FLIGHT. 277 



rising on tiptoe, and puffing out and balancing his 

 body, to feel whether he has thrown enough of air 

 into the bones and feathers to float him along. He 

 then crouches back in order to give additional force 

 to his spring, and forthwith leaps up into the air, at 

 the same time rapidly raising his wings from the 

 sides, but keeping the individual feathers close to- 

 gether like a folded fan, which he takes care not to 

 open till he begins to bring them down. For this 

 purpose he spreads them out to their utmost ex- 

 tent, and then striking the air with all his force, its 

 resistance pushes him upward, and he bounds aloft 

 towards his tree-perch, or wherever else he wishes 

 to go. The same series of motions, first raising 

 the folded wings, and then forcibly bringing down 

 the spread wings, must be incessantly repeated du- 

 ring the flight of every bird ; in the same way a 

 swimmer, by pressing the water downward with 

 his spread hands, keeps himself afloat, and, by di- 

 recting the motion obliquely backward, is thereby 

 pushed forward. It may also be remarked, that 

 the swimmer raises his hands before renewing the 

 stroke with the fingers closed, slanting, in a similar 

 way to the bird raising its folded wings, so as to 

 dimmish the surface opposed to the resisting me- 

 dium. The direction in which a bird can fly de- 

 pends greatly on the form of its wings ; and hence 

 Sir Everard Home justly infers, that a motion di- 

 rectly upward can only be performed by birds whose 

 wings are nearly horizontal, as the lark and the 

 quail. " In general," he says, " the wings are pla- 

 ced oblique : this is principally owing to the length 

 of their feathers, the fixed point of which is at 

 the root. When birds fly horizontally, their mo- 

 tion is not in a straight line, but obliquely upward, 

 and they allow the body to come down to a lower 

 level before a second stroke is made by the wings, 

 so that they move in a succession of curves. To 

 ascend obliquely, the wings must repeat their 

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