He repaired his wing and repeated the test a few days later. A violent wind gust came; picked him up from the earth, and whelmed him over. In his alarm he allowed his “wish-bone” to spread, and the wings to fold up like those of a butterfly at rest, pinching him between them like a nut in a nutcracker. One wonders whether the overwheeling vultures witnessed this gentleman’s flight with any sense of humor.
After mature reflection, Mouillard concluded that he should give his aëroplane a rudder, and flex the wings, in order to insure adequate control. But here he halted, being a poor man unskilled in the art of construction. He had reached the limit of his endowments. He had observed faithfully and described charmingly the wonderful flights of various birds; but he must leave to his technical successors the pleasure of imitating or excelling those extraordinary maneuvers—leave them the pleasure, the sacrifice, the long years of toil and danger, accompanied perhaps by indiscriminate applause or derision.
In the meantime another distinguished disciple of the birds was energetically at work in Germany. No less ardent than Le Bris, or Mouillard, Otto Lilienthal was far better equipped and circumstanced. He was a graduate of the Potsdam Technical School, and a student for three years in the Berlin Technical Academy. He was engaged in practical construction ten years in various machine shops at Berlin. After 1880 he operated a flourishing machine factory of his own. From boyhood he with his brother Gustavus had carefully studied the flight of birds, and had made numerous experiments in aviation. On moonlight nights in their little home place of Anclam, in Pomerania, the boys would run downhill, flapping their home-made wings, like Dædalus and Icarus, but with no other danger than discovery and teasing by their neighbors. At Potsdam and Berlin they continued to experiment and to construct wings of increasing size and power. Thus Otto Lilienthal reached early manhood thoroughly trained by his long courses in the technical schools and shops, brimming with well pondered ideas, strengthened by continuous observation and experiment, and in financial circumstances which permitted him to devote time and money to the unremunerative pursuit of aviation. To this may be added that his mature years were cast in a time when the allied sciences could aid him far more than they had aided his predecessors of the preceding generation.
After careful research for the most efficient form of alar surface, Lilienthal resolved to imitate the birds. First he would build a pair of arched wings, and learn to coast down the atmosphere, balancing and steering like a stork in the gusty and treacherous current. He would thus acquire the pilot’s skill, and ascertain the towline power required to sustain a given weight. Then he would add a suitable propelling mechanism, test it cautiously, and acquire the mastery of dynamic flight. Incidentally, perhaps, he would learn to ride all over creation without motive power; for he was convinced that certain great birds soar without muscular effort, and that man could acquire this delightful art in favorable weather. To strengthen the plausibility of that doctrine, he announced his discovery that the general trend of the wind is three and a half degrees upward, a fact inexplicable and almost incredible to his illustrious confrère of the Smithsonian Institution.[26] Such was Lilienthal’s ample program; more, indeed, than he would live to accomplish, though possibly not beyond his power of achievement, if he could have lived to enjoy the hale long years of his illustrious countryman aëronaut, Count Von Zeppelin.
In the year 1891 Lilienthal made his first series of trials in sailing flight. His glider was the bird-shaped apparatus shown in [Plate XVI], made of willow wood covered with waxed sheeting. It weighed about 40 pounds, and spread 107 square feet of surface. Taking this in his arms he first ran 24 feet along a raised board and jumped off, gliding through still air. Then, elevating the board to a height of six feet, he repeated the run, jump and glide, always landing very softly. Thus he became “king of the air in calm weather,” a title still creditably sustained by his numerous successors of the present day; for as yet no one “mounts the whirlwind and directs the storm.”
Next he went to some little mounds in a field beyond Werder, and jumped from these, gradually lengthening his flights till he attained a range of nearly 80 feet. As he was now gliding in light winds, he found it necessary to add a vertical rudder, in order to preserve his balance easily, and keep his bow toward the direction of the wind. His complete apparatus was, therefore, a birdlike affair, with two rigid wings and a double tail for steering vertically and horizontally. He found also that he could fly longer and alight more softly when the wind was blowing—an obvious possibility.
Encouraged by this experience Lilienthal explored the country about Berlin for sailing ground where he could make long glides, whatever the direction of the wind. Such a region he found near Rathenow, where the Rhinow hills, covered with grass and heather, slope gently upward from the flat plowland to a height of over 200 feet. This he thought an ideal coasting ground; for he felt the aërial currents very smooth, and he could always select clear land sloping ten to twenty degrees toward the wind. Here in the summer of 1893, with a new and improved glider, he made many flights, finally ranging from 200 to 300 yards, steering up and down, or to right and left at will; sometimes pausing in mid air, and several times returning to the starting point. This was more than coasting; for a mere coaster never maintains, nor returns to, his original level. It was a fair start at true soaring, the ideal locomotion. A glorious sport it was, sailing like an eagle high over the landscape and over the heads of the astonished spectators.
The new machine resembled its predecessors in form and maneuver; but differed in dimensions. It was a birdlike craft with parabolically arched wings and a double tail. It measured 7 meters across, spread 14 square meters of surface, weighed with the rider 200 pounds, and in calm air could sail down a slope of 9°, at a speed of 9 meters per second. This was very efficient sailing, the work of gravity being hardly two horse power. With the man lying prone, as eventually planned, the economy would be still greater.
PLATE XVI.