But they were not discouraged, and continued to build simple, easily-constructed machines--from each of which, although it would not fly, they learned a useful lesson. One, for instance, they made with wings of goose feathers, sewn upon tape and fixed to wooden spars. These wings, when finished, they fastened upon hoops which were strapped to the operator’s chest and hips; and he could, by means of a lever and a stirrup arrangement, beat the wings up and down by movements of his legs. This machine they hung from a beam in an attic in their house; but although the wings _did_ flap, and actually showed some tendency to lift, the apparatus was soon consigned to a lumber-room, and they were busy with plans for another. What impressed Otto Lilienthal was the fact that, even when provided by Nature with a perfect flying apparatus, the birds of the air had to learn to use it. They could not just leap upward and “ride the wind” as men had tried to do; they needed to take their first fluttering flights--beating their wings anxiously and often falling back to earth, because they did not know as yet how to use these wings. Particularly did Lilienthal study the flight of storks. He obtained young birds from neighbouring villages, and fed them in his garden with meat and fish while he watched their efforts to learn to fly, and studied that marvellous piece of mechanism--the wing Nature had given them. Writing of his observations in a book he afterwards prepared, called _Birdflight as the Basis of Aviation_, Lilienthal describes the antics of young storks upon the lawn behind his house: “When the actual flying practice begins, the first attention is devoted to the determination of the wind direction; all the exercises are practised against the wind, but since the latter is not so constant on the lawn as on the roofs, progress is some-what slower. Frequently a sudden squall produces eddies in the air, and it is most amusing to watch the birds dancing about with lifted wings in order to catch the wind which changes from one side to another, all round. Any successful short flight is announced by joyful manifestations. When the wind blows uniformly from an open direction over the clearing, the young stork meets it, hopping and running; then turning round, he gravely walks back to the starting-point and again tries to rise against the wind.