252 



AfiflONAUTICS. 



of support with the minimum of slip, and the minimum 

 of force. It supplies a degree of buoying and propelling 

 power which is truly remarkable. Its buoying area is 

 nearly equal to half a circle. It can act upon still air, 

 and it can create and utilize its own currents. I proved this 

 in the following manner. I caused the wing to make a 

 horizontal sweep from right to left over a candle ; the wing 

 rose steadily as a kite would, and after a brief interval, the 

 flame of the candle was persistently blown from right to left. 

 I then waited until the flame of the candle assumed its 

 normal perpendicular position, after which I caused the wing 

 to make another and opposite sweep from left to right. The 

 wing again rose kite fashion, and the flame was a second time 

 affected, being blown in this case from left to right. I now 

 caused the wing to vibrate steadily and rapidly above the 

 candle, with this curious result, that the flame did not incline 

 alternately from right to left and from left to right. On the 

 contrary, it was blown steadily away from me, i.e, in the 

 direction of the tip of the wing, thus showing that the arti- 

 ficial currents made by the wing, met and neutralized each 

 other always at mid stroke. I also found that under these 

 circumstances the buoying power of the wing was remarkably 

 increased. 



Compound rotation of the Artificial Wave JVing : the different 

 farts of the Wing travel at different speeds. — The artificial 

 wave wing, like the natural wing, revolves upon two centres 

 {ah, cd of fig. 80, p. 149; fig. 83, p. 158, and fig. 122, 

 p. 239), and owes much of its elevating and propelling, 

 seizing, and disentangling power to its diff'ererit portions 

 travelling at diff*erent rates of speed (see fig. 56, p. 120), and 

 to its storing up and giving ofl" energy as it hastens to and 

 fro. Thus the tip of the wing moves through a very much 

 greater space in a given time than the root, and so also of the 

 posterior margin as compared with the anterior. This is 

 readily understood by bearing in raind that the root of the 

 wing forms the centre or axis of rotation for the tip, while 

 the anterior margin is the centre or axis of rotation for the 

 posterior margin. The momentum, moreover, acquired by 

 the wing during the stroke from right to left is expended in 



