Identifier: animallocomotion00pett (find matches)
Title: Animal locomotion or walking, swimming, and flying : with a dissertation on aëronautics
Year: 1873 (1870s)
Authors: Pettigrew, James Bell, 1834-1908
Subjects: Animal locomotion Physiology Aeronautics
Publisher: London : Henry S. King & Co.
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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s made to descend, it gradually, in virtue ofits simultaneously rotating upon its long and short axes,makes a certain angle with the horizon as represented at b.The angle is increased at the termination of the down strokeas shown at c, so that the wing, particularly its posteriormargin, during its descent (A), is screwed or crushed downupon the air with its concave or biting surface directed for-wards and towards the earth. The same phenomena areindicated at a b c of fig. 85, but in this figure the wing isrepresented as travelling more decidedly forwards during itsdescent, and this is characteristic of the down stroke of theinsects wing—the stroke in the insect being delivered in avery oblique and more or less horizontal direction (figs. 64,65, and 66, p. 139 ; fig. 71, p. 144). The forward travel ofthe wing during its descent has the effect of diminishing theangles made by the under surface of the wing with the hori-zon. Compare b c d of fig. 85 with the same letters of fig. 84. 7:
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\S Fig. S6. At fig. 88 (p. 166) the angles for a similar reason are stillfurther diminished. This figure (88) gives a very accurateidea of the kite-like action of the wing both during itsdescent and ascent. The downward screwing of the posterior margin of the and forward direction at the beginning of the down stroke—the downward andforward rotation securing additional elevating power for the wing. The pos-terior margin of the wing in bats and birds, unless they are flying downwards,never rises above the anterior one, either during the up or down stroke. L 162 ANIMAL LOCOMOTION. wing during the down stroke is well seen in the dragon-fly,represented at fig. 86, p. 161. Here the arrows rs indicate the range of the wing. Atthe beginning of the down stroke the upper or dorsal sur-face of the wing (i d f) is inclined slightly upwards and for-wards. As the wing descends the posterior margin (if)twists and rotates round the anterior margin (i d)., and greatlyincreases the angle of inclinati

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