276 FACULTIES OF BIRDS. 



frame is altered and made light, in a manner con- 

 sistent with strength. We see, also, how the mech- 

 anism of the anterior extremity is changed, and the 

 muscles of the trunk differently directed."* 



Though it is obvious that birds could not fly with- 

 out wings, yet the peculiar mechanism of the pro- 

 cess is not, we believe, generally understood. It is 

 no uncommon thing to see a goose, while walking 

 on the common, spread out its wings to their full 

 extent, and begin to flap them about with great vio- 

 lence, and yet the bird is not thereby moved an inch 

 from the ground ; a circumstance that, without in- 

 quiry into the cause, seems contrary to what might 

 have been anticipated. By observing the difference 

 between this ground-flying (if we may call it so) of 

 the goose, and the actual rising of a pheasant, for 

 example, into the air, we may arrive at the reason 

 why the goose does not, while the pheasant does, 

 ascend. The goose, it may be remarked, keeps her 

 wings spread both in the upward and the down- 

 ward motion, and, consequently, the resistance of 

 the air in the first case will press her body down- 

 ward rather than upward ; while, as her evident in- 

 tention is not to rise above the ground, she forcibly 

 expels the air from her aircells, as may be infer- 

 red from the screaming always uttered on those 

 occasions, and caused, we have reason to believe, 

 by the forcible expulsion of the air. Her body is 

 thus rendered specifically heavier, and, consequent- 

 ly, resists the upward impulse given by the down- 

 ward motion of the wings. The pheasant, on the 

 other hand, instead of expelling the air, takes a deep 

 inspiration, increasing the size of the body as much 

 as possible, inflating at the same time the wing-feath- 

 ers, and bulging them outward without separating 

 their tips from the sides. While taking deep inspi- 

 rations, he may be observed, also, several times 



* Bridgewater Treatise on the Hand, p. 77. 



