The Matter of Lateral Balance.
"All successful aeroplanes thus far have maintained lateral balance by the principle of changing the angle of incidence of the wings.
"Other ways of maintaining the lateral balance, suggested by observation of the flight of birds are—extending the wing tips and spilling the air through the pinions; or, what is the same thing, varying the area of the wings at their extremities.
"Extending the wing tips seems to be a simple and effective solution of the problem. The tips may be made
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"The elastic wing pinions of a bird bend easily before the wind, permitting the gusts to glance off, but presenting always an even and efficient curvature to the steady currents of the air."