46 The FligJit and Anatomy of Birds. 



I cannot conclude these remarks without making mention of 

 three birds whose powers of flight are especially remarkable. The 

 first of these is the albatross (Diomedea exulans). The wings of 

 this huge bird measure, when spread, as much as fourteen feet ; 

 on land it is almost entirely helpless, and may easily be killed with 

 a stick, for their length of wing prevents them from rising off the 

 ground, unless they can launch themselves from off a projecting 

 ledge of rock or precipice. The albatross may be called the king 

 of sea-birds ; it passes most of its time in the air, where it soars 

 up to immense heights, and is exceedingly powerful on the 

 wing. 



The second is the tropic bird (Phaeton Phsenicurus). This 

 bird which is small and light has, like the swift, wings exceedingly 

 long in proportion to the size of its body ; it passes most of its 

 time in the air, only coming to land when in need of rest; like the 

 albatross, it is ahuost heljiless on land, whilst in the air its motions 

 are exceedingly rapid and graceful. 



The last bird I will mention is the Frigate-bird (Tachypetes 

 Aqnila), and this is by far the most wonderful of them all. Its 

 wings measure on an average twelve feet from tip to tip, whilst its 

 thigh bone is but a single inch in length. The powers of flight in 

 this bird are so extraordinary that it never comes to land at all 

 except in the breeding season, and what is still more wonderful, is 

 never seen to swim or repose on the water ; Not only can this 

 bird fly with wondrous rapidity and gracefulness, but it is even 

 able to sleep in the regions of the air without risk of falling. I 

 will quote Bishop Stanley's explanation of this apparent impossi- 

 bility : he says, "On examining it, we shall find just beneath the 

 throat a large pouch communicating with the lungs, and with the 

 hollow and peculiarly light bone-work of its skeleton. Suppose, 

 then, that the bird wishes to rest in the air, in the first place it 

 avails itself of its large wings, which it is enabled by long practice 

 to keep expanded, and which are in themselves nearly sufiicient 

 to- sustain its weight and float its light body in the air. But in 

 addition to the wing, suppose the bird fills its large pouch with 

 air, and from thence forces it into all its bones and cavities between 

 the flesh and skin, what will happen ? That the heat of its circu- 

 lation (and it is well known that the heat of a bird's circulation is 

 considerably beyond that of other animals) will rarefy the internal 

 air, which will therefore puff" up not only the pouch, but every 

 cavity, and thus give the bird a surprising additional buoyancy or 

 power of floating, even in the higher regions of the atmosphere. 

 And that this is the case may be presumed from its habits; for when 

 the lower currents of the air are stormy and disagreeable, up goes 

 the Frigate-bird to a higher and calmer current, where, just as we 



