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 entitled _Bird 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 with flat 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.