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 position, 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 
distinctly 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 the tail acted. If the bird wished to descend, the 
wings for a moment collapsed; and then 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 counter- 
balance its gravity. The force to keep up the momentum of a 
body moving in a horizontal plane in the air (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. However this may be, it is truly 
27 
