308 BIRDS. 



CHAPTER XXVI. 



THIRD CLASS OF VERTEBRATE ANIMALS. 

 BIRDS. 



NO department of Nature is left unfurnished with appropriate 

 inhabitants. The inconspicuous air, and those tracts of 

 seeming space too elevated for human ken, are traversed by 

 multitudes of feathered beings, whose buoyancy and beauty are 

 alike the objects of our admiration. The pointed beak, the gently 

 swelling shoulder, the expansive wings, the tapering tail, the light 

 and bony feet of birds, are all wisely calculated to assist and 

 accelerate their passage through the thin and yielding element. 

 Their bodies are covered with a soft and delicate plumage, so 

 disposed as to protect them from the chilly atmosphere through 

 which they pass. Their wings are made of the lightest materials, 

 and yet the force with which they strike the air is so great as to 

 propel their bodies forward with astonishing velocity, whilst the 

 tail serves the purpose of a rudder to direct their flight. Nor is 

 their internal structure less admirably adapted to their mode of 

 life. The framework of their bodies is light and thin, and their 

 muscles equally remarkable for energy and strength. Their blood 

 is hot, and, as it courses through their bodies, imparts intense 

 vitality to every quivering fibre. Their movements are conse- 

 quently rapid and energetic. The falcon cleaves the skies like a 

 thunderbolt, as it stoops upon its quarry, and the swallow and 

 the albatross sweep over geographical degrees in their long-sus- 

 tained peregrinations. The perfection of their respiration is per- 

 haps only second to that of insects : the air they breathe passes, 

 not into their lungs only, but penetrates to the remotest parts of 

 their system, filling their very bones with life, and endowing them 

 with activity and animation adapted to their aerial existence. 



No one can have examined the bony scaffolding of the pelican 

 or the albatross, without being struck with the lightneSs of its 

 proportions, when compared with the dimensions of the full- 

 plumed bird of which it once formed the support a circumstance 

 that has not failed to arrest the attention even of the Muse of 

 Poetry : 



" Their slender skeletons, 

 So delicately framed and half transparent, 

 That I have marvelled how a bird so noble, 

 When in his full magnificent attire, 



