SEC. Ill EXTERIOR PARTS OF BIRDS 165 



one both long and broad without being pointed is called, is well 

 displayed by such birds as herons, ibises, and cranes ; the flight may 

 be strong and sustained, but is rather slow and heavy. The longest- 

 winged birds are found among the swimmers, particularly the 

 pelagic family of the petrels, and some of the whole-webbed order, 

 as pelicans, particularly the frigate-pelican. The last-named, Tadiy- 

 petes aquilus, has perhaps the longest wings for its bulk of body of 

 any bird whatever, as well as the shortest feet. The American 

 vultures are likewise of great alar expanse in proportion to their 

 weight. The shortest wings, among birds possessing perfect remiges, 

 occur among the lower swimmers, as auks and divers, and among 

 some of the GaUincB. The great auk is, or was, perhaps the only 

 flightless bird with well-formed flight-feathers, only too small to 

 subserve their usual purpose ; though certain South American ducks 

 are said to be in similar predicament. In the penguins, the whole 

 wing -structure is degraded, and the remiges abort in scale -like 

 feathers, the wings being reduced to fins both in form and function. 

 The whole of the existing Ratitos or struthious birds, as the ostrich, 

 cassowary, and emeu, have rudimentary or very imperfect wings, as 

 was the case with the Cretaceous Hesperffrnis ; but the contem- 

 porary of the latter, IchihyorniSi and the still more ancient Archmo- 

 pteryx, appear both to have had excellent ones. 



The disposition of the remiges in their mutual relations is very 

 noteworthy. They have a rigid hollow barrel of great resistant 

 powers, considering the amount of substance,— just like the cylin- 

 drical stem of the cereal plant ; a stout, solid, highly-elastic shaft ; 

 the outer web narrower than the inner, with its barbs set at a more 

 acute angle upon the shaft. Any one of these stiflfer outer vanes 

 overlies the broader and more yielding inner vane of the next outer 

 feather, which, on receiving the impact of air from below, resists as 

 it were with the strength of a second shaft superimposed. Though 

 the " way of an eagle in the air " was a mystery to the wise man of 

 old, the mechanics of ordinary flight are now better understood. 

 But the sailing of some birds for an indefinite length of time, up as 

 well as down, without visible motion of the wings, and without 

 reference to the wind, remains an enigma. The flight of the alba- 

 tross and turkey vulture, I venture to affirm, is not yet explained. 

 The riddle of The Wing will be read when we know how the arch- 

 saurian escaped from ilus to aether. 



The number of true remiges ranges from about sixteen, as in a 

 humming-bird, to upwards of fifty, as in the albatross. Their shape 

 is quite uniform, minor details aside. They are the stiifest, 

 strongest, most perfectly pennaceous of feathers, without evident 

 hyporhachis, if any. They are generally lanceolate, that is, tapering 

 regularly and gradually to an obtuse point, though not infrequently 



