If a longitudinal section of bamboo cane, ten feet in length, and one inch in breadth (fig. [117]), be taken by the extremity and made to vibrate, it will be found that a wavy serpentine motion is produced, the waves being greatest when the vibration is slowest (fig. 118), and least when it is most rapid (fig. 119). It will further be found that at the extremity of the cane where the impulse is communicated there is a steady reciprocating movement devoid of dead points. The continuous movement in question is no doubt due to the fact that the different portions of the cane reverse at different periods—the undulations induced being to an interrupted or vibratory movement very much what the continuous play of a fly-wheel is to a rotatory motion.
The Wave Wing of the Author.—If a similar cane has added to it, tapering rods of whalebone, which radiate in an outward direction to the extent of a foot or so, and the whalebones be covered by a thin sheet of india-rubber, an artificial wing, resembling the natural one in all its essential points, is at once produced (fig. [120]). I propose to designate this wing, from the peculiarities of its movements, the wave wing (fig. [121]). If the wing referred to (fig. 121) be made to vibrate at its root, a series of longitudinal (c d e) and transverse (f g h) waves are at once produced; the one series running in the direction of the length of the wing, the other in the direction of its breadth (vide p. [148]). This wing further twists and untwists, figure-of-8 fashion, during the up and down strokes, as shown at fig. [122], p. 239 (compare with figs. [82] and 83, p. 158; fig. [86], p. 161; and fig. [103], p. 186). There is, moreover, a continuous play of the wing; the down stroke gliding into the up one, and vice versâ, which clearly shows that the down and up strokes are parts of one whole, and that neither is perfect without the other.
Fig. 117.
Fig. 117.—Represents a longitudinal section of bamboo cane ten feet long, and one inch wide.—Original.
Fig. 118.
Fig. 118.—The appearance presented by the same cane when made to vibrate by the hand. The cane vibrates on either side of a given line (x x), and appears as if it were in two places at the same time, viz., c and f, g and d, e and h. It is thus during its vibration thrown into figures-of-8 or opposite curves.—Original.