. Animal flight; a record of observation . striking the wall of the shed B is deflected upwards. C C, directionof gliding flight of the cheel. At D the outside wing is shown flexedand advanced. For the sake of clearness the cheel is representedas making a gain to windward during the turn. This did not cheel turned on its dorso-ventral axis (or nearly so), andturned approximately along the track on which it came. posterior margin of the inner part of the wing forms acurved line with the convexity upwards. Hence, though the greater part of b, .. the outside wing isflat or slightly cam-
. Animal flight; a record of observation . striking the wall of the shed B is deflected upwards. C C, directionof gliding flight of the cheel. At D the outside wing is shown flexedand advanced. For the sake of clearness the cheel is representedas making a gain to windward during the turn. This did not cheel turned on its dorso-ventral axis (or nearly so), andturned approximately along the track on which it came. posterior margin of the inner part of the wing forms acurved line with the convexity upwards. Hence, though the greater part of b, .. the outside wing isflat or slightly cam-bered, the second-aries of the centralpart of the wingare relaxed. That is Outlines of wing of a cheel. At A when slow B when medium speed flex-gliding. The horizontal line showsthe level of the centre of gravity. to say, their free ends are directed upwards. Hencethe ascending current of air striking this part of thewing is reflected, as shown by the arrows, and in beingreflected tends to drive ahead the wing in N 182 ANIMAL FLIGHT. So much for the facts. My supposition as to whatactually occurred is this : The cheel, having speed ahead,commenced its turn by a depression of the inside wingor wing-tip which was not observed. The speedahead having been abolished by this turn in the hori-zontal plane, and the cheel being supported in theascending current of air, it relaxed the secondaries ofthe outside wing to obtain an additional steering this relaxation of the outside wing (which wasonly visible for a fraction of a second) was followed byslight extension of the same wing and then relaxationof the inside wing. Thus both wings would acquirethe same disposition. This adjustment would tend tocheck the rotation and to produce speed ahead. Obviously this relaxation of the secondaries of thetwo wings to different extents may be the means em-ployed of producing rapid turns round the dorso-ventralaxis, such as occur when the bird is falling fee
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