Chapter VI: Part I: The Evolution of the Aeroplane (5)

Maxim's intention was, before attempting free flight, to get as much data as possible regarding the conditions under which flight must be obtained, by what is known in these days as 'taxi-ing'--that is, running the propellers at sufficient speed to drive the machine along the ground without actually mounting into the air. He knew that he had an immense lifting surface and a tremendous amount of power in his engine even when the total weight of the experimental plant was taken into consideration, and thus he set about to devise some means of keeping the machine on the nine foot gauge rail track which had been constructed for the trials. At the outset he had a set of very heavy cast-iron wheels made on which to mount the machine, the total weight of wheels, axles, and connections being about one and a half tons. These were so constructed that the light flanged wheels which supported the machine on the steel rails could be lifted six inches above the track, still leaving the heavy wheels on the rails for guidance of the machine. 'This arrangement,' Maxim states, 'was tried on several occasions, the machine being run fast enough to lift the forward end off the track. However, I found considerable difficulty in starting and stopping quickly on account of the great weight, and the amount of energy necessary to set such heavy wheels spinning at a high velocity. The last experiment with these wheels was made when a head wind was blowing at the rate of about ten miles an hour. It was rather unsteady, and when the machine was running at its greatest velocity, a sudden gust lifted not only the front end, but also the heavy front wheels completely off the track, and the machine falling on soft ground was soon blown over by the wind.'

Consequently, a safety track was provided, consisting of squared pine logs, three inches by nine inches, placed about two feet above the steel way and having a thirty-foot gauge. Four extra wheels were fitted to the machine on outriggers and so adjusted that, if the machine should lift one inch clear of the steel rails, the wheels at the ends of the outriggers would engage the under side of the pine trackway.

The first fully loaded run was made in a dead calm with 150 lbs. steam pressure to the square inch, and there was no sign of the wheels leaving the steel track. On a second run, with 230 lbs. steam pressure the machine seemed to alternate between adherence to the lower and upper tracks, as many as three of the outrigger wheels engaging at the same time, and the weight on the steel rails being reduced practically to nothing. In preparation for a third run, in which it was intended to use full power, a dynamometer was attached to the machine and the engines were started at 200 lbs. pressure, which was gradually increased to 310 lbs per square inch. The incline of the track, added to the reading of the dynamometer, showed a total screw thrust of 2,164 lbs. After the dynamometer test had been completed, and everything had been made ready for trial in motion, careful observers were stationed on each side of the track, and the order was given to release the machine. What follows is best told in Maxim's own words:--

'The enormous screw-thrust started the engine so quickly that it nearly threw the engineers off their feet, and the machine bounded over the track at a great rate. Upon noticing a slight diminution in the steam pressure, I turned on more gas, when almost instantly the steam commenced to blow a steady blast from the small safety valve, showing that the pressure was at least 320 lbs. in the pipes supplying the engines with steam. Before starting on this run, the wheels that were to engage the upper track were painted, and it was the duty of one of my assistants to observe these wheels during the run, while another assistant watched the pressure gauges and dynagraphs. The first part of the track was up a slight incline, but the machine was lifted clear of the lower rails and all of the top wheels were fully engaged on the upper track when about 600 feet had been covered. The speed rapidly increased, and when 900 feet had been covered, one of the rear axle trees, which were of two-inch steel tubing, doubled up and set the rear end of the machine completely free. The pencils ran completely across the cylinders of the dynagraphs and caught on the underneath end. The rear end of the machine being set free, raised considerably above the track and swayed. At about 1,000 feet, the left forward wheel also got clear of the upper track, and shortly afterwards the right forward wheel tore up about 100 feet of the upper track. Steam was at once shut off and the machine sank directly to the earth, embedding the wheels in the soft turf without leaving any other marks, showing most conclusively that the machine was completely suspended in the air before it settled to the earth. In this accident, one of the pine timbers forming the upper track went completely through the lower framework of the machine and broke a number of the tubes, but no damage was done to the machinery except a slight injury to one of the screws.'

It is a pity that the multifarious directions in which Maxim turned his energies did not include further development of the aeroplane, for it seems fairly certain that he was as near solution of the problem as Ader himself, and, but for the holding-down outer track, which was really the cause of his accident, his machine would certainly have achieved free flight, though whether it would have risen, flown and alighted, without accident, is matter for conjecture.

The difference between experiments with models and with full-sized machines is emphasised by Maxim's statement to the effect that with a small apparatus for ascertaining the power required for artificial flight, an angle of incidence of one in fourteen was most advantageous, while with a large machine he found it best to increase his angle to one in eight in order to get the maximum lifting effect on a short run at a moderate speed. He computed the total lifting effect in the experiments which led to the accident as not less than 10,000 lbs., in which is proof that only his rail system prevented free flight.

X. SAMUEL PIERPOINT LANGLEY

Langley was an old man when he began the study of aeronautics, or, as he himself might have expressed it, the study of aerodromics, since he persisted in calling the series of machines he built 'Aerodromes,' a word now used only to denote areas devoted to use as landing spaces for flying machines; the Wright Brothers, on the other hand, had the great gift of youth to aid them in their work. Even so it was a great race between Langley, aided by Charles Manly, and Wilbur and Orville Wright, and only the persistent ill-luck which dogged Langley from the start to the finish of his experiments gave victory to his rivals. It has been proved conclusively in these later years of accomplished flight that the machine which Langley launched on the Potomac River in October of 1903 was fully capable of sustained flight, and only the accidents incurred in launching prevented its pilot from being the first man to navigate the air successfully in a power-driven machine.

The best account of Langley's work is that diffused throughout a weighty tome issued by the Smithsonian Institution, entitled the Langley Memoir on Mechanical Flight, of which about one-third was written by Langley himself, the remainder being compiled by Charles M. Manly, the engineer responsible for the construction of the first radial aero-engine, and chief assistant to Langley in his experiments. To give a twentieth of the contents of this volume in the present short account of the development of mechanical flight would far exceed the amount of space that can be devoted even to so eminent a man in aeronautics as S. P. Langley, who, apart from his achievement in the construction of a power-driven aeroplane really capable of flight, was a scientist of no mean order, and who brought to the study of aeronautics the skill of the trained investigator allied to the inventive resource of the genius.

That genius exemplified the antique saw regarding the infinite capacity for taking pains, for the Langley Memoir shows that as early as 1891 Langley had completed a set of experiments, lasting through years, which proved it possible to construct machines giving such a velocity to inclined surfaces that bodies indefinitely heavier than air could be sustained upon it and propelled through it at high speed. For full account (very full) of these experiments, and of a later series leading up to the construction of a series of 'model aerodromes' capable of flight under power, it is necessary to turn to the bulky memoir of Smithsonian origin.

The account of these experiments as given by Langley himself reveals the humility of the true investigator. Concerning them, Langley remarks that, 'Everything here has been done with a view to putting a trial aerodrome successfully in flight within a few years, and thus giving an early demonstration of the only kind which is conclusive in the eyes of the scientific man, as well as of the general public--a demonstration that mechanical flight is possible--by actually flying. All that has been done has been with an eye principally to this immediate result, and all the experiments given in this book are to be considered only as approximations to exact truth. All were made with a view, not to some remote future, but to an arrival within the compass of a few years at some result in actual flight that could not be gainsaid or mistaken.'

With a series of over thirty rubber-driven models Langley demonstrated the practicability of opposing curved surfaces to the resistance of the air in such a way as to achieve flight, in the early nineties of last century; he then set about finding the motive power which should permit of the construction of larger machines, up to man-carrying size. The internal combustion engine was then an unknown quantity, and he had to turn to steam, finally, as the propulsive energy for his power plant. The chief problem which faced him was that of the relative weight and power of his engine; he harked back to the Stringfellow engine of 1868, which in 1889 came into the possession of the Smithsonian Institution as a historical curiosity. Rightly or wrongly Langley concluded on examination that this engine never had developed and never could develop more than a tenth of the power attributed to it; consequently he abandoned the idea of copying the Stringfellow design and set about making his own engine.

How he overcame the various difficulties that faced him and constructed a steam-engine capable of the task allotted to it forms a story in itself, too long for recital here. His first power-driven aerodrome of model size was begun in November of 1891, the scale of construction being decided with the idea that it should be large enough to carry an automatic steering apparatus which would render the machine capable of maintaining a long and steady flight. The actual weight of the first model far exceeded the theoretical estimate, and Langley found that a constant increase of weight under the exigencies of construction was a feature which could never be altogether eliminated. The machine was made principally of steel, the sustaining surfaces being composed of silk stretched from a steel tube with wooden attachments. The first engines were the oscillating type, but were found deficient in power. This led to the construction of single-acting inverted oscillating engines with high and low pressure cylinders, and with admission and exhaust ports to avoid the complication and weight of eccentric and valves. Boiler and furnace had to be specially designed; an analysis of sustaining surfaces and the settlement of equilibrium while in flight had to be overcome, and then it was possible to set about the construction of the series of model aerodromes and make test of their 'lift.'

By the time Langley had advanced sufficiently far to consider it possible to conduct experiments in the open air, even with these models, he had got to his fifth aerodrome, and to the year 1894. Certain tests resulted in failure, which in turn resulted in further modifications of design, mainly of the engines. By February of 1895 Langley reported that under favourable conditions a lift of nearly sixty per cent of the flying weight was secured, but although this was much more than was required for flight, it was decided to postpone trials until two machines were ready for the test. May, 1896, came before actual trials were made, when one machine proved successful and another, a later design, failed. The difficulty with these models was that of securing a correct angle for launching; Langley records how, on launching one machine, it rose so rapidly that it attained an angle of sixty degrees and then did a tail slide into the water with its engines working at full speed, after advancing nearly forty feet and remaining in the air for about three seconds. Here, Langley found that he had to obtain greater rigidity in his wings, owing to the distortion of the form of wing under pressure, and how he overcame this difficulty constitutes yet another story too long for the telling here.

Field trials were first attempted in 1893, and Langley blamed his launching apparatus for their total failure. There was a brief, but at the same time practical, success in model flight in 1894, extending to between six and seven seconds, but this only proved the need for strengthening of the wing. In 1895 there was practically no advance toward the solution of the problem, but the flights of May 6th and November 28th, 1896, were notably successful. A diagram given in Langley's memoir shows the track covered by the aerodrome on these two flights; in the first of them the machine made three complete circles, covering a distance of 3,200 feet; in the second, that of November 28th, the distance covered was 4,200 feet, or about three-quarters of a mile, at a speed of about thirty miles an hour.

These achievements meant a good deal; they proved mechanically propelled flight possible. The difference between them and such experiments as were conducted by Clement Ader, Maxim, and others, lay principally in the fact that these latter either did or did not succeed in rising into the air once, and then, either willingly or by compulsion, gave up the quest, while Langley repeated his experiments and thus attained to actual proof of the possibilities of flight. Like these others, however, he decided in 1896 that he would not undertake the construction of a large man-carrying machine. In addition to a multitude of actual duties, which left him practically no time available for original research, he had as an adverse factor fully ten years of disheartening difficulties in connection with his model machines. It was President McKinley who, by requesting Langley to undertake the construction and test of a machine which might finally lead to the development of a flying machine capable of being used in warfare, egged him on to his final experiment. Langley's acceptance of the offer to construct such a machine is contained in a letter addressed from the Smithsonian Institution on December 12th, 1898, to the Board of Ordnance and Fortification of the United States War Department; this letter is of such interest as to render it worthy of reproduction:--

'Gentlemen,--In response to your invitation I repeat what I had the honour to say to the Board--that I am willing, with the consent of the Regents of this Institution, to undertake for the Government the further investigation of the subject of the construction of a flying machine on a scale capable of carrying a man, the investigation to include the construction, development and test of such a machine under conditions left as far as practicable in my discretion, it being understood that my services are given to the Government in such time as may not be occupied by the business of the Institution, and without charge.

'I have reason to believe that the cost of the construction will come within the sum of $50,000.00, and that not more than one-half of that will be called for in the coming year.

'I entirely agree with what I understand to be the wish of the Board that privacy be observed with regard to the work, and only when it reaches a successful completion shall I wish to make public the fact of its success.

'I attach to this a memorandum of my understanding of some points of detail in order to be sure that it is also the understanding of the Board, and I am, gentlemen, with much respect, your obedient servant, S. P. Langley.'

One of the chief problems in connection with the construction of a full-sized apparatus was that of the construction of an engine, for it was realised from the first that a steam power plant for a full-sized machine could only be constructed in such a way as to make it a constant menace to the machine which it was to propel. By this time (1898) the internal combustion engine had so far advanced as to convince Langley that it formed the best power plant available. A contract was made for the delivery of a twelve horse-power engine to weigh not more than a hundred pounds, but this contract was never completed, and it fell to Charles M. Manly to design the five-cylinder radial engine, of which a brief account is included in the section of this work devoted to aero engines, as the power plant for the Langley machine.

The history of the years 1899 to 1903 in the Langley series of experiments contains a multitude of detail far beyond the scope of this present study, and of interest mainly to the designer. There were frames, engines, and propellers, to be considered, worked out, and constructed. We are concerned here mainly with the completed machine and its trials. Of these latter it must be remarked that the only two actual field trials which took place resulted in accidents due to the failure of the launching apparatus, and not due to any inherent defect in the machine. It was intended that these two trials should be the first of a series, but the unfortunate accidents, and the fact that no further funds were forthcoming for continuance of experiments, prevented Langley's success, which, had he been free to go through as he intended with his work, would have been certain.

The best brief description of the Langley aerodrome in its final form, and of the two attempted trials, is contained in the official report of Major M. M. Macomb of the United States Artillery Corps, which report is here given in full:--

REPORT

Experiments with working models which were concluded August 8 last having proved the principles and calculations on which the design of the Langley aerodrome was based to be correct, the next step was to apply these principles to the construction of a machine of sufficient size and power to permit the carrying of a man, who could control the motive power and guide its flight, thus pointing the way to attaining the final goal of producing a machine capable of such extensive and precise aerial flight, under normal atmospheric conditions, as to prove of military or commercial utility.

Mr C. M. Manly, working under Professor Langley, had, by the summer of 1903, succeeded in completing an engine-driven machine which under favourable atmospheric conditions was expected to carry a man for any time up to half an hour, and to be capable of having its flight directed and controlled by him.

The supporting surface of the wings was ample, and experiment showed the engine capable of supplying more than the necessary motive power.

Owing to the necessity of lightness, the weight of the various elements had to be kept at a minimum, and the factor of safety in construction was therefore exceedingly small, so that the machine as a whole was delicate and frail and incapable of sustaining any unusual strain. This defect was to be corrected in later models by utilising data gathered in future experiments under varied conditions.

One of the most remarkable results attained was the production of a gasoline engine furnishing over fifty continuous horse-power for a weight of 120 lbs.

The aerodrome, as completed and prepared for test, is briefly described by Professor Langley as 'built of steel, weighing complete about 730 lbs., supported by 1,040 feet of sustaining surface, having two propellers driven by a gas engine developing continuously over fifty brake horse-power.'

The appearance of the machine prepared for flight was exceedingly light and graceful, giving an impression to all observers of being capable of successful flight.

On October 7 last everything was in readiness, and I witnessed the attempted trial on that day at Widewater, Va. On the Potomac. The engine worked well and the machine was launched at about 12.15 p.m. The trial was unsuccessful because the front guy-post caught in its support on the launching car and was not released in time to give free flight, as was intended, but, on the contrary, caused the front of the machine to be dragged downward, bending the guy-post and making the machine plunge into the water about fifty yards in front of the house-boat. The machine was subsequently recovered and brought back to the house-boat. The engine was uninjured and the frame only slightly damaged, but the four wings and rudder were practically destroyed by the first plunge and subsequent towing back to the house-boat.

This accident necessitated the removal of the house-boat to Washington for the more convenient repair of damages.

On December 8 last, between 4 and 5 p.m., another attempt at a trial was made, this time at the junction of the Anacostia with the Potomac, just below Washington Barracks.

On this occasion General Randolph and myself represented the Board of Ordnance and Fortification. The launching car was released at 4.45 p.m. being pointed up the Anacostia towards the Navy Yard. My position was on the tug Bartholdi, about 150 feet from and at right angles to the direction of proposed flight. The car was set in motion and the propellers revolved rapidly, the engine working perfectly, but there was something wrong with the launching. The rear guy-post seemed to drag, bringing the rudder down on the launching ways, and a crashing, rending sound, followed by the collapse of the rear wings, showed that the machine had been wrecked in the launching, just how, it was impossible for me to see. The fact remains that the rear wings and rudder were wrecked before the machine was free of the ways. Their collapse deprived the machine of its support in the rear, and it consequently reared up in front under the action of the motor, assumed a vertical position, and then toppled over to the rear, falling into the water a few feet in front of the boat.

Mr Manly was pulled out of the wreck uninjured and the wrecked machine--was subsequently placed upon the house-boat, and the whole brought back to Washington.

From what has been said it will be seen that these unfortunate accidents have prevented any test of the apparatus in free flight, and the claim that an engine-driven, man-carrying aerodrome has been constructed lacks the proof which actual flight alone can give.

Having reached the present stage of advancement in its development, it would seem highly desirable, before laying down the investigation, to obtain conclusive proof of the possibility of free flight, not only because there are excellent reasons to hope for success, but because it marks the end of a definite step toward the attainment of the final goal.

Just what further procedure is necessary to secure successful flight with the large aerodrome has not yet been decided upon. Professor Langley is understood to have this subject under advisement, and will doubtless inform the Board of his final conclusions as soon as practicable.

In the meantime, to avoid any possible misunderstanding, it should be stated that even after a successful test of the present great aerodrome, designed to carry a man, we are still far from the ultimate goal, and it would seem as if years of constant work and study by experts, together with the expenditure of thousands of dollars, would still be necessary before we can hope to produce an apparatus of practical utility on these lines.--Washington, January 6, 1904.

A subsequent report of the Board of ordnance and Fortification to the Secretary of War embodied the principal points in Major Macomb's report, but as early as March 3rd, 1904, the Board came to a similar conclusion to that of the French Ministry of War in respect of Clement Ader's work, stating that it was not 'prepared to make an additional allotment at this time for continuing the work.' This decision was in no small measure due to hostile newspaper criticisms. Langley, in a letter to the press explaining his attitude, stated that he did not wish to make public the results of his work till these were certain, in consequence of which he refused admittance to newspaper representatives, and this attitude produced a hostility which had effect on the United States Congress. An offer was made to commercialise the invention, but Langley steadfastly refused it. Concerning this, Manly remarks that Langley had 'given his time and his best labours to the world without hope of remuneration, and he could not bring himself, at his stage of life, to consent to capitalise his scientific work.'

The final trial of the Langley aerodrome was made on December 8th, 1903; nine days later, on December 17th, the Wright Brothers made their first flight in a power-propelled machine, and the conquest of the air was thus achieved. But for the two accidents that spoilt his trials, the honour which fell to the Wright Brothers would, beyond doubt, have been secured by Samuel Pierpoint Langley.

XI. THE WRIGHT BROTHERS

Such information as is given here concerning the Wright Brothers is derived from the two best sources available, namely, the writings of Wilbur Wright himself, and a lecture given by Dr Griffith Brewer to members of the Royal Aeronautical Society. There is no doubt that so far as actual work in connection with aviation accomplished by the two brothers is concerned, Wilbur Wright's own statements are the clearest and best available. Apparently Wilbur was, from the beginning, the historian of the pair, though he himself would have been the last to attempt to detract in any way from the fame that his brother's work also deserves. Throughout all their experiments the two were inseparable, and their work is one indivisible whole; in fact, in every department of that work, it is impossible to say where Orville leaves off and where Wilbur begins.

It is a great story, this of the Wright Brothers, and one worth all the detail that can be spared it. It begins on the 16th April, 1867, when Wilbur Wright was born within eight miles of Newcastle, Indiana. Before Orville's birth on the 19th August, 1871, the Wright family had moved to Dayton, Ohio, and settled on what is known as the 'West Side' of the town. Here the brothers grew up, and, when Orville was still a boy in his teens, he started a printing business, which, as Griffith Brewer remarks, was only limited by the smallness of his machine and small quantity of type at his disposal. This machine was in such a state that pieces of string and wood were incorporated in it by way of repair, but on it Orville managed to print a boys' paper which gained considerable popularity in Dayton 'West Side.' Later, at the age of seventeen, he obtained a more efficient outfit, with which he launched a weekly newspaper, four pages in size, entitled The West Side News. After three months' running the paper was increased in size and Wilbur came into the enterprise as editor, Orville remaining publisher. In 1894 the two brothers began the publication of a weekly magazine, Snap-Shots, to which Wilbur contributed a series of articles on local affairs that gave evidence of the incisive and often sarcastic manner in which he was able to express himself throughout his life. Dr Griffith Brewer describes him as a fearless critic, who wrote on matters of local interest in a kindly but vigorous manner, which did much to maintain the healthy public municipal life of Dayton.

Editorial and publishing enterprise was succeeded by the formation, just across the road from the printing works, of the Wright Cycle Company, where the two brothers launched out as cycle manufacturers with the 'Van Cleve' bicycle, a machine of great local repute for excellence of construction, and one which won for itself a reputation that lasted long after it had ceased to be manufactured. The name of the machine was that of an ancestor of the brothers, Catherine Van Cleve, who was one of the first settlers at Dayton, landing there from the River Miami on April 1st, 1796, when the country was virgin forest.

It was not until 1896 that the mechanical genius which characterised the two brothers was turned to the consideration of aeronautics. In that year they took up the problem thoroughly, studying all the aeronautical information then in print. Lilienthal's writings formed one basis for their studies, and the work of Langley assisted in establishing in them a confidence in the possibility of a solution to the problems of mechanical flight. In 1909, at the banquet given by the Royal Aero Club to the Wright Brothers on their return to America, after the series of demonstration flights carried out by Wilbur Wright on the Continent, Wilbur paid tribute to the great pioneer work of Stringfellow, whose studies and achievements influenced his own and Orville's early work. He pointed out how Stringfellow devised an aeroplane having two propellers and vertical and horizontal steering, and gave due place to this early pioneer of mechanical flight.

Neither of the brothers was content with mere study of the work of others. They collected all the theory available in the books published up to that time, and then built man-carrying gliders with which to test the data of Lilienthal and such other authorities as they had consulted. For two years they conducted outdoor experiments in order to test the truth or otherwise of what were enunciated as the principles of flight; after this they turned to laboratory experiments, constructing a wind tunnel in which they made thousands of tests with models of various forms of curved planes. From their experiments they tabulated thousands of readings, which Griffith Brewer remarks as giving results equally efficient with those of the elaborate tables prepared by learned institutions.

Wilbur Wright has set down the beginnings of the practical experiments made by the two brothers very clearly. 'The difficulties,' he says, 'which obstruct the pathway to success in flying machine construction are of three general classes: (1) Those which relate to the construction of the sustaining wings; (2) those which relate to the generation and application of the power required to drive the machine through the air; (3) those relating to the balancing and steering of the machine after it is actually in flight. Of these difficulties two are already to a certain extent solved. Men already know how to construct wings, or aeroplanes, which, when driven through the air at sufficient speed, will not only sustain the weight of the wings themselves, but also that of the engine and the engineer as well. Men also know how to build engines and' screws of sufficient lightness and power to drive these planes at sustaining speed. Inability to balance and steer still confronts students of the flying problem, although nearly ten years have passed (since Lilienthal's success). When this one feature has been worked out, the age of flying machines will have arrived, for all other difficulties are of minor importance.

'The person who merely watches the flight of a bird gathers the impression that the bird has nothing to think of but the flapping of its wings. As a matter of fact, this is a very small part of its mental labour. Even to mention all the things the bird must constantly keep in mind in order to fly securely through the air would take a considerable time. If I take a piece of paper and, after placing it parallel with the ground, quickly let it fall, it will not settle steadily down as a staid, sensible piece of paper ought to do, but it insists on contravening every recognised rule of decorum, turning over and darting hither and thither in the most erratic manner, much after the style of an untrained horse. Yet this is the style of steed that men must learn to manage before flying can become an everyday sport. The bird has learned this art of equilibrium, and learned it so thoroughly that its skill is not apparent to our sight. We only learn to appreciate it when we can imitate it.

'Now, there are only two ways of learning to ride a fractious horse: one is to get on him and learn by actual practice how each motion and trick may be best met; the other is to sit on a fence and watch the beast awhile, and then retire to the house and at leisure figure out the best way of overcoming his jumps and kicks. The latter system is the safer, but the former, on the whole, turns out the larger proportion of good riders. It is very much the same in learning to ride a flying machine; if you are looking for perfect safety you will do well to sit on a fence and watch the birds, but if you really wish to learn you must mount a machine and become acquainted with its tricks by actual trial. The balancing of a gliding or flying machine is very simple in theory. It merely consists in causing the centre of pressure to coincide with the centre of gravity.'

These comments are taken from a lecture delivered by Wilbur Wright before the Western Society of Engineers in September of 1901, under the presidency of Octave Chanute. In that lecture Wilbur detailed the way in which he and his brother came to interest themselves in aeronautical problems and constructed their first glider. He speaks of his own notice of the death of Lilienthal in 1896, and of the way in which this fatality roused him to an active interest in aeronautical problems, which was stimulated by reading Professor Marey's Animal Mechanism, not for the first time. 'From this I was led to read more modern works, and as my brother soon became equally interested with myself, we soon passed from the reading to the thinking, and finally to the working stage. It seemed to us 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 practice by the hour instead of by the second there would be hope of advancing the solution of a very difficult problem. It seemed feasible to do this by building a machine which would be sustained at a speed of eighteen miles per hour, and then finding a locality where winds of this velocity were common. With these conditions a rope attached to the machine to keep it from floating backward would answer very nearly the same purpose as a propeller driven by a motor, and it would be possible to practice by the hour, and without any serious danger, as it would not be necessary to rise far from the ground, and the machine would not have any forward motion at all. We found, according to the accepted tables of air pressure on curved surfaces, that a machine spreading 200 square feet of wing surface would be sufficient for our purpose, and that places would easily be found along the Atlantic coast where winds of sixteen to twenty-five miles were not at all uncommon. When the winds were low it was our plan to glide from the tops of sandhills, and when they were sufficiently strong to use a rope for our motor and fly over one spot. Our next work was to draw up the plans for a suitable machine. After much study we finally concluded that tails were a source of trouble rather than of assistance, and therefore we decided to dispense with them altogether. It seemed reasonable that if the body of the operator could be placed in a horizontal position instead of the upright, as in the machines of Lilienthal, Pilcher, and Chanute, the wind resistance could be very materially reduced, since only one square foot instead of five would be exposed. As a full half horse-power would be saved by this change, we arranged to try at least the horizontal position. Then the method of control used by Lilienthal, which consisted in shifting the body, did not seem quite as quick or effective as the case required; so, after long study, we contrived a system consisting of two large surfaces on the Chanute double-deck plan, and a smaller surface placed a short distance in front of the main surfaces in such a position that the action of the wind upon it would counterbalance the effect of the travel of the centre of pressure on the main surfaces. Thus changes in the direction and velocity of the wind would have little disturbing effect, and the operator would be required to attend only to the steering of the machine, which was to be effected by curving the forward surface up or down. The lateral equilibrium and the steering to right or left was to be attained by a peculiar torsion of the main surfaces which was equivalent to presenting one end of the wings at a greater angle than the other. In the main frame a few changes were also made in the details of construction and trussing employed by Mr Chanute. The most important of these were: (1) The moving of the forward main crosspiece of the frame to the extreme front edge; (2) the encasing in the cloth of all crosspieces and ribs of the surfaces; (3) a rearrangement of the wires used in trussing the two surfaces together, which rendered it possible to tighten all the wires by simply shortening two of them.'

The brothers intended originally to get 200 square feet of supporting surface for their glider, but the impossibility of obtaining suitable material compelled them to reduce the area to 165 square feet, which, by the Lilienthal tables, admitted of support in a wind of about twenty-one miles an hour at an angle of three degrees. With this glider they went in the summer of I 1900 to the little settlement of Kitty Hawk, North Carolina, situated on the strip of land dividing Albemarle Sound from the Atlantic. Here they reckoned on obtaining steady wind, and here, on the day that they completed the machine, they took it out for trial as a kite with the wind blowing at between twenty-five and thirty miles an hour. They found that in order to support a man on it the glider required an angle nearer twenty degrees than three, and even with the wind at thirty miles an hour they could not get down to the planned angle of three degrees. 'Later, when the wind was too light to support the machine with a man on it, they tested it as a kite, working the rudders by cords. Although they obtained satisfactory results in this way they realised fully that actual gliding experience was necessary before the tests could be considered practical.

A series of actual measurements of lift and drift of the machine gave astonishing results. 'It appeared that the total horizontal pull of the machine, while sustaining a weight of 52 lbs., was only 8.5 lbs., which was less than had been previously estimated for head resistance of the framing alone. Making allowance for the weight carried, it appeared that the head resistance of the framing was but little more than fifty per cent of the amount which Mr Chanute had estimated as the head resistance of the framing of his machine. On the other hand, it appeared sadly deficient in lifting power as compared with the calculated lift of curved surfaces of its size... we decided to arrange our machine for the following year so that the depth of curvature of its surfaces could be varied at will, and its covering air-proofed.'

After these experiments the brothers decided to turn to practical gliding, for which they moved four miles to the south, to the Kill Devil sandhills, the principal of which is slightly over a hundred feet in height, with an inclination of nearly ten degrees on its main north-western slope. On the day after their arrival they made about a dozen glides, in which, although the landings were made at a speed of more than twenty miles an hour, no injury was sustained either by the machine or by the operator.

'The slope of the hill was 9.5 degrees, or a drop of one foot in six. We found that after attaining a speed of about twenty-five to thirty miles with reference to the wind, or ten to fifteen miles over the ground, the machine not only glided parallel to the slope of the hill, but greatly increased its speed, thus indicating its ability to glide on a somewhat less angle than 9.5 degrees, when we should feel it safe to rise higher from the surface. The control of the machine proved even better than we had dared to expect, responding quickly to the slightest motion of the rudder. With these glides our experiments for the year 1900 closed. Although the hours and hours of practice we had hoped to obtain finally dwindled down to about two minutes, we were very much pleased with the general results of the trip, for, setting out as we did with almost revolutionary theories on many points and an entirely untried form of machine, we considered it quite a point to be able to return without having our pet theories completely knocked on the head by the hard logic of experience, and our own brains dashed out in the bargain. Everything seemed to us to confirm the correctness of our original opinions: (1) That practice is the key to the secret of flying; (2) that it is practicable to assume the horizontal position; (3) that a smaller surface set at a negative angle in front of the main bearing surfaces, or wings, will largely counteract the effect of the fore and aft travel of the centre of pressure; (4) that steering up and down can be attained with a rudder without moving the position of the operator's body; (5) that twisting the wings so as to present their ends to the wind at different angles is a more prompt and efficient way of maintaining lateral equilibrium than shifting the body of the operator.'

For the gliding experiments of 1901 it was decided to retain the form of the 1900 glider, but to increase the area to 308 square feet, which, the brothers calculated, would support itself and its operator in a wind of seventeen miles an hour with an angle of incidence of three degrees. Camp was formed at Kitty Hawk in the middle of July, and on July 27th the machine was completed and tried for the first time in a wind of about fourteen miles an hour. The first attempt resulted in landing after a glide of only a few yards, indicating that the centre of gravity was too far in front of the centre of pressure. By shifting his position farther and farther back the operator finally achieved an undulating flight of a little over 300 feet, but to obtain this success he had to use full power of the rudder to prevent both stalling and nose-diving. With the 1900 machine one-fourth of the rudder action had been necessary for far better control.

Practically all glides gave the same result, and in one the machine rose higher and higher until it lost all headway. 'This was the position from which Lilienthal had always found difficulty in extricating himself, as his machine then, in spite of his greatest exertions, manifested a tendency to dive downward almost vertically and strike the ground head on with frightful velocity. In this case a warning cry from the ground caused the operator to turn the rudder to its full extent and also to move his body slightly forward. The machine then settled slowly to the ground, maintaining its horizontal position almost perfectly, and landed without any injury at all. This was very encouraging, as it showed that one of the very greatest dangers in machines with horizontal tails had been overcome by the use of the front rudder. Several glides later the same experience was repeated with the same result. In the latter case the machine had even commenced to move backward, but was nevertheless brought safely to the ground in a horizontal position. On the whole this day's experiments were encouraging, for while the action of the rudder did not seem at all like that of our 1900 machine, yet we had escaped without difficulty from positions which had proved very dangerous to preceding experimenters, and after less than one minute's actual practice had made a glide of more than 300 feet, at an angle of descent of ten degrees, and with a machine nearly twice as large as had previously been considered safe. The trouble with its control, which has been mentioned, we believed could be corrected when we should have located its cause.'

It was finally ascertained that the defect could be remedied by trussing down the ribs of the whole machine so as to reduce the depth of curvature. When this had been done gliding was resumed, and after a few trials glides of 366 and 389 feet were made with prompt response on the part of the machine, even to small movements of the rudder. The rest of the story of the gliding experiments of 1901 cannot be better told than in Wilbur Wright's own words, as uttered by him in the lecture from which the foregoing excerpts have been made.

'The machine, with its new curvature, never failed to respond promptly to even small movements of the rudder. The operator could cause it to almost skim the ground, following the undulations of its surface, or he could cause it to sail out almost on a level with the starting point, and, passing high above the foot of the hill, gradually settle down to the ground. The wind on this day was blowing eleven to fourteen miles per hour. The next day, the conditions being favourable, the machine was again taken out for trial. This time the velocity of the wind was eighteen to twenty-two miles per hour. At first we felt some doubt as to the safety of attempting free flight in so strong a wind, with a machine of over 300 square feet and a practice of less than five minutes spent in actual flight. But after several preliminary experiments we decided to try a glide. The control of the machine seemed so good that we then felt no apprehension in sailing boldly forth. And thereafter we made glide after glide, sometimes following the ground closely and sometimes sailing high in the air. Mr Chanute had his camera with him and took pictures of some of these glides, several of which are among those shown.

'We made glides on subsequent days, whenever the conditions were favourable. The highest wind thus experimented in was a little over twelve metres per second--nearly twenty-seven miles per hour.

It had been our intention when building the machine to do the larger part of the experimenting in the following manner:--When the wind blew seventeen miles an hour, or more, we would attach a rope to the machine and let it rise as a kite with the operator upon it. When it should reach a proper height the operator would cast off the rope and glide down to the ground just as from the top of a hill. In this way we would be saved the trouble of carrying the machine uphill after each glide, and could make at least ten glides in the time required for one in the other way. But when we came to try it, we found that a wind of seventeen miles, as measured by Richards' anemometer, instead of sustaining the machine with its operator, a total weight of 240 lbs., at an angle of incidence of three degrees, in reality would not sustain the machine alone--100 lbs.--at this angle. Its lifting capacity seemed scarcely one third of the calculated amount. In order to make sure that this was not due to the porosity of the cloth, we constructed two small experimental surfaces of equal size, one of which was air-proofed and the other left in its natural state; but we could detect no difference in their lifting powers. For a time we were led to suspect that the lift of curved surfaces very little exceeded that of planes of the same size, but further investigation and experiment led to the opinion that (1) the anemometer used by us over-recorded the true velocity of the wind by nearly 15 per cent; (2) that the well-known Smeaton co-efficient of.005 V squared for the wind pressure at 90 degrees is probably too great by at least 20 per cent; (3) that Lilienthal's estimate that the pressure on a curved surface having an angle of incidence of 3 degrees equals.545 of the pressure at go degrees is too large, being nearly 50 per cent greater than very recent experiments of our own with a pressure testing-machine indicate; (4) that the superposition of the surfaces somewhat reduced the lift per square foot, as compared with a single surface of equal area.