154 



ANIMAL LOCOMOTION. 



These results are further secured by the undulatory or waved 

 track described by the wing during the down and up 

 strokes. It is a somewhat remarkable circumstance that 

 the wing, when not actually engaged as a propeller and eleva- 

 tor, acts as a sustainer after the manner of a parachute. This 

 it can readily do, alike from its form and the mode of its 

 application, the double curve or spiral into which it is thrown 

 in action enabling it to lay hold of the air with avidity, in 

 whatever direction it is urged. I say " in whatever direction," 

 because, even when it is being recovered or drawn off the 

 wind during the back stroke, it is climbing a gradient which 

 arches above the body to be elevated, and so prevents it from 

 falling. It is difficult to conceive a more admirable, simple, 

 or effective arrangement, or one which would more thoroughly 

 economize power. Indeed, a study of the spiral configuration 

 of the wing, and its spiral, flail-like, lashing movements, in- 

 volves some of the most profound problems in mathematics, 

 — the curves formed by the pinion as a pinion anatomically, 

 and by the pinion in action, or physiologically, being exceed- 

 ingly elegant and infinitely varied; these running into each 

 other, and merging and blending, to consummate the triple 

 function of elevating, propelling, and sustaining. 



Other differences might be pointed out ; but the foregoing 

 embrace the more fundamental and striking. Enough, more- 

 over, has probably been said to show that it is to wing- 

 structures and wing-movements the aeronaut must direct his 

 attention, if he would learn " the way of an eagle in the air," 

 and if he would rise upon the whirlwind in accordance with 

 natural laws. 



The Wing at all times thoroughly under control— The wing 

 is moveable in all parts, and can be wielded intelligently 

 even to its extremity; a circumstance which enables the 

 insect, bat, and bird to rise upon the air and tread it as a 

 master — to subjugate it in fact. The wing, no doubt, abstracts 

 an upward and onward recoil from the air, but in doing this 

 it exercises a selective and controlling power ; it seizes one 

 current, evades another, and creates a third ; it feels and 

 paws the air as a quadruped would feel and paw a treacherous 

 yielding surface. It is not difficult to comprehend why this 



