200 CHARLES DARWIN 



Often when lying down to rest on the open plains, on 

 looking upwards, I have seen carrion-hawks sailing through 

 the air at a great height. Where the country is level I do 

 not believe a space of the heavens, of more than fifteen de- 

 grees above the horizon, is commonly viewed with any at- 

 tention by a person either walking or on horseback. If such 

 be the case, and the vulture is on the wing at a height of 

 between three and four thousand feet, before it could come 

 within the range of vision, its distance in a straight line 

 from the beholder's eye, would be rather more than two 

 British miles. Might it not thus readily be overlooked? 

 When an animal is killed by the sportsman in a lonely valley, 

 may he not all the while be watched from above by the 

 sharp-sighted bird? And will not the manner of its descent 

 proclaim throughout the district to the whole family of 

 carrion-feeders, that their prey is at hand? 



When the condors are wheeling in a flock round and 

 round any spot, their flight is beautiful. Except when rising 

 from the ground, I do not recollect ever having seen one 

 of these birds flap its wings. Near Lima, I watched several 

 for nearly half an hour, without once taking off my eyes: 

 they moved in large curves, sweeping in circles, descending 

 and ascending without giving a single flap. As they glided 

 close over my head, I intently watched from an oblique posi- 

 tion, the outlines of the separate and great terminal feathers 

 of each wing; and these separate feathers, if there had been 

 the least vibratory movement, would have appeared as if 

 blended together; but they were seen distinct against the 

 blue sky. The head and neck were moved frequently, and 

 apparently with force; and the extended wings seemed to 

 form the fulcrum on which the movements of the neck, body, 

 and tail acted. If the bird wished to descend, the wings 

 were for a moment collapsed; and when again expanded 

 with an altered inclination, the momentum gained by the 

 rapid descent seemed to urge the bird upwards with the 

 even and steady movement of a paper kite. In the case of 

 any bird soaring, its motion must be sufficiently rapid so 

 that the action of the inclined surface of its body on the 

 atmosphere may counterbalance its gravity. The force to 

 keep up the momentum of a body moving in a horizontal 



