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 wit 
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 
diminish 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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