THE EMPIRE OF THE AIR. 



441 



aliuht without hrojikiiij;' their leg-s. It is <'U'ai' however that tkey are 

 lianipered by this excess ofsiirtace; not one of them is remarkable as 

 a Hyer, neither as to velocity — which is easily ex|)laiiie(l, noi- even as a 

 permanent denizen of the air — which is more extiaordinary. 



They are in foct so well eqniitjsed for sailing,' on li<>'ht winds that the 

 surlace resistance destroys all the other qnalities when the breeze 

 fresliens. It is only when the weight becomes 4 ponnds or more that 

 tlie mass momentum succeeds in overcoming the fri(;tion of the air 

 against these over-feathered wings. 



The birds first named in the table Hy as unsteadily as the butterfly; 

 the hoopoe, the armed plover, and the laj^wiug can advance against 

 strong winds only by comj)letely folding- their wings. This deflciency 

 diminishes with the increase in weight. The ibis flies better than the 

 small heron, and both are distanced bv the storks. 



Kui. <i. — TliK urcy Horon. 



We tind proof in this type tluit the useful, active surface of the wing 

 lies in the hand and the forearm, and that the arm remains almost 

 quiescent in flapping. The demonstration is i)al]table, as is ever the 

 case in nature. The feathers of the humerus have been simply sup- 

 pressed in most of the herons, and only those of the covert remain, 

 which latter feathers aic merely ornamental. 



Tite Ix-cslrcJ Falcon. — The kestrel is common in France. It inhabits 

 our large cities. It is known by all observers, and they doubtk'ss have 

 gathered their best knowledge from its evolutions. Its strength is great 

 and it always rows when hunting; but when there comes a change of 

 weather and the soutli wind sets in, then the creature climbs u|) soaring 

 into the sky and exhibits its talents as a sailing bird, which talents are 

 fully as great as might be expected from its mass. 



The peregrine Falcon. — A rare bird, and therefore dillicult to study. 

 An astonishing rower, reaching at times a velocity almost unique; the 

 IjigeoUj the duck are then greatly out-distanced. - - - 



