312 ZOOLOGY. 



wings ; they must not be confounded with the so-called wings 

 of bats, which we have already seen to be of an entirely dif- 

 ferent nature : they are formed of stiff feathers or quills, 

 which require to be fixed only at their base, and the hand in 

 consequence ceases to present any appearance of fingers. 



432. The large quills of the wings are called remiges, 

 and it is more on their length and strength than on the extent 

 of the bones, that the power of flight depends. Each time 

 the bird prepares for flight he raises the arm and its plumage 

 unfolded ; then he enfolds it by extending the arm, at the 

 same time suddenly depressing it : the air which is struck 

 forms the point of support and resistance to a downward 

 movement ; upon it he rises like a projectile, and the impul- 

 sion once given to the body is maintained and directed by the 

 same instruments and movements : the bird would soon fall 

 to the earth by the force of gravity, but before the speed 

 acquired by the first effort is exhausted, a second and a third 

 take place, continuing the living projectile in its course. 



b 



Fig. 288. Wing of the Falcon.* 



Whilst the bird is being thus suspended in the air, it 

 becomes necessary for it to maintain its equilibrium in this 

 position ; and in order to secure this, its centre of gravity 

 ( 285) must be placed under the shoulders, and as low as 

 possible ; for this reason, during flight the bird carries the 

 head well forward, the neck being on the stretch, and the 

 body heaped together, as it were, into an oval form. 



It is obvious, on the plainest mechanical principles, that, all 

 things being equal, the faculty and power of flight will be in 

 the ratio of the extent of the wings, these being the moving 

 force ; and in fact all birds remarkable for their power of 

 sustaining a long and rapid flight have large wings, the oppo- 

 site being the case with birds of low, slow, and short flight ; 



* a, remiges, or primary quills of the hand ; b, secondary quills, or those 

 of the fore-arm ; d y bastard quills, or those of the thumb. 



