AERONAUTICS. 



245 



gearing apparatus is avoided, and the number of joints and 

 working points reduced — a matter of no small importance 

 when it is desirable to conserve the motor power and keep 

 down the weight. 



How to apply Artificial Wings to the Air, — Borelli, 

 Durckheim, Marey, and all the writers with whom I am 

 acquainted, assert that the wing should be made to vibrate 

 vertically. I believe that if the wing be in one piece it 

 should be made to vibrate oUiquely and more or less horizon- 

 tally. If, however, the wing be made to vibrate vertically, 

 it is necessary to supply it with a ball-and-socket joint, and 

 with springs at its root {m n of fig. 125, p. 241), to enable it 

 to leap forward in a curve when it descends, and in another 

 and opposite curve when it ascends {vide a, c, e, g, i of fig. 81, 

 p. 157). This arrangement practically converts the vertical 

 vibration into an oblique one. If this plan be not adopted, 

 the wing is apt to foul at its tip. In applying the wing to 

 the air it ought to have a figure-of-8 movement communicated 

 to it either directly or indirectly. It is a peculiarity of the 

 artificial wing properly constructed (as it is of the natural 

 wing), that it twists and untwists and makes figitre-of-S curves 

 during its action (see ah, cd of fig. 122, p. 239), this enabling 

 it to seize and let go the air with wonderful rapidity, and 

 in such a manner as to avoid dead points. If the wing be 

 in several pieces, it may be made to vibrate more vertically 

 than a wdng in one piece, from the fact that the outer half 

 of the pinion moves forwards and backwards when the wing 

 ascends and descends so as alternately to become a short and 

 a long lever ; this arrangement permitting the wing to avoid 

 the resistance experienced from the air during the up stroke, 

 while it vigorously seizes the air during the down stroke. 



If the body of a flying animal be in a horizontal position, 

 a wing attached to it in such a manner that its under surface 

 shall look forwards, and make an upward angle of 45° with 

 the horizon is in a position to be applied either vertically 

 (figs. 82 and 83, p. 158), or horizontally (figs. 67, 68, 69, and 

 70, p. 141). Such, moreover, is the conformation of the 

 shoulder- joint in insects, bats, and birds, that the wing can 

 be applied vertically, horizontally, or at any degree of obliquity 



