Men have always wanted to be able to fly. So long as there have been birds to watch, so long have men of speculative minds wondered at the secret of their flight. Early in recorded history men built ships to sail across the seas, but the problem of air navigation has always baffled them. The balloon came into being, but the balloon for years was only a toy, dependent on the wind’s whim, and of the least possible service to men. The problem of aerial navigation was to master the currents of the air as the sailing-vessel and the steamship had overcome the waves and tides at sea. The history of invention often shows that some great thinker, or school of thinkers, has stated a scientific conclusion that generations of later men have never dared to question. The laws of Aristotle in regard to falling bodies were never doubted until Galileo began to wonder if they could be true. Sir Isaac Newton had stated, and mathematical computations had proved his words, that a mechanical flying-machine was an impossibility. Any such machine must be heavier than the air it flew in. The weight of Newton’s authority and the weight of figures were compelling facts, such as scientists had no mind to doubt. But in spite of these facts men could see that birds flew, although they were often a thousand times heavier than the air they went through. And that sight kept men speculating, in spite of all the figures and scientific dicta of the ages. It was known for centuries that if a kite was held in position by a string reaching to the ground the wind blowing against it would keep it supported in the air. Now if the kite, instead of being stationary in moving air, were to be moved constantly through quiet air it would also stay up. The motive power might be supplied by a motor and propellers, but in order to do away with the string which holds the kite in position the aeroplane, which is only a big kite in principle, must have some way of balancing itself so that it will stay in the proper position in the air. A German engineer, Otto Lilienthal, made a study of the mechanics of birds’ flights, and determined to learn their secret by actual trial. He built wings that were similar to those of the hawk and buzzard, the great soaring birds, and in 1891 he began to throw himself from the tops of hills, supported by these wings, and glided through the air into the valleys. In this way he learned new laws of flight, contradicting many theories of the scientists, and opening a new world of speculation. But in August, 1896, his wings broke in a sudden gust of wind, he fell fifty feet, and died of a broken back.