ZOOLOGY. 



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 tin- 

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

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



Fig. 225. Wing of the Falcon.* 



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 ; 

 the condor (American vulture, Vulture of the Andes) and the 

 sea bird called frigate, are good examples of such powers of 

 flight. The dwelling of the condor is on the lofty peaks of 

 the Cordilleras, from whence he descends to the ocean at a 

 sweep, regardless of the effect of rapid changes in the tem- 

 perature and in the pressure of the atmosphere. They are 

 said to be strong enough to carry off in their talons >Wp 

 and lamas, and when united in numbers, to attack and kill an 

 ox.f The birds called frigates have the wings proportionally 

 longer, and are met with in tropical seas at the distance of 

 four hundred leagues from land. 



To rise vertically, the wings of the bird must be carried 

 horizontally; but this is seldom the case, and from the 

 obliquity of their position they impress on the motions of 

 the bird an oblique ascensional movement; occasionally this 

 obliquity is so great that, in order to rise vertically through 



* a, rtmigeg, or primary quills of the hand: 6, secondary quills, or those 

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



t The South African Vultures, which I have seen in vast numbers in 

 Southern Africa, have the same habits; they are a cowardly bird, not- 

 withstanding their strength and size. R. K. 



