VULTURES. 15 



eyes. They moved in large curves, sweeping in 

 circles, descending and ascending without once 

 flapping. As they glided close over my head, I 

 intently watched from an oblique position the 

 outlines of the separate and terminal feathers of 

 the wing ; if there had been the least vibratory 

 movement, these would have blended together, 

 but they were seen distinct against the blue sky. 

 The head and neck were moved frequently, and 

 apparently with force ; and it appeared as if the 

 extended wings formed 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 then when again 

 expanded with an altered inclination, the mo- 

 mentum 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 plane in that fluid 

 (in which there is so little friction) cannot be 

 great; and this force is all that is wanted. The 

 movement of the neck and body of the Condor, 

 we must suppose, is sufficient for this. How- 

 ever this may be, it is truly wonderful and beau- 

 tiful to see so great a bird, hour after hour, with- 

 out any apparent exertion, wheeling and gliding 

 over mountain and river." 



Mr. Darwin supposes that the Condor breeds 

 only once in two years, that it lays two large 

 white eggs on the bare rock, and that the young 

 are very long in coming to maturity. 



