. Animal locomotion, or Walking, swimming, and flying, with a dissertation on aëronautics. Animal locomotion; Aeronautics. PROGRESSION IN OK THROUGH THE AIR. 161 When the wing is made to descend, it gradually, in virtue of its simultaneously rotating upon its long and short axes, makes a certain angle with the horizon as represented at J. The angle is increased at the termination of the down stroke as shown at c, so that the wing, particularly its posterior margin, during its descent (A), is screwed or crushed down upon the air with its concave or biting surface directed for- wards and towards
. Animal locomotion, or Walking, swimming, and flying, with a dissertation on aëronautics. Animal locomotion; Aeronautics. PROGRESSION IN OK THROUGH THE AIR. 161 When the wing is made to descend, it gradually, in virtue of its simultaneously rotating upon its long and short axes, makes a certain angle with the horizon as represented at J. The angle is increased at the termination of the down stroke as shown at c, so that the wing, particularly its posterior margin, during its descent (A), is screwed or crushed down upon the air with its concave or biting surface directed for- wards and towards the earth. The same phenomena are indicated at 6 c of fig. 85, but in this figure the wing is represented as travelling more decidedly forwards during its descent, and this is characteristic of the down stroke of the insect's wing—the stroke in the insect being delivered in a very oblique and more or less horizontal direction (figs. 64, 65, and 66, p. 139 ; fig. 71, p. 144). The forward travel of the wing during its descent has the efl[ect of diminishing the angles made by the under surface of the wing with the hori- zon. Compare bed of fig. 85 with the same letters of fig. Pig, 86. At fig. 88 (p. 166) the angles for a similar reason are still further diminished. This figure (88) gives a very accurate idea of the kite-like action of the wing both during its descent and ascent. The downward screwing of the posterior margin of the and forward direction at the beginning of the down stroke—the downward and forward 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 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Pettigrew, James Bell,
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectaeronau, bookyear1874
