abandoned art in Gradually specifically problem of man science and a problem that had fascin ated him for flight his early youth he had dreamed of flying, and he techno Y he was determined to make his dream a the flight of birds and then the After models began by watching ing down his findings in his structure of birds' wings. he made experiments observations and noted the results. He proposed to into a book on the flight of birds. The book would be by beat their beating their into four parts the first of which ing their wings; the second of flight without of flight wings, and with the help the wind; general, such as that of birds, bats, fishes, animals, and in sects; the last of the mechanism of this movement." He watched the way birds use their tails as rudders and how lowering their tails gentle landings by stalling. their wings quickly they and spreading the to cut down their speed, and changing their center of gravity by moving their heads. He dissected countless birds and bats to learn how the wing opens and closes and how its muscles move it. The end of all of his work was to be an attempt at actual flight. Others, it happened, had made attempts before Leo. nardo. One, an Italian mathematician and engineer named Giovanni Danti, had made a short glide over and into Lake Trasimeno around l490; later he made a second attempt at gliding, which resulted in a broken leg. Leonardo was cer- tain he could succeed where Danti had failed. A bird," he wrote, "is an instrument working according to mathematical law, which instrument it is within the capac- ity of man to reproduce His investigations were spread over a long period of time, during which he watched and studied birds and invented various contraptions that would demonstrate how different surfaces are affected by the move- ment of air. Among his notes is a drawing of a parachute