THE EMPIRE OF THE AIK. 403 



Common seuse indicates that the weak can only aspire to light tasks. 

 Which then are the birds that expend the least energy? They are 

 clearly the soaring birds, sweeping over great distances, by the vSole 

 ])Ower of the wind. 



The vultnre's needs are lew, and his strength is moderate. To earn 

 his living he but needs to sight the dead animal from afar. And so 

 what does he know? He knows how to rise, how to float aloft, to 

 sweep the field with keen vision, to sail upon the wind withont effort, 

 till the carcass is seen, and then to descend slowly, after careful recon- 

 naissance and assurance that he m;i>' alight without danger, that he 

 will not be surprised, and compelled to percipitous and painful dejtart- 

 ure. And so he has evolved a peculiar mode of flight; he sails and 

 si)ends no fin-ce, he never hurries, he uses the wind instead of his mus- 

 cles, and the wing Hap occasionally seen is meant to limber u]» rather 

 than to hasten throngh the air. And so the true model to study is the 

 vulture — the great vulture, lieside him the stork is as a wren, the kite 

 a mere butterfly, the falcon a pin feather. 



Whoso has for five minutes had the fortune to see the Oricou vul- 

 ture in full sail through the air, and has not perceived the ])ossibility 

 of his imitation by man, is — I will not say of dull understanding, but 

 certainly inapt to analyze and to appreciate. 



ORNITHOLOGY; SURVEYED IX FLKIHT. 



And here I must deliver a little lecture u^jon ornithology, from a 

 point of view vital to the question, that is to say, tlie acts of flight, — a 

 point of view, (pieerly enough, which is generally ignored in books. 



Flight is the bird's chief peculiarity; it is his one good gift, so let 

 us rai>idly review the acts of the cr(^atures which travel on the air. 



The lowest class is that of the insects. All of them progress by beat- 

 ing flight; they are row^ers {rameurs), save ])erliaps some mid-day butter- 

 flies, which occasionally glirte. Their wings are elastic, true |>lanes, 

 altering their shape and acting on the air through flexible torsion <mi 

 the up and the down stroke. 



Dr. Marey has given very interesting des< ii))tions and grai)iiic dia 

 grams of insect flight. They are ])i(tnred motions, exactly re-^noduced. 

 Xotliing better is to l)e desiicd. 



The reptiles — supposed to be the bird's original prototype— can now 

 adays only produce that little East Indian lizard, the hntco rolaiis, 

 who glides from tree to tiee. He can compass hut a few yards, — sa\ , 

 from one branch to another. 



But i)ast geologic times altord much more interesting sjyecamens. 

 Atthee])och of the Lias, nature i>roduced a \\ln)le family of re]»tiles 

 whose li\('s must Inue been si»ent m tlu' air. The ])ter<»dactyls must, 

 in order to earn their living. ha\e jiossessed t he faculty of mo\ing 

 and sailing on the air. just as the large l)ir<ls do to-day. 



