420 DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



may, I think, be demonstrated in a variety of ways. If a rigid rod be made to 

 vibrate by the hand the vibration is not smooth and continuous ; on the con- 

 trary, it is irregular and jerky, and characterised by two halts or pauses (dead 

 points), the one occurring at the end of the up stroke, the other at the end 

 of the down stroke. This mechanical impediment is followed by serious con- 

 sequences as far as power and speed are concerned — the slowing of the wing at 

 the end of the down and up strokes involving a great expenditure of power and a 

 disastrous waste of time. The wing, to be effective as an elevating and pro- 

 pelling organ, should have no dead points, and should be characterised by a 

 rapid winnowing or fanning motion. It should reverse and reciprocate with 

 the utmost steadiness and smoothness — in fact, the motions should appear as 

 continuous as those of a fly-wheel in rapid motion : they are so in the insect. 



To obviate the difficulty in question, it is necessary, in my opinion, to employ 

 a tapering elastic rod or series of rods bound together for the anterior margin 

 of the wing. 



If a longitudinal section of bamboo cane, 10 feet in length, and 1 inch in 

 breadth (vide fig. 57, p. 421), be taken by the extremity and made to vibrate, it 

 will be found that a wavy serpentine motion is produced, the waves being greatest 

 when the vibration is slowest (fig. 58, p. 421), and least when it is most rapid (fig. 

 59, p. 421). It will further be found that at the extremity of the section where 

 the impulse is communicated there is a steady reciprocating movement devoid of 

 dead points. The continuous movement in question is no doubt due to the fact 

 that the different portions of the reed reverse at different periods — the undula- 

 tions induced being to an interrupted or vibratory movement very much what 

 the continuous play of a fly-wheel is to a rotatory motion. 



The Wave Wing of the Author. — If a similar reed has added to it, tapering 

 rods of whalebone, which radiate in an outward direction to the extent of a foot 

 or so, and the whalebones be covered by a thin sheet of india-rubber, an artificial 

 wing, resembling the natural one in all its essential points, is at once produced 

 (vide fig. 60, p. 421). I propose to designate this wing, from the peculiarities of 

 its movements, the ivave wing (fig. 61, p. 421). If the wing referred to (fig. 61) 

 be made to vibrate at its root, a series of longitudinal (c d e) and transverse 

 (f g h) waves are at once produced, the one series running in the direction of 

 the length of the iving, the other in the direction of its breadth (vide p. 330). 

 This wing further tivists and untivists, figure of 8 fashion, during the down and 

 up strokes, as shown at figure 62, page 423 (compare with figure 2, p. 336). 

 There is, moreover, a continuous play of the wing, the clown stroke gliding 

 into the up one, and vice versa, which clearly shows that the down and up 

 strokes are parts of one whole, and that neither is perfect without the other. 



This wing is endowed with the very remarkable property that it will fly in 

 any direction, demonstrating more or less clearly that flight is essentially a pro- 



