254 



AERONAUTICS. 



direction, a column of air represented by a, c of fig. 129, p. 

 253.^ The air rushes in from all sides to replace the dis- 

 placed air, as shown at d, e,f, g, i, and so produces a circle 

 of motion indicated by the dotted line s, t, v, w. The wing 

 rises upon the outside of the circle referred to, as more par- 

 ticularly seen at d, e, v, w. The arrows, it will be observed, 

 are all pointing upwards, and as these arrows indicate the 

 direction of the reflex or back current, it is not difficult 

 to comprehend how the air comes indirectly to assist in 

 elevating the wing. A similar current is produced to the 

 right of the figure, as indicated by I, m, o, f, q, r, but seeing 

 the wing is always advancing, this need not be taken into 

 account. 



If fig. 129 be made to assume a horizontal position, in- 

 stead of the oblique position which it at present occupies, 

 the manner in which an artificial current is produced by 

 one sweep of the wing from right to left, and utilized by it 

 in a subsequent sweep from left to right, will be readily 

 understood. The artificial wave wing makes a horizontal 

 sweep from right to left, i.e. it passes from the point a to the 

 point c of fig. 129. During its passage it has displaced a 

 column of air. To fill the void so created, the air rushes in 

 from all sides, viz. from d, e^f^g^li^i ; l,m,OyP,q^T, The 

 currents marked h, i ; p, q, r, represent the reflex or arti- 

 ficial currents. These are the currents which, after a brief 

 interval, force the flame of the candle from right to left. It 

 is those same currents which the wing encounters, and which 

 contribute so powerfully to its elevation, when it sweeps from 

 left to right. The wing, when it rushes from left to right, 

 produces a new series of artificial currents, which are equally 

 powerful in elevating the wing when it passes a second time 

 from right to left, and thus the process of making and 

 utilizing currents goes on so long as the wing is made to 

 oscillate. In waving the artificial wing to and Iro, I found 



1 The artificial currents produced by the wing during its descent may be 

 readily seen by partially filling a chamber with steam, smoke, or some impal- 

 pable white powder, and causing the wing to descend in its midst. By a 

 little practice, the eye will not fail to detect the currents represented at 

 df e,fj g, hj ij I, m, o, p, q, r of fig. 129, p. 253. 



