riir: kmpium: ok tiie air. 



40: 



The tail lo be effective I'ciiiiiics that tin- speed. <>r tlic wind, siiall 

 be great (these are e(|uiA;deiit in aviatioji), Ibi' il the Inrd liad no other 

 means of steering, his movements would be dreadtiill> liaiii|tered at 



Kp;. 1. — lVli.;iii ill riiiilit. 



loAY Speeds. He substitutes, as we sludl see, ibi' this impeiieet action 

 otlier and more energetic means of clianging Ins diit^ction. 



Tlie JiUjht <tf the Jidpp'nKj hinis. — Let us view tli<' biid when lirst he 

 means to start. He is on the grcaind: he croucluvs to sjaing up. letting 

 ]iis wings liang <h)wn h»ose]y. 



Let us analyze this tirst movement. The wing is divided into three 

 planes, one formed by the liumerus. another by the radius and tlu^ 

 ulna, and the third by the hand. The result produced by the ])osition 

 of these three planes is to otilei- no resistane<' to the air. 



But tliisdoes not exhaust the decom[)osition of this attitude: all the 

 feathers, }>articularly those at the rips of the w ings, are so incline'-^ tliat 

 the air is met by their edges instead of their broadsides. Still further 

 we see that the wing is never raised on the ujt stroke at full S])i-ead, l>ut 

 well folded on itself, so as to present the least possible surfac*' and yet 

 ac^eomplish the movement with least i^lilbrt and greatest celerity. 



Xow let us note the seconrl mo\-ement : the bird's wing beating down 

 the air. The action is simple; the wing is fully extend<'<l and ^titf. the 

 feathers close its whole surface, and it is concaNc on the nnder side. 

 There is therefore a, great difference in the result obtained between the 

 lip and down stioke of the wing. This dilfereiice ]»i(»duces the lifting 

 effe(;t in tla])i)ing tlight. 



Exactly to apju'eeiate this dilfei-ence, to feel it as it were, let the reader 

 take the freshly severed wing of a large bird, grasp it b\ the humerus, 

 and imitate the up and down stroke. This exitei-iment will give a bet- 

 ter understanding of beating Might than all i)ossiblc descaiptions and 

 explanations. It is proximate and plain, one feels the efforts reipiired 

 by each nu)vemeiit, and ]»asses judgment on them directly. The upward 

 spring of tlie legs, and the tirst Ijeat of the wings, have launched the 

 bird in the air. He rejx'ats the beats rapidl>' and rises, n(»t vertically, 

 but at ail angle within lo". To rise jierpendicularly the bird is com- 



