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faced, and guarded with covers and secondary feathers, 

 to keep the air from passing through and so eluding 

 the impulse. 



How admirably wrought are the bones of the wing ! 

 very strong, but light withal; the joints, which open, 

 shut, and move fcvery way, as occasion is, and the 

 various muscles, all suited to the motions which they 

 minister to. 



Next to the parts for flight, let us view the legs and 

 feet which minister to their other motions, both made 

 light for their easier passage through the air, and the. 

 latter, some with membranes for swimming, some 

 without, for steady going, for perching, for catching, 

 and holding their prey, or for hanging by the heels to 

 gather their food : the legs, all curved, for their easy 

 perching or roosting, as also to help them upon their 

 wings in faking their flight. In some, they are long, 

 for wading and searching the waters, in others, if need 

 be, remarkably short. And how wisely are they 

 placed! In all somewhat out of the centre of the 

 body's gravity ; but in such as swim, more than in 

 others, for the better rowing their bodies, as also to 

 help them in diving. 



Geese and Ducks, their bodies being made for swim- 

 ming, have their wings too placed out of the centre of 

 gravity, nearer the head; but the extending the neck 

 and head in tlight, balances the body upon the wings, 

 which is another excellent use (beside searching tor 

 food) of the long necks of these birds. 



But in the Heron, whose head and long neck (al- 

 though tucked up in flight) overbalances the hinder 

 part of the body ; the long legs are extended both to 

 counterpoise the body and to supply what is wanting 

 in the tail. 



ft has been supposed that the flying of birds is ana. 

 logous to the rowing of vessels ; but it is a motion of 

 quite another kind. Oars are struck toward the stern ; 

 whereas birds do not vibrate their wings toward the 

 tail, but waft them downward. Nor does the tail cut 



