AERONAUTICS. 



251 



left, it darts forward in double curve, as shown at fig. 127; 

 the various inclined surfaces made by the wing with the 

 horizon changing at every stage of the stroke. 



At the beginning of the stroke from right to left, the angle 

 made by the under surface of the wing with the horizon {x x) 

 is something like 45° (p), whereas at the middle of the stroke it 

 is reduced to 20° or 25° (q). At the end of the stroke the angle 

 gradually increases to 45° (b), then to 90° (c), after which the 

 wing suddenly turns a somersault (d), and reverses precisely as 

 the natural wing does Sit e,f,g of figs. 67 and 69, p. 141. The 

 artificial wing reverses with amazing facility, and in the most 

 natural manner possible. The angles made by its under 

 surface with the horizon depend chiefly upon the speed with 

 which the wing is urged at different stages of the stroke ; the 

 angle always decreasing as the speed increases, and vice versa. 

 As a consequence, the angle is greatest when the speed is least. 



When the wing reaches the point b its speed is much less 

 than it was at q. The wing is, in fact, preparing to reverse. 

 At c the wing is in the act of reversing (compare c of figs. 84 

 and 85, p. 160), and, as a consequence, its speed is at a 

 minimum, and the angle which it makes with the horizon at 

 a maximum. At d the wing is reversed, its speed being 

 increased, and the angle which it makes with the horizon 

 diminished. "Between the letters d and u the wing darts 

 suddenly up like a kite, and at u it is in a position to com- 

 mence the stroke from left to right, as indicated at u of fig. 

 128, p. 250. The course described and the angles made by 

 the wing with the horizon during the stroke from left to 

 right are represented at fig. 128 (compare with figs. 68 and 

 70, p. 141). The stroke from left to right is in every respect 

 the converse of the stroke from right to left, so that a separate 

 description is unnecessary. 



The Artificial Wave Wing can be driven at any s;peed — 

 it can make its own currents, or utilize existing ones. — The 

 remarkable feature in the artificial wave wing is its adapta- 

 bility. It can be driven slowly, or with astonishing rapidity. 

 It has no dead points. It reverses instantly, and in such a 

 manner as to dissipate neither time nor power. It alternately 

 seizes and evades the air so as to extract the maximum 



