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AUGUST, 1876. 



THE FLIGHT OF BIRDS. 



T^T^HAT a wonderful endowment is the 



' ' power of flight ! And how graceful- 

 ly and advantageously do birds employ it 

 as their means of locomotion ! Naturalists 

 rarely fail to direct their attention to the 

 flight of birds, as it is a point of great in- 

 terest, and one which has given rise to va- 

 rious theories as to the reason why, by 



forcing the wings through space, birds are 

 enabled to propell themselves. At first, 

 one would be led to remark that the same 

 dii'ection of force exerted by the arms of a 

 swimmer, is applicable generally speaking, 

 to the wings of a bird. This is true as far 

 as the doctrine of motion is concerned, rel- 

 ative to the locomotion in general of these 

 bodies, but the elements in which they are 

 employed, being entirely different in nature 

 and consistency, require a correspondent 

 change in the point of tendency of action, 

 and this change is rendered more distinct 

 by a consideration of the structure of the 

 bodies which generate the motion, i. e., the 

 wings of the bird and the arms of the swim- 

 mer. In the first place, the former have 

 to sustain the greater weight of the object, 

 in proportion to the character of the ele- 

 ment than the latter, thus demanding a 

 downward exertion as well as backward, to 

 both support and propell the bird. An ex- 

 planation of the modus operandi is given in 

 Scribner's Monthly, which is as applicable 

 as any probably given. It is written by 

 the Duke of Argyle. He says that the 

 open wing forms a hollow on its under side ; 

 when the wing is forced down, the pressure 

 of the air is caught under this concavity, 

 lifting the bird up, in the same manner as 

 one would hoist himself up between the 

 parallel bars of a gymnasium. This is the 

 explanation of the manner in which the bird 

 supports itself, but this motion alone would 

 not tend to produce any progress forward, 

 were it not for the structure of the Aving. 

 The front edge, being formed of the un- 

 yielding muscles and bones of the fore-arm, 

 resists, while the after portion, of the flex- 

 ible and soft ends of the feathers, readily 

 yields to, the air. Now, when the wing 

 is forced down, the air underat, finding the 

 feathers yielding the easier, rushes out 

 there, and in so doing, bends up the flexi- 

 ble ends of the quills, pushing them for- 

 ward out of the way, which, of course, has 

 a tendency to propell the bird forward. 

 This process rapidly repeated, results in 

 the phenomenon of flight. 



Like most other hypotheses of cause and 



