brought forth from his floating laboratory on Lake Constance the first of his airships.

Through disaster after disaster and grievous hardships, Count Zeppelin pushed his work from 1900 to 1910, when he had his first passenger machine ready. The maiden voyage of this first air liner was a marvel to the fortunate few traveling in such celestial style. Great progress was made between 1910 and 1914 and at the outbreak of the European War the Zeppelin was one of the most potential elements of Germany's air fleet.

Aeroplane, The.* The art of aeroplane flight presents two main groups of fliers. The first comprises the various man-kites, parachutes, gliding machines, soaring machines. These may be called passive fliers, because they carry no motive power, but ride passively on the air by the force of gravity or a towline. The second group comprises the bird-like flapwing machines called orthopters"; the screwlift fliers called "helicopters"; the aeroplanes, also called monoplanes, biplanes, triplanes, according to the number of superposed main lifting surfaces; and lastly the gyroplanes, whose sustaining surfaces may turn over and over, like a falling lath, or whirl round and round, like a boomerang. These may all be called dynamic, or power, fliers.

Disregarding the crude essays at human flight, recorded in the early histories and literature of many peoples, we may notice first the well-authenticated sketches of Leonardo da Vinci. His fertile mind conceived three distinct devices for carrying a man in the air. But he and his successors for nearly four centuries could do little more than invent. For lack of motive power they could not navigate dynamic fliers, however ingeniously constructed. Da Vinci's first design provided the operator with two wings to be actuated by the power of both arms and legs. His second design was a helicopter; an aerial screw 96 feet in diameter was to be turned by a strong and nimble artist who might, by prodigious effort, lift himself for a short time. His third scheme of flight was a framed sail on which a man could ride downward, if not upward.

Mr. Henry Woodhouse, one of the foremost aeronautic authorities, author of the Textbook - of Naval Aeronautics,' and the 'Text book of Military Aeronautics,' has summarized the work of pioneer experiments in aeronautics as follows: History has a list of some two-score of experimenters who tried to develop power flight, among whom were: Sir George Gayley, an English inventor, whose writings (180910) show that he was first to plan dynamic flight on a scientific basis. He planned an aeroplane built with slightly oblique planes, resting on a wheeled chassis, fitted with propelSamuel lers, motors and steering devices. Henson, another English inventor, in 1843, patented what was designated as an "aeriaĺ steam carriage," an aeroplane of immense size, which was to be used for passenger carrying. This carriage was never built. Another English scientist, F. H. Wenham, improved on Henson's idea, and in 1867 developed a multiplane. This model was taken up by another inventor, M. Strongfellow, who reduced the number of planes to three, making a triplane, *For a detailed discussion see AEROPLANE.

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which he fitted with a tail and two propellers. This model was shown at the exhibition of the Aeronautical Society of Great Britain in 1868. As in the case of previous inventors, nothing in this model indicated that he had any comprehension of the principles of stability or knowledge of the lifting capacity of surfaces, or of the power required for dynamic flight. Strongfellow deserves, however, much credit for building a very light motor, one of sufficient lightness to support a well-designed aeroplane. In 1872, a French inventor, named Alphonse Penaud, constructed a small monoplane. It was only a toy-two flimsy wings, actuated by a twisting rubber, but had fore-and-aft stability, something that most of the creations of the time lacked. Subsequently, in 1875, Penaud took out a patent on a monoplane fitted with two propellers, and having controlling devices. But this was not built, principally because it would have required a light motor, and the lightest available at the time weighed over 60 pounds per horse power, or 20 times the weight of the motors of to-day. Louis Pierre Mouillard, a Frenchman, having observed that large birds in flight, while seeming at rest, could go forward against the wind without a stroke of the wings, constructed a number of gliders, built on the principle of bird wings, and experimented with gliding. In 1881, he published a valuable work entitled 'L'Empire de l'Air,' which inspired many of the latter experimenters. Subsequently he invented a soaring machine, which he patented in 1892.

Pioneers of Modern Aviation. These early experimenters laid the foundations of modern aviation. They showed the supporting power of their rigid surfaces, defined the general shape and structure of the aeroplane, and prepared the work for the next generation, which was to perfect these, and find ways and means to make the aeroplane rise from the ground and maintain equilibrium in the air. This new generation came toward the close of the 19th century. These new men, the pioneers of modern aviation, were divided into two schools. The first sought to achieve soaring flight by means of kitelike apparatus, which enabled them to soar in the air against winds, their machines being lifted up and supported by the inertia of the air as kites are. second sought to develop power flight, that is, to send their kitelike machines through the air at high speed, being tracted or propelled by revolving screws actuated by motor power. The most eminent experimenters in the first schools were Otto Lilienthal, who was the chief expounder of gliding flight; P. L. Pilcher, an English follower of Lilienthal; Octave Chanute, an American follower of Lilienthal, and J. J. Montgomery, an American experimenter.

The

Lilienthal, a German, was the first to make gliding flight a science, and he first defined the value of arched wings, and the amount of pressure to be obtained at various angles of incidence. He met with untimely death while experimenting in 1896. Chanute's experiments were in the line of Lilienthal, but his great contribution was his early encouragement of the Wrights, although the Wrights did not succeed by adopting Chanute's theories.

The leaders of the second school, who actually built and tried power-driven aeroplanes,

were Clement Ader (1890-97); Sir Hiram Stevens Maxim (1890-94) and Samuel Pierpont Langley (1895-1903). Clement Ader was the first to construct an aeroplane large and powerful enough to carry a man, and the French government considered the craft of immense value and employed him to build some for the army, but as each of the two experiments toppled over at the trial and wrecked, the government refused to further finance the enterprise. While Ader was making his experiments in France, Sir Hiram Maxim was at work constructing a large multiplane for the English government, which he fitted with two steam engines of 175 horse-power. But like Ader's experiment, it toppled over at the first trial and was badly damaged, and the British government refused further backing. The experience of Samuel Pierpont Langley in America is not unlike the experience of Ader in France and Maxim in England. He was employed by the Board of Ordnance and Fortification of the United States army to construct the "Aerodrome" of his own invention. Congress appropriated $50,000 for the purpose. Langley's machine was a tandem monoplane, 48 feet from tip to tip and 52 feet from bowsprit to the end of its tail. It was fitted with a 50 horse-power engine and weighed 830 pounds. The trials of his aerodrome, two attempts to launch it, were made on 7 Oct. and 8 Dec. 1903. On both occasions the aerodrome became entangled in the defective launching apparatus, and was thrown headlong in the Potomac River-on which the launching trials were made. Following the last failure, when the aerodrome was wrecked, the press ridiculed the whole enterprise, and Congress refused to appropriate money for further experiments. The Langley aerodrome, partly reconstructed and fitted with a Curtiss motor and Curtiss controls, flew in 1913-14.

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As with the experimenters of the first school, they did not attain practical results. Their machines were usually wrecked at the first trial without giving any clue to the nature or whereabouts of the trouble. Just how much each of these contributed toward the final success it is hard to say. The matter has not yet been.defined, and, possibly, only one man Orville Wright is qualified to say. Most of these men made valuable additions to the knowledge of the science, but all of them mixed the practicable with the impracticable in such a way as to make it risky to adopt their conceptions as to the basis of actual flight, a fraction of error being enough to spoil the unity of truths that must be present, and so to end an experiment in a catastrophe. Wilbur Wright, having made exhaustive tests and dissected the theories and notions of all these pioneers, knew the exact worth of each. He could have made the valuation, but died before he had done so. In a paper on Lilienthal, which he wrote for Flying a few days before his death, he defined the causes of previous failures, and made a general rule by which all could be judged and their works valued. The realization of power flight was thus left to the 20th century and to the Wright brothers. In view of the complex problems to be solved, this achievement was stupendous.

Wilbur Wright and his brother, Orville

Wright, two men of remarkable characteristics, sons of the Rev. Milton Wright, were presented in their boyhood, 30 odd years ago, with a toy helicopter, a butterfly-shaped contrivance, consisting of paper wings fitted with a tin propeller which, when made to revolve by twisted rubber, caused the toy to shoot forward through the air. That toy fired their imaginations, and they saw it, in magnified form, capable of carrying a man.

Their attempt to fly large helicopters constructed on the idea of the toy did not bring practical results, and until 1896, they did not give the matter of artificial flights more than passing attention. In the summer of that year, however, the news of the accident and death of Otto Lilienthal, the German champion of gliding flight, stirred them to action, and they set themselves to study aerodynamics and the works of Lilienthal, Mouillard, Chanute, Maxim and Langley, the most prominent experimenters at that time. Their experiments with a glider began in the fall of 1900 at Kitty Hawk, N. C. There, on the barren sand dunes of North Carolina, these two intrepid investigators took all the theories of flight and tried them one by one only to find, after two years of hard, discouraging work, that they were based more or less on guesswork. Thereupon they cast Iaside old theories and patiently put the apparatus through innumerable gliding tests, ever changing, adding, modifying-changing again and again, advancing inch by inch, until they had, at last, developed a glider wonderfully exact, which, when fitted with a light motor, also built by them, made initial flights on 17 Dec. 1903, of from 12 to 59 seconds' duration. This, then, was the birth of the aeroplane, the flimsy, iconoclastic thing which seems to evade Newton's laws, eliminates frontiers and promises to expand civilization as much as have the steamship, the railway and electricity.

The Wrights' Success Created New Interest. The Wrights did not make their achievements public at the time; in fact, until 1908, they flew only in private. But the report of their wonderful achievement, nevertheless, went far and wide, and stimulated those who had given up experimenting and inspired others to take up experiments. Octave Chanute, in 1902, went to France and related the early successes of the Wrights with their glider, and described the general shape of the Wright machine. The result of this trip was that half a dozen enthusiasts, including Louis Bleriot, Capt. Louis Ferber, Ernest Archdeacon, and later the Voisin brothers and Albert SantosDumont_took up the work, thus founding_the mighty French school which has increased so greatly and done so much since. The first of this school to succeed was Santos-Dumont, the Brazilian aeronaut sportsman. He constructed a machine of original design, and in 1906 made short sustained flights of from 50 to 700 feet in straight line, which created a world-wide sensation at the time. Meantime others of the French school graduated and won honors. The Voisin brothers turned constructors and teachers, and with their co-operation Leon Delagrange, Henry Farman, Louis Bleriot and other prosecuted practical experiments and succeeded in getting their creations to leave the ground for modest flights. At this juncture,

in the summer of 1908, the Wrights started out to give public demonstrations, and their methods supplied and suggested to the French experimenters the means to modify and improve their aeroplanes, particularly the means of balancing them, which had, until then, been a perplexing problem. Some months before this some American enthusiasts had combined under the auspices of Mr. Alexander Graham Bell, the inventor of the telephone, and Mrs. Bell, and organized the Aerial Experiment Association. Glenn H. Curtiss, one of the experimenters, developed a suitable type of aeroplane, and in 1908-09 became proficient in piloting it, and founded a school which did much in the following years to popularize and develop aviation in America. Consult Zahm, A. F., Aerial Navigation.'

The progress in aerial locomotion from 1909-14 was very rapid in Europe - especially in France and Germany-but slow in America on account of lack of the governmental stimulus which prevailed in Europe. But even in America the progress between 1909 and 1914 was important, especially in the field of marine flying, in which field America is likely to retain its supremacy. The great stimulus to aviation throughout the world came with the outbreak of the European War. The work of aircraft in the war has been of supreme importance. The co-operation of aeroplanes with artillery has proved extraordinarily effective. Of purely fighting aeroplanes, when the war began there were none—after two years there are machines weighing 10 tons, carrying a ton of ammunition, rapid-firing machine-guns and heavy guns - literally aerial cannon.

Large airships in the war have proved disappointing when compared with the aeroplane, because they are in a cruder state of development. They have almost the size of a battleship, offering a large target, without the battleship's armor or guns. The seaplane has had many achievements to its credit in the naval operations and the types which will be equipped with aerial torpedoes will constitute a real dynamic force in the future. The development of aerial locomotion during 1914-16 has exceeded the expectations of the most sanguine enthusiast -no man can prophesy what the next decade will produce. See AEROPLANE DISTANCE AND SPEED RECORDS; AEROPLANE ALTITUDE RECORDS; AERONAUTICAL NOMENCLA

TURE.

G. DOUGLAS WARDROP, Managing Editor Aerial Age. AERONAUTICS, Military. See MILITARY AERONAUTICS.

AEROPLANE (from the Greek aer, air; planos, wandering), a term now commonly used to define a "heavier than air" flying machine equipped with fixed aerofoils or main supporting surfaces and driven by suitable motive power.

Principle. Everyone nowadays is familiar with the appearance of an aeroplane, but many there are, nevertheless, who do not know what, scientifically speaking, an aeroplane is. They see the machine on the ground; they observe someone giving frantic tugs at something that moves in jerks: they hear a roar, which they know must come from an engine; they per

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ceive that, in starting, the machine runs for a while along the ground before rising gently into the air; but still they do not know why the aeroplane flies.

It has something to do with the wings, of course, but how? That is the question at which the average lay mind stops short, not for ability to understand the problem, but generally for lack of some appropriate explanation that will bring what is fundamentally a very simple phenomenon out of its proper sphere of aeronautical science into the realm of everyday things that are comprehended by

common sense.

There is an elusive aspect of the general view, and only one, that is apt to hide itself from the uninitiated unless brought prominently into the full light of the mind in the very first instance and that is the significance of a simple scientific expression much used in aviation, namely, "relative motion." If the man in the street saw an aeroplane apparently standing still in the air it would not occur to him to think that the machine must be flying through the wind at its full speed and that its relative motion in the air is quite unaffected by its motion relatively to the ground on which he is standing. Yet the same man knows very well that if he starts running on a calm day he will feel a slight breeze in his face, which is solely the result of his own relative motion through the air. He is also aware that if he puts his head out of an express railway car he will encounter half a gale of wind notwithstanding that the leaves of the trees may show not so much as a tremor. If, instead of putting his head out of the window, he were to take a sheet of stiff cardboard and put that outside he would have a still more practical demonstration of the force of the relative wind which supports the aeroplane in its flight. If the train is moving fast the cardboard will exhibit a violent tendency to flap upwards and downwards with the least variation from its truly edge-on horizontal position. It is at this point that the embryo scientist begins to think really hard. mind perceives an unsuspected fact that he senses to be of great importance. He has observed that by slightly raising the front edge of the piece of cardboard so that it is at a slight angle to its line of motion, instead of being truly edge-on, an extremely strong lifting force acts on the cardboard, although its resistance to the air is but little more than it was when the cardboard was edge-on. So pronounced is the preponderating value of the lifting effort over the resistance at very small angles that anyone making this experiment would at once conclude that if he wished the wind to support a weight he would certainly arrange some sort of a surface beneath it, like a table, but tilted so as to have only a slight angle of inclination to the line of its flight through the air.

His

An aeroplane has its table-like supporting surfaces so arranged as to get the best lifting effect for the least effort, having regard, of course, for the conditions under which the machine is designed to fly. It is clear, merely from a glance at a number of aeroplanes, that they are not all exactly alike in this respect, but it will be noticed that they all have one point in common which is that the surface