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 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 wonderful and
beautiful to see so great a bird, hour after hour, without any
apparent exertion, wheeling and gliding over mountain and river.
APRIL 29, 1834.
From some high land we hailed with joy the white summits of the
Cordillera, as they were seen occasionally peeping through their
dusky envelope of clouds.
Pages:
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382