This gliding apparatus is not unlike that with which M. Chanute and other early experimenters tested the qualities of air currents. The apparatus here shown is being drawn by an automobile, so that its action is virtually that of a kite. This picture was taken at Morris Park, New York, in 1909. The descent was made too abruptly and the aviator was seriously injured.
The great German scientist, Helmholtz, after years of careful study, finally reached the conclusion that man would never be able to fly by his own power alone. But, as we have seen, Professor Langley had shown that in these mysterious questions pertaining to flight even a Newton could be wrong; and why not Helmholtz? Otto Lilienthal, also a German, thought that his fellow-countryman was wrong. For years he had made a study of the flight of birds, and his studies had led him to the same conclusions that have usually been reached by every student of the subject, both before and since—that soaring flight, without any flapping movement, is possible under certain conditions; that curved surfaces can acquire a horizontal motion by the action of the wind alone, "when their curvature bears a certain relation to their superficies"—in short, a relation represented exactly by the wings of birds.
It was not supposed by Lilienthal, or by any of the members of the school of aviators, that simply by making a device that reproduced the proportions and shape of a bird any person might mount and fly. But it was believed that, given such a device, a man might learn to fly with practice. Lilienthal, therefore, constructed a flying-machine with correctly curved surfaces made of linen stretched over a light wooden frame, the total area being about fourteen square yards, and the whole machine weighing only about forty pounds. In the center was an aperture where the operator was stationed, holding the frame in position by his arms. Obviously, as no flapping motion in imitation of a bird's wings was possible, some other means of giving the necessary impetus for horizontal flight was necessary, and here again the study of birds suggested a method.
It is a well-known fact that certain soaring birds cannot leave the ground when once they have alighted, except by an initial run to acquire the necessary speed; and every goose hunter is familiar with the manner in which these birds run along the surface of water, flapping their wings and skimming along some distance before they acquire sufficient velocity to mount into the air. A description of a similar action of an eagle in leaving the earth, written by a careful observer a few years ago, has become classic. This huntsman had come upon an eagle which had alighted upon the sandy banks of the Nile, and had fired at it, thus stimulating the bird to its utmost energy in getting into flight. Yet on examining the foot-marks made in the sand it was found that, even under these circumstances, the bird had been obliged to run "full twenty yards before he could raise himself from the earth. The marks of his claws were traceable on the sandy soil," says the writer, "as, at first with firm and decided digs, he found his way, but as he lightened his body and increased his speed with the aid of his wings, the imprints of his talons gradually merged into long scratches."
It is evident that if such a master of the art of flying as an eagle must thus acquire initial velocity before flight is possible, a human novice must do considerably more. The method that would naturally suggest itself would be that of running down the slope of a hillside, and Lilienthal adopted this method, beginning his flights by running down the gentle slope of a hill against the wind, until the requisite momentum was acquired. This was, indeed, a reversion to some of the oldest types of flying-machines, but with this difference—that it was the result of scientific study. The results attained proved that the theory was not visionary—that scientists had not dreamed and studied in vain. For, as little by little the experimenter gained experience, he was able to soar farther and farther in his birdlike machine, in one flight sailing a distance of twelve hundred feet. Under certain favorable wind conditions he could sail from a hilltop without the initial run, and at times he actually rose in the air to a point higher than that from which he started.
As was to be expected in the very nature of the case, Lilienthal found that part of the secret of success lay in maintaining his equilibrium and in acquiring the faculty of doing this instinctively, as a bird does. But he found, like the person learning to ride a bicycle, that this was developed by repeated efforts. The action of the machine itself was carefully studied, and various changes were made in his apparatus from time to time as experience suggested them. Among other things, feather-like sails, worked by a small motor, were attached to the edge of the wings; and two smaller frames placed one above the other were tried in place of one large frame. And still the operator continued to make successful flights in all kinds of winds, sometimes narrowly escaping disaster, but for three years always coming to the ground safely. His confidence increased day by day, and as his remarkable performances multiplied it seemed as if it would only be a matter of time until he would be able to imitate the soaring bird and sail almost as he pleased.
In writing of his experiences when, as it sometimes happened, he found himself practically motionless in the air at a point higher than that from which he started, he says: "I feel very certain that if I leaned a little to one side, and so described a circle, and further partook of the motion of the lifting air around me, I should sustain my position. The wind itself tends to direct this motion; but then it must be remembered that my chief object in the air is to overcome the tendency of turning to the right or left, because I know that behind or under me lies the hill from which I started, and with which I would come in rough contact if I allowed myself to attempt this circle-sailing. I have, however, made up my mind, by means of either stronger wind or by flapping the wings, to get higher up and farther away from the hills, so that sailing round in circles, I can follow the strong, uplifting current, and have sufficient air-space under and around me to complete with safety a circle, and lastly to come up against the wind again to land."
Before he was ready to make this attempt, however, Lilienthal was killed by a fall caused by a treacherous gust of wind which tilted his machine beyond his control and hurled him to the ground.
Again the expectant world of aerial navigators was thrown into despondency by the happening of the long expected—expected, and yet not expected; for Lilienthal had made so many daring flights under so many trying conditions, always managing to alight safely, that a feeling of confidence had succeeded that of distrust. It was almost like a bolt from a clear sky, therefore, when the news was flashed around the world that Lilienthal was no more. But science has never yet been daunted by the fear of death. Like a well-formed battle-line in which the place of the fallen is always quickly filled, there is always a warrior-scientist ready to sacrifice anything for the cause. And so, although Lilienthal was gone, the work he had carried so far toward success was continued by others, Chanute and Hering, the American "soaring men," and later eclipsed by the Wright brothers, who were finally to solve the problem.