. Animal flight; a record of observation . 164 ANIMAL FLIGHT. shown in fig. 48, the wing must bend in the oppositedirection. As a matter of fact, the secondary quills areattached to the wing bones in such a way that theyeasily yield to the air pressure during the up-stroke,under all circumstances. I have once or twice observeda vulture flapping towards the west in the afternoon,and noticed that during the up-stroke the sun illuminatedthe underside of the wings. During the down-strokethe underside of the wings remained in shadow, thusproving that there is a difference in the inclination ofthe w
. Animal flight; a record of observation . 164 ANIMAL FLIGHT. shown in fig. 48, the wing must bend in the oppositedirection. As a matter of fact, the secondary quills areattached to the wing bones in such a way that theyeasily yield to the air pressure during the up-stroke,under all circumstances. I have once or twice observeda vulture flapping towards the west in the afternoon,and noticed that during the up-stroke the sun illuminatedthe underside of the wings. During the down-strokethe underside of the wings remained in shadow, thusproving that there is a difference in the inclination ofthe wings during the up and down-strokes of the natureabove suggested. But it has already beenshown that the secondaryquill feathers are so attached _ FlG- 48- - . , . , Pied kingfisher in fast horizontal that they do not yield On flight, showing the position of a the down-stroke if the wing section of %.^L during theis fully extended. Therefore, if horizontal flight resembles poising inthe manner suggested, ordinary horizontal flappingfligh
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