AEKONAUTICS. 



247 



suits best is one which is made to act very suddenly and 

 forcibly at the beginning of the down stroke, and which gradu- 

 ally abates in intensity until the end of the down stroke, where 

 it ceases to act in a downward direction. The power is then 

 made to act in an upward direction, and gradually to decrease 

 until the end of the up stroke. The force is thus applied 

 more or less continuously; its energy being increased and 

 diminished according to the position of the wing, and the 

 amount of resistance which it experiences from the air. The 

 flexible and elastic nature of the wave wing, assisted by 

 certain springs to be presently explained, insure a continuous 

 vibration where neither halts nor dead points are observ- 

 able. I obtain the varying power required by a direct piston 

 action, and by working the steam expansively. The power 

 employed is materially assisted, particularly during the up 

 stroke, by the reaction of the air and the elastic struc- 

 tures about to be described. An artificial wing, propelled 

 and regulated by the forces recommended, is in some 

 respects as completely under control as the wing of the 

 insect, bat, or bird. 



Necessity for supplying the Boot of Artificial Wings with 

 Elastic Structures in imitation of the Muscles and Elastic Liga- 

 ments of Flying Animals. — Borelli, Durckheim, and Marey, 

 who advocate the perpendicular vibration of the wing, make 

 no allowance, so far as I am aware, for the wing leaping 

 forward in curves during the down and up strokes. As a con- 

 sequence, the wing is jointed in their models to the frame 

 by a simple joint which moves only in one direction, viz., 

 from above downwards, and vice versa. Observation and 

 experiment have fally satisfied me that an artificial wing, 

 to be effective as an elevator and propeller, onght to be 

 able to move not only in an upward and downward direc- 

 tion, but also in a forward, backward, and oblique direction; 

 nay, more, that it should be free to rotate along its anterior 

 margin in the direction of its length ; in fact, that its move- 

 ments should be universal. Thus it should be able to rise or 

 fall, to advance or retire, to move at any degree of obliquity, 

 and to rotate along its anterior margin. To secure the 

 se\'eral movements referred to I furnish the root of the win^ 



