THE FLIGHT OF BIRDS. 



CHAPTER I. 

 GLIDING. 



RESISTANCE OF AIR LIFT AND DRIFT CURVE OF WINGS 



AREA OF SUPPORTING SURFACE. 



Not long ago the sight of a sparrow on the wing, 

 or even the sight of a lark rising in air and singing 

 as he rose, excited but little interest or wonder in 

 the mind of the average man. It came natural 

 to birds to fly, and to fly so perfectly that they 

 concealed their art. If they had had difficulty in 

 flying, there would have been matter for astonish- 

 ment. But why waste any wonder on the easy 

 flight of a lark or a sparrow ? Such familiar things 

 were taken for granted and seemed to call for no 

 explanation. As soon, however, as men began to 

 emulate birds — gliding downwards first from some 

 elevated position and, later, by means of powerful 

 engines, rising from the ground — then there was 

 less disposition to take the bird's flight as a matter 

 of course. The bird too, it was felt, had once 

 been a beginner. He too had had difficult problems 

 to solve and had solved them long ago, the very 

 perfection of his methods making it difficult to 



