines.
Cayley's ideas were developed in practice by John Stringfellow, a manufacturer of lace machinery at Chard, in Somersetshire, and by his friend W. S. Henson, a young engineer. They constructed a light steam-engine, and designed an aeroplane, of which they entertained such high hopes that they took out a patent, and applied to Parliament for an Act to incorporate an Aerial Steam Transit Company. The reaction of public opinion on their proposals took the form of drag rather than lift, and they were thrown back on their own resources. In 1847 they made a model aeroplane, twenty feet in span, driven by two four-bladed airscrews, three feet in diameter, and they experimented with it on Bala Down, near Chard. It did not fly. Henson, completely discouraged, married and went to America; Stringfellow persisted, and in 1848 made a smaller model, ten feet in span, with airscrews sixteen inches in diameter. This machine, which had wings slightly cambered, with a rigid leading edge and a flexible trailing edge, made several successful flights, first in a long covered room at Chard, and later, before a number of witnesses, at Cremorne Gardens. After this success Stringfellow did no more for many years, until the foundation of the Aeronautical Society of Great Britain in 1866 roused him again to activity. At the society's exhibition of 1868, held in the Crystal Palace, he produced a model triplane, which ran along suspended from a wire, and, when its engine was in action, lifted itself as it ran.
The foundation of the Aeronautical Society, with the Duke of Argyll as president and with a council of men of science, attracted fresh minds to the study of flight, and gave the subject a respectable standing. Mr. Wenham's paper, read to the society on the27th of June 1866, proved that the effective sustaining area of a wing is limited to a narrow portion behind the leading edge; that, in order to increase this area, the planes of a flying machine might advantageously be placed one above another—an idea which was borrowed and put into practice by Mr. Stringfellow in his triplane—and that a heavy body, supported on planes, requires less power to drive it through the air at a high speed than to maintain it in flight at a low speed. For some years the society flourished; then its energies declined, and it fell into a state of suspended animation. At its second exhibition, in 1885, there were only sixteen exhibits as against seventy-eight at the exhibition of 1868. The prospects of practical success seemed remoter than ever. At last, thirty years after its foundation, it sprang into renewed activity, and, with Major B. F. S. Baden-Powell as secretary, did an immense work, from 1897 onwards, in directing and furthering the study of aviation. TheAeronautical Journal, which was published quarterly by the revived society, is a record of the years of progress and triumph.
The cause of this sudden revival is to be sought in the extraordinary fermentation which had been going on under the surface, both in Europe and America. The public was careless and sceptical; inventors who were seeking practical success were shy of premature publicity; papers read to learned societies were more concerned with theory than with practice; but there was hope in the air, and hundreds of minds were independently at work on the problem of flight. Some idea of the variety of suggestions and devices may be gathered from Mr. Octave Chanute'sProgress in Flying Machines, a reprint of a series of articles by him, which appeared, from 1891 onwards, inThe Railroad and Engineering Journalof New York City. It was said in the ancient world that there is nothing so absurdbut some philosopher has believed it; there is no imaginable way of flight that has not engaged the time and effort of some inventor. Yet among the multitude of attempts it is not difficult to trace the ancestry of the modern flying machine. Wing-flapping machines left no issue. Machines supported in the air by helicopters, that is, by horizontal revolving blades, can be made to rise from the ground, but cannot easily be made to travel. The way to success was by imitation of soaring birds; and it is worthy of note that some of the best minds were, from the first, fascinated by this method of flight, and were never tired of observing it. Cayley remarks that the swift, though it is a powerful flyer, is not able to elevate itself from level ground. Wenham records how an eagle, sitting in solitary state in the midst of the Egyptian plain, was fired at with a shotgun, and had to run full twenty yards, digging its talons into the soil, before it could raise itself into the air. M. Mouillard, of Cairo, spent more than thirty years in watching the flight of soaring birds, and devoted the whole of his book,L'Empire de l'Air(1881), to the investigation of soaring flight. The pelican, the turkey-buzzard, the vulture, the condor, have all had their students and disciples. M. Mouillard, indeed, maintains that if there be a moderate wind, a bird can remain a whole day soaring in the air, with no expenditure of power whatever. To those who have watched seagulls this may perhaps seem credible; but air is invisible, and soaring birds are skilful to choose a place, in the wake of a ship or in the neighbourhood of a cliff, where there is an up-current of air, so that when they glide by their own weight, though they are losing height in relation to the air, they are losing none in relation to the surface of the earth.
The parents of the modern flying machine were the gliders, that is, the men who launched themselves into the air on wings or planes of their own devising.The scientific investigators, who experimented with machines embodying the same principle, did much to assist the gliders, but in justice they must take a second place. The men who staked their lives were the men who, after many losses, were rewarded with the conquest of the air. There are stories of a certain Captain Lebris, how in 1854, near Douarnenez in Brittany, he constructed an artificial albatross, and tying it by a slip rope to a cart which was driven against the wind, mounted in it to a height of three hundred feet. But the first glider of whom we have any full knowledge is Otto Lilienthal of Berlin. He devoted his whole life to the study of aviation at a time when in Germany people looked upon such a pursuit as little better than lunacy. The principal professor of mathematics at the Berlin Gewerbe Academie, on hearing that Lilienthal was experimenting with aeronautics, advised him to spend no money on such things—a piece of advice which, Lilienthal remarks, was unhappily quite superfluous. In 1889 he completed, with the help of his brother, a series of experiments on the carrying capacity of arched, or cambered, wings, and published the results in a book entitledBird Flight as the Basis of Aviation. In his youth every crow that flew by presented him with a problem to solve in its slowly moving wings. Prolonged study led him to the conclusion that the slight fore-and-aft curvature of the wing was the secret of flying. But he knew too much to suppose that this conclusion solved the problem. A dozen other difficulties, including the difficulty of balance, remained to be mastered. When German societies for the advancement of aerial navigation began to be formed, he at first held aloof from them, for the balloon, which he regarded as the chief obstacle to the development of flight, monopolized their entire attention. His insistence on the cambered wing did not convince others, who went on experimenting withflat planes. German and Austrian aviators, it is true, were induced by his book to put aside flat surfaces and introduce arched wings. 'However,' he remarks, 'as this was done mainly on paper, in projects, and in aeronautical papers and discussions, I felt impelled myself to carry out my theory in practice.' So, in the summer of 1891, on a pair of bird-like wings, with eighty-six square feet of supporting surface, stabilized by a horizontal tail and a vertical fin aft, he began his gliding experiments. His whole apparatus, made of peeled willow sticks, covered with cotton shirting, weighed less than forty pounds. He was supported in it wholly on his forearms, which passed through padded tubes, while his hands grasped a cross-bar. He guided the machine and preserved its balance by shifting his weight, backwards or forwards or sideways. In this apparatus, altered and improved from time to time, Lilienthal, during the next five years, made more than two thousand successful glides. At first he used to jump off a spring-board; then he practised on some hills in the suburbs of Berlin; then, in the spring of 1894, he built a conical hill at Gross-Lichterfelde to serve him as a starting-ground. Later on, he moved to the Rhinow hills. His best glides were made against a light breeze at a gradient of about 1 in 10; and he could easily travel a hundred yards through the air. 'Regulating the centre of gravity', he says, 'becomes a second nature, like balancing on a bicycle; it is entirely a matter of practice and experience.' His most alarming experiences were from gusts of wind which would suddenly raise him many metres in the air and suspend him in a stationary position. But his skill was so great that he always succeeded in resuming his flight and alighting safely. He continued to improve and develop his machine. He made a double-surface glider, on the biplane principle, and flew on it. He experimentedwith engines, intended to flap the extremities of the wings—first a steam-engine of two horse-power, weighing forty-four pounds, then a simpler and lighter type, worked by compressed carbonic acid gas. But he explains that these can be safely introduced only if they do not impair the gliding efficiency of the machine, and he does not seem to have made much progress with them. His last improvement was a movable horizontal tail, or elevator, worked by a line attached to his head, to control the fore-and-aft balance of the machine. This fresh complexity was perhaps the cause of his death. On the 9th of August 1896 he started on a long glide from a hill about a hundred feet high; a sudden gust of wind caught him, and it is supposed that the involuntary movements of his head in the effort to regain his balance made matters worse; the machine plunged to the ground, and he was fatally injured.
Lilienthal was a good mathematician, a careful recorder of the results of his experiments, and a disinterested student of nature. Complete success was denied to him, but his work informed and stimulated others. The Wright brothers, when they first took up the problem of flight, had the advantage of acquaintance with Professor S. P. Langley's aeronautical researches, but their gliding experiments were shaped and inspired by what they had read of Lilienthal's achievements.
The other pioneer, who has earned a place beside Lilienthal, is Percy Pilcher. In 1893, at the age of twenty-seven, he became assistant lecturer in naval architecture and marine engineering at Glasgow University. He devoted all his spare time to aeronautics, and in 1895 built his first glider, which he named 'The Bat'. The machine was built, with the help of his sister, in the sitting-room of their lodging in Kersland street, Glasgow, and was tested on the banks of the Clyde, near Cardross. Some defects wererevealed by the tests; when these were remedied, and the glider was towed by a rope, Pilcher rose to a height of twenty feet, and remained in the air for nearly one minute. Thereafter he built, in rapid succession, three new gliders, all of different design, which he called 'The Beetle', 'The Gull', and 'The Hawk'. The professor of naval architecture at Glasgow, Sir John Biles, says of him, 'He was one of the few men I have met who had no sense of fear.... I was deterred from helping him as much as I ought to have done by a fear of the risks that he ran. He at one time talked to Lord Kelvin about helping him: Lord Kelvin spoke to me about it, and said that on no account would he help him, nor should I, as he would certainly break his neck. This was unfortunately too true a prophecy.' The Hawk was the best of his gliders; at Eynsford in Kent, on the 19th of June 1897, he made a perfectly balanced glide of 250 yards across a deep valley, towed only by a thin fishing line, 'which one could break with one's hands'. After this, Pilcher began to make plans for fitting an engine to his glider. Since the first appearance of the Otto engine in 1876, and of the Daimler engine eight years later, the oil-engine had steadily developed in lightness and power, but no engine exactly suitable for his purpose was on the market, so he resolved to build one. An engine of four horse-power, weighing forty pounds, with a wooden airscrew five feet in diameter, was, by his calculations, amply sufficient to maintain his glider in horizontal flight. The light engine has now been so enormously improved, that it comes near to developing one horse-power for every pound of weight. The violent have taken the kingdom of the air by force: in Pilcher's day the problem was more delicate. He worked at his engine in his leisure time, and, leaving the firm of Maxim & Nordenfeldt, by whom he had been employed from 1896 onwards, made, in 1898, his ownfirm of Wilson & Pilcher. In the spring of 1899 he was much impressed by Mr. Laurence Hargrave's soaring kites, exhibited by the inventor at a meeting of the Aeronautical Society, and it seems that he embodied some of Mr. Hargrave's ideas in his latest built machine, a triplane. He intended to fly this machine at Stanford Hall, Market Harborough, where he was staying with Lord Braye, but on the day appointed, the 30th of September 1899, the weather proved too wet. Nevertheless Pilcher consented to give some demonstrations on The Hawk, towed by a light line; during the second of these, while he was soaring at a height of thirty feet, one of the guy-wires of the tail broke, and the machine turned over and crashed. Pilcher never recovered consciousness, and died two days later. His name will always be remembered in the history of flight. If he had survived his risks for a year or two more, it seems not unlikely that he would have been the first man to navigate the air on a power-driven machine. He left behind him his gallant example, and some advances in design, for he improved the balance of the machine by raising its centre of gravity, and he provided it with wheels, fitted on shock-absorbers, for taking off and alighting.
Lilienthal and Pilcher are pre-eminent among the early gliders, for their efforts were scientific, continuous, and progressive. But there were others; and it is difficult, if not impossible, to determine the comparative value of experiments carried on, many of them in private, by inventors of all countries. Professor J. J. Montgomery, of California, carried out some successful glides, on machines of his own devising, as early as 1884; and Mr. Octave Chanute, the best historian of all these early efforts, having secured the services of Mr. A. M. Herring, a much younger man who had already learned to use a Lilienthal machine, made a series of experiments, with gliders of old and newtypes, on the shores of Lake Michigan, during the summer of 1896. About the same time some power-driven machines, attached to prepared tracks, were successfully flown. In 1893 Horatio Phillips flew a model, with many planes arranged one above another like a Venetian blind, on a circular track at Harrow; and in the same year Sir Hiram Maxim's large machine, with four thousand feet of supporting surface, was built at Baldwin's Park in Kent, and, when it was tested, developed so great a lift that it broke the guide rails placed to restrain it. Clement Ader, a French electrical engineer, worked at the problem of flight for many years, and, having obtained the support of the French Government, constructed a large bat-like machine, driven by a steam-engine of forty horse-power. In 1897 this machine was secretly tried, at the military camp of Satory, near Paris, and was reported on by a Government commission; all that was known thereafter was that the Government had refused to advance further funds, and that Ader had abandoned his attempts. When the Wrights had made their successful flights, a legend of earlier flights by Ader grew up in France; a heated controversy ensued, and the friends of M. Santos Dumont, who claimed that he was the first to fly over French soil, at length induced the French Government to publish the report on the trial of Ader's machine. The report proved that the machine had not left the ground.
It is not in mortals to command success; but those who study the record of the ingenious, persevering, and helpful work done for a quarter of a century by Mr. Laurence Hargrave, of Sydney, New South Wales, will agree with Mr. Chanute that this man deserved success. His earliest important paper was read to the Royal Society of New South Wales in 1884. In the course of the next ten years he made with his own hands eighteen different flying machines, of increasingsize, all of which flew. His earlier machines were not much larger than toys, and were supplied with power by the pull of stretched india-rubber. On this scale he was successful with a machine driven by an airscrew and with a machine driven by the flapping of wings. As his machines grew in size he turned his attention to engines. He was successful with compressed air; he made many experiments with explosion motors; and he succeeded in producing a steam-engine which weighed seven pounds and developed almost two-thirds of one horse-power. In 1893 he invented the box-kite, which is a true biplane, with the vertical sides of the kite doing the work of a stabilizing fin. This kite had a marked influence on the design of some early flying machines. He also invented the soaring kite. His hope that man would fly was more than hope; he refused to argue the question with objectors, for 'I know', he said, 'that success is dead sure to come'. Moreover he put all his researches at the disposal of others. He refused to take out any patents. He did all he could to induce workers to follow his example and communicate their ideas freely, so that progress might be quickened. His own ideas, his own inventions, and his own carefully recorded experiments were a solid step in that staircase of knowledge from which at last man launched himself into the air, and flew.
In America the pioneer who did most to further the science of human flight was Professor Samuel Pierpont Langley, of the Smithsonian Institute, in Washington. He was well known as an astronomer before ever he took up with aeronautics. From 1866 to 1887 he was professor of astronomy at the Western University of Pennsylvania, at Pittsburg. During his later years there he built a laboratory for aerial investigations, and carried out his famous experiments. His whirling table, with an arm about thirty feet long, which could be moved at all speeds up to seventy miles an hour,was devised to measure the lifting power of air resistance on brass plates suspended to the arm. In 1891 he published hisExperiments in Aerodynamics, which embodied the definite mathematical results obtained by years of careful research. It would be difficult to exaggerate the importance of this work. The law which governs the reaction of the air on planes travelling at various speeds and various angles of incidence had been guessed at, or seen in glimpses, by earlier investigators; but here were ascertained numerical values offered to students and inventors. The main result is best stated in Professor Langley's own words: 'When the arm was put in motion I found that the faster it went the less weight the plates registered on the scales, until at great speed they almost floated in the air.... I found that only one-twentieth of the force before supposed to be required to support bodies under such conditions was needed, and what before had seemed impossible began to look possible.... Some mathematicians, reasoning from false data, had concluded that if it took a certain amount of power to keep a thing from falling, it would take much additional power to make it advance. My experiment showed just the reverse ... that the faster the speed the less the force required to sustain the planes, and that it would cost less to transport such planes through the air at a high rate of speed than at a low one. I found further that one horse-power could carry brass plates weighing two hundred pounds at the rate of more than forty miles an hour in horizontal flight.'
When these researches were known and understood, their effect upon the practical handling of the problem of flight was immediate and decisive. The aeroplane, or gliding machine, had many rivals; they were all killed by Professor Langley's researches, which showed that the cheapest and best way to raise a plane in the air isto drive it forward at a small upward inclination; and that its weight can be best countered not by applying power to raise it vertically, but by driving it fast. In the statistical tables that he prepared he called the upward pressure of the airLift; the pressure which retards horizontal motion he calledDrift. The words make a happy pair, but the wordDriftis badly needed to describe the leeway of an aeroplane in a cross-wind, so that in England another pair of words,LiftandDrag, has been authoritatively substituted.
From this time onward Langley devoted himself to those other problems, especially the problems of balance, of mechanical power, and of safety in taking off and alighting, which had to be solved if he was to make a machine that should fly. He was much influenced, he says, by a mechanical toy, produced as early as 1871 by an ingenious Frenchman called Penaud, and named by its inventor the 'planophore'. This toy, which weighed only a little over half an ounce, was supported on wings, and was driven forward by an airscrew made of two feathers. The motive power was supplied by twisted strands of rubber which, as they untwisted, turned the airscrew. The wings were set at a dihedral angle, that is, they were bent upwards at the tips; and fore-and-aft stability was secured by a smaller pair of wings just in front of the airscrew. 'Simple as this toy looked,' says Professor Langley, 'it was the father of a future flying machine, and France ought to have the credit of it.' His own steam-driven flying machine was produced and successfully flown in 1896. It had two wings and a tail, with a supporting surface in all of seventy square feet; its total weight was seventy-two pounds; the engine, constructed by himself, weighed only seven pounds and developed one horse-power, which served to drive two airscrews, revolving in opposite directions. The best flight of this machine was more than three-quarters ofa mile, and was made over the Potomac river. When, on its first flight, it had flown for a minute, 'I felt', says Professor Langley, 'that something had been accomplished at last, for never in any part of the world or in any period had any machine of man's construction sustained itself in the air before for even half of this brief time'. His flying machines were called by Langley 'aerodromes', and the word 'aeroplane' was used by him, as it is used in theNew English Dictionaryof 1888, only in the sense of a single plane surface used for aerial experiments. But no usage, however authoritative, can withstand the tide of popular fashion; the machine is now an aeroplane, while aerodrome is the name given to the flying-ground from which it starts.
The success of his machine became widely known, and in 1898 the War Department of the United States, having ascertained that Langley was willing to devote all his spare time to the work, allotted fifty thousand dollars for the development, construction, and test of a large 'aerodrome', big enough to carry a man. The construction was long delayed by the difficulty of finding a suitable engine. This difficulty hampered all early attempts at flight. The internal-combustion engine was by this time pretty well understood, and, with the will to do it, might have been made light enough for the purpose. But it was almost an axiom with engineering firms that a very light engine could not wear well and was untrustworthy in other ways. One horse-power to the hundredweight was what they regarded as the standard of solid merit. Further, they were prejudiced against that extremely rapid movement of the parts which is necessary if the crank-shaft is to revolve more than a thousand times a minute. They were asked to depart from all their cherished canons and to risk failure and break-down in order that man should achieve what many of them regarded as animpossibility. It was with Langley as it was with Pilcher and the Wrights; he had to make his own engine. By 1901 he had completed with the aid of his assistants an engine of fifty-two horse-power, weighing, with all its appurtenances, less than five pounds to the horse-power. A year and a half more was spent in adapting and co-ordinating the frame and appliances, and in carrying out the shop tests. At last, on the 7th of October 1903, from a house-boat moored in the Potomac river, about forty miles below Washington, the first trial was made. The machine caught in the launching mechanism, and fell into the river, where it broke. It was repaired, and a second trial was made on the 8th of December 1903. Again the machine failed to clear the launching car, and plunged headlong into the river, where the frame was broken by zealous efforts to salve it in the dark. Nine days after this final failure the Wrights made their first successful power-driven flight, at Kitty Hawk, on the coast of North Carolina.
Langley was almost seventy years old when his last and most ambitious machine failed. He lived for two years more. If his contributions to the science of flight, which are his chief title to fame, were ruled out of the account, he would still be remembered as something more than a good astronomer—a man of many sciences, who cared little for his own advancement, and much for the advancement of knowledge.
From what has been said it is now possible to conceive how things stood when the brothers, Wilbur and Orville Wright, first attacked the problem of flying in the air. Men had flown, or rather had glided through the air, without engines to support and drive them. Machines had flown, without men to control and guide them. If the two achievements could be combined in one, the problem was solved; but the combination, besides bringing together both sets of difficulties anddangers, added new dangers and difficulties, greater than either. Plainly, there were two ways, and only two, of going about the business. Professor Langley held that in order to learn to fly, you must have a flying machine to begin with. Wilbur Wright, whose views on the point never varied from first to last, held that you must have a man to begin with. The brothers were impatient of 'the wasteful extravagance of mounting delicate and costly machinery on wings which no one knew how to manage'. When they began their experiments they had already reached the conclusion that the problem of constructing wings to carry the machine, and the problem of constructing a motor to drive it, presented no serious difficulty; but that the problem of equilibrium had been the real stumbling-block, and that this problem of equilibrium was the problem of flight itself. 'It seemed to us', says Wilbur Wright, 'that the main reason why the problem had remained so long unsolved was that no one had been able to obtain any adequate practice. We figured that Lilienthal in five years of time had spent only about five hours in actual gliding through the air. The wonder was not that he had done so little, but that he had accomplished so much. It would not be considered at all safe for a bicycle rider to attempt to ride through a crowded city street after only five hours' practice, spread out in bits of ten seconds each over a period of five years; yet Lilienthal with this brief practice was remarkably successful in meeting the fluctuations and eddies of wind gusts. We thought that if some method could be found by which it would be possible to practise by the hour instead of by the second there would be hope of advancing the solution of a very difficult problem.'
When this was written, in 1901, it was a forecast; it is now the history of a triumph. By prolongedscientific practice, undertaken with every possible regard to safety, on soaring and gliding machines, the Wrights became master pilots and conquerors of the air. Their success had in it no element of luck; it was earned, as an acrobat earns his skill. So confident did they become that to the end their machines were all machines of an unstable equilibrium, dependent for their safety on the skill and quickness of the pilot. Their triumph was a triumph of mind and character. Other men had more than their advantages, and failed, where these men succeeded. Great things have sometimes been done by a happy chance; it was not so with the Wrights. They planned great things, and measured themselves against them, and were equal to them.
Wilbur and Orville Wright were the sons of Milton Wright, of Dayton, Ohio. They came of New England stock. One of their ancestors emigrated from Essex in 1636, and settled at Springfield, Massachusetts; a later ancestor moved west, to Dayton. Wilbur was born in 1867, and Orville in 1871. They had two elder brothers and one younger sister; but Wilbur and Orville were so closely united in their lives and in their thoughts, that it is not easy to speak of them apart. Mr. Griffith Brewer, who knew them both, was often asked which of the two was the originator, and would reply, 'I think it was mostly Wilbur'; but would add, 'The thing could not have been done without Orville'. Wilbur, being four years the elder, no doubt took the lead; but all their ideas and experiments were shared, so that their very thought became a duet. Wilbur, who died in 1912, was a man of a steady mind and of a dominant character, hard-knit, quiet, intense. He has left some writings which reflect his nature; they have a certain grim humour, and they mean business; they push aside all irrelevance, and go straight to the point. After adventures in printing and journalism the two brothers set up at Dayton as cycle manufacturers.The death of Lilienthal, reported in the newspapers in 1896, first called their attention to flight, and they began to read all available books on the subject. They found that an immense amount of time and money had been spent on the problem of human flight—all to no effect. Makers of machines had abandoned their efforts. As for gliders, after the death of Lilienthal, Mr. Chanute had discontinued his experiments, and, a little later, Mr. Pilcher fell and was killed. When knowledge of these things came to the brothers, it appealed to them like a challenge. From 1899 onwards they turned all their thoughts to the problem. They watched the flight of birds to see if they could surprise the secret of balance. They studied gliding machines, and resolved to construct a machine of their own, more or less on the model of Mr. Chanute's most successful glider, which was a biplane, or 'double-decker'. When their machine was partly built, they wrote to the weather bureau at Washington, and learned that the strongest and most constant winds were to be found on the coast of North Carolina. They then wrote to the postmaster of Kitty Hawk, who testified that the sand-hills of that place were round and soft, well fitted for boys playing with flying machines. They took the parts of their machine to Kitty Hawk, assembled and completed it in a tent, and forthwith began their long years of continuous and progressive experiment. Their chief helper was Mr. Chanute. 'In the summer of 1901', they said, 'we became personally acquainted with Mr. Chanute. When he learned that we were interested in flying as a sport and not with any expectation of recovering the money we were expending on it, he gave us much encouragement. At our invitation he spent several weeks with us at our camp at Kill Devil Hill, four miles south of Kitty Hawk, during our experiments of that and the two succeeding years.'
The first two summers, 1900 and 1901, brought them some familiarity in the handling of their first two gliders, which they navigated lying face downward on the lower plane. In all their gliding experiments they studied safety first. They knew that the business they had embarked on was of necessity a long and dangerous one; that they were bound to encounter many dangers, and that each of them had only one life. They took no avoidable risks. Gliding seemed to them, at first, to have been discredited by the deaths of Lilienthal and Pilcher, so they planned to try their machine by tethering it with a rope and letting it float a few feet from the ground, while they practised manipulation. The wind proved to be not strong enough to sustain the weighted machine, and they were compelled to take to gliding. All their early glides were made as near the ground as possible. The machine had no vertical rudder, but they fitted it, in front, with what they called a horizontal rudder, that is, an elevator. By the use of this they could bring it to the ground at once when the wind was tricky and their balance was threatened. The lateral balance they attempted to control by warping the wings, but with no satisfactory results. They made glides longer than any on record, but while the problem of stability was still unsolved, there could be no real progress. At the end of 1901, Wilbur Wright made the prediction that men would some time fly, but that it would not be in their lifetime.
They returned to Dayton, and spent the winter in experiment and research. They had taken up aeronautics partly as a sport; they were now drawn deeper and deeper into the scientific study of it. They made a wind-tunnel, sixteen inches square and about six feet long, and tested in it the lift and drag of model wings, made in various sizes and with various aspect ratios. The tables which they compiled from theseexperiments were continually used by them thereafter, and superseded the tables of Lilienthal and Langley, which took no account of the aspect ratio. When they returned to Kitty Hawk, in the autumn of 1902, they took with them a greatly improved glider. The aspect ratio of the planes was six to one, instead of about three to one, as in their second glider. Further, while preserving the horizontal vane, or elevator, at the front of the machine, they added a vertical vane, or rudder, at the rear. It was their failure to control the lateral balance in the experiments of 1901 that suggested this device to them. From the first they had discarded the method, practised by Lilienthal and Pilcher, of adjusting the lateral balance by shifting the weight of the operator's body. This method seemed to them 'incapable of expansion to meet large conditions, because the weight to be moved and the distance of possible motion were limited, while the disturbing forces steadily increased, both with wing area and with wing velocity'. Accordingly they invented a method of warping the wings, to present them to the wind at different angles on the right and left sides. Thus the force of the wind was used to restore the balance which the wind itself had disturbed. But in their early gliders this warping process acted in an unexpected way. The wing which, in order to raise that side of the machine, was presented to the wind at the greater angle of incidence often proved to be the wing which lagged and sank. The decrease in speed, due to the extra drag, more than counterbalanced the effect of the larger angle. When they attempted to remedy this by introducing a fixed vertical vane in the rear, 'it increased the trouble and made the machine 'absolutely dangerous'. Any side-slip became irrecoverable by causing the vertical fixed vane to strike the wind on the side toward the low wing, instead of on the side toward the high wing, as it should have doneto correct the balance. 'It was some time', the brothers remark, 'before a remedy was discovered. This consisted of movable rudders working in conjunction with the twisting of the wings.' So that now three different parts of the machine had to be controlled by wires, worked swiftly and correctly by the operator, to preserve the balance. There were the wing tips which had to be warped. There was the horizontal vane in front which had to be adjusted, to keep the machine in level flight or to bring it to the ground. There was the vertical vane behind which had to be moved this way and that to secure the desired effect from the warping of the wings. 'For the sake of simplicity,' says Wilbur Wright, 'we decided to attach the wires controlling the vertical tail to the wires warping the wings, so that the operator, instead of having to control three things at once, would have to attend to only the forward horizontal rudder and the wing warping mechanism; and only the latter would be needed for controlling lateral balance.'
The thing was done. They had built an aeroplane that could fly; and the later introduction of an engine was as simple a matter as the harnessing of a horse to a carriage. 'With this apparatus', says Wilbur Wright, speaking of the glider of 1902, 'we made nearly seven hundred glides in the two or three weeks following. We flew it in calms and we flew it in winds as high as thirty-five miles an hour. We steered it to right and left, and performed all the evolutions necessary for flight. This was the first time in the history of the world that a movable vertical tail had been used in controlling the direction or the balance of a flying machine. It was also the first time that a movable vertical tail had been used, in combination with wings adjustable to different angles of incidence, in controlling the balance and direction of an aeroplane. We were the first to functionally employa movable vertical tail in a flying aeroplane. We were the first to employ wings adjustable to respectively different angles of incidence in a flying aeroplane. We were the first to use the two in combination in a flying aeroplane.'
It is a large claim, and every word of it is true. New inventions are commonly the work of many minds, and it would be easy to name at least half a dozen men to whose work the Wrights were indebted. But these were tributaries; the main achievement belongs wholly to the Wrights. Their quiet perseverance, through long years, in the face of every kind of difficulty, is only a part of their distinction; the alertness and humility of mind which refused all traffic with fixed ideas, and made dangers and disappointments the material of education, is what stamps them with greatness. They put themselves to school to the winds. They knew that there is no cheap or easy way to master nature, and that only the human spirit, at its best and highest, can win through in that long struggle. Their patience never failed. 'Skill', says Wilbur Wright, 'comes by the constant repetition of familiar feats rather than by a few overbold attempts at feats for which the performer is yet hardly prepared.' Man must learn to fly as he learns to walk. 'Before trying to rise to any dangerous height a man ought to know that in an emergency his mind and muscles will work by instinct rather than by conscious effort. There is no time to think.'
The machine of 1902, which might be called the victory machine, deserves a full description. It was a double-decked machine, with two planes fixed by struts one above the other about five feet apart. The planes were thirty-two feet in span, and five feet in chord. The total area of their supporting surfaces was about three hundred and five square feet. The operator lay on his face in the middle of the lowerplane. The horizontal rudder in front had a supporting surface of fifteen square feet. The vertical tail, as they called it, which was the true rudder, was reduced after trial to six square feet. The machine was supported on the ground by skids, and was very strongly built. It weighed a hundred and sixteen and a half pounds, to which must be added about a hundred and forty pounds for the weight of the operator. It performed about a thousand glides, with only one injury, though it made many hard landings at full speed on uneven ground. The longest glide was 622-1/2 feet, traversed in twenty-six seconds. The glides were made from the Kill Devil sand-hills, near Kitty Hawk—mounds of sand heaped up by the wind, the biggest having a height of a hundred feet.
The time had now come to invite an engine to bear a part in the proceedings. In the autumn of 1903 the brothers returned to Kitty Hawk for their fourth season of experiment. They had built in the winter a machine weighing six hundred pounds, including the operator and an eight horse-power motor. Finding that the motor gave more power than had been estimated, they added a hundred and fifty pounds of weight in strengthening the wings and other parts. The airscrews, built from their own calculations, gave in useful work two-thirds of the power expended. Before trying this machine, however, they continued their practice with the old glider, and made a number of flights in which they remained in the air for over a minute, often soaring for a considerable time in one spot, without any descent at all.
It was late in the season, the 17th of December 1903, when they first tried the power machine. A general invitation to be present at the trial had been given to the people living within five or six miles, but 'not many were willing to face the rigours of a cold December wind in order to see, as they no doubtthought, another flying machinenotfly'. Five persons besides the brothers were present. Mr. Orville Wright's narrative, written for the Aeronautical Society of Great Britain, must be given in his own words:
'On the morning of December 17th, between the hours of 10.30 o'clock and noon, four flights were made, two by Mr. Orville Wright, and two by Mr. Wilbur Wright. The starts were all made from a point on the levels, and about 200 feet west of our camp, which is located about a quarter of a mile north of the Kill Devil Sand Hill, in Dare County, North Carolina. The wind at the time of the flights had a velocity of twenty-seven miles an hour at 10 o'clock, and 24 miles an hour at noon, as recorded by the anemometer at the Kitty Hawk weather bureau station. This anemometer is 30 feet from the ground. Our own measurements, made with a hand-anemometer at a height of four feet from the ground, showed a velocity of about 22 miles when the first flight was made, and 20-1/2 miles at the time of the last one. The flights were directly against the wind. Each time the machine started from the level ground by its own power alone, with no assistance from gravity or any other sources whatever. After a run of about 40 feet along a mono-rail track, which held the machine eight inches from the ground, it rose from the track and, under the direction of the operator, climbed upward on an inclined course till a height of 8 or 10 feet from the ground was reached, after which the course was kept as near horizontal as the wind gusts and the limited skill of the operator would permit. Into the teeth of a December gale the Flyer made its way forward with a speed of 10 miles an hour over the ground, and 30 to 35 miles an hour through the air. It had previously been decided that, for reasons of personal safety, these first trialsshould be made as close to the ground as possible. The height chosen was scarcely sufficient for manœuvring in so gusty a wind and with no previous acquaintance with the conduct of the machine and its controlling mechanisms. Consequently the first flight was short. The succeeding flights rapidly increased in length and at the fourth trial a flight of 59 seconds was made, in which time the machine flew a little more than a half-mile through the air and a distance of 852 feet over the ground. The landing was due to a slight error of judgement on the part of the operator. After passing over a little hummock of sand, in attempting to bring the machine down to the desired height the operator turned the rudder too far, and the machine turned downward more quickly than had been expected. The reverse movement of the rudder was a fraction of a second too late to prevent the machine from touching the ground and thus ending the flight. The whole occurrence occupied little, if any, more than one second of time.