The b'litjhl and Analotiiij of Birds. 43 



communication with the kings. A bit of the wing bone of a goose 

 weighs just half as much as that of a rabbit's leg, of the same 

 length and thickness, even when the marrow has been extracted 

 from the latter. 'I'his lightness of bone greatly facilitates a bird's 

 power of raising itself in the air; but it has also another advantage, 

 that of enabling it to breathe at great heights; this is effected by 

 means of the hollowness of the bones, which causes them to act 

 as pipes for conveying air to the lungs. Another bone which is 

 connected with the flight of a bird is the sternum or breastbone, 

 commonly called the raeny-thought; it keeps the wings at the 

 pro])er distance ajiart while the bird is in the act of flying, and 

 varies in strength proportionally with the power of flight in 

 different birds ; thus in grebes and divers which fly very little, 

 but pass the chief part of their existence on or under water, it is 

 weak and insignificant ; while, on the other hand, in eagles and 

 hawks and birds which pass most of their time in the air, and are 

 strong on the wing, it is proportionally strong and fully developed. 



Of the feathers with reference to flight, little is to be noticed 

 beyond their excessive lightness, the largest quill of a golden 

 eagle weighing only sixty-five grains, and all the feathers of a chicken 

 of thirty-seven ounces being only three ounces; whilst those of the 

 common barn owl weigh scarcely more than one ounce and a half. 

 The downy feathers and the featherings of the quills difler com- 

 pletely in structure: the downy feathers, which act only as a warm 

 covering to a bird, are composed of small fibres completely un- 

 connected with each other; the featherings of the quills on the 

 other hand, which are used as a resistance against the air, are 

 com])osed of fibres which hook on to one another, and form a firm 

 and matted siuface. If this were not so a bird would scarcely be 

 able to fly at all, for when the flat part of the wing was pressed 

 against the air in the act of flight there would be little or no 

 resistance. 



The muscles of a bird's wing are exceedingly large and power- 

 ful, weighing more than all the rest of the muscles of the bodv put 

 together ; this of course is necessary when the exertions of flight 

 are considered, and the rapid motion of the outstretched wing 

 against the resistance of the air. And the force of this resistance 

 is very great as is shown by Bishop Stanley, whom I will quote : 

 "There is one difficulty in the use of wings that anyone may 

 ascertain for himself: let him take the smallest sized boy's kite by 

 the narrow end, and wave it up and down at arm's length, he will 

 instantly perceive how great is the resistance of the air, and how 

 obvious the inability of his muscular strength to produce anything 

 like the rapid motion of a wing. And yet, in order to possess the 

 powers of a bird, he must be able to construct and move artificial 



