THE FLIGHT OF BIRDS. 
CHAPTER I. 
GLIDING. 
RESISTANCE OF AIR—LIFT AND DRIFT—CURVE OF WINGS— 
AREA OF SUPPORTING SURFACE. 
Nort 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 
B 
