180 BIRDS IN GENERAL. 



feathers, all lying one way, and at once answering the 

 purpose of warmth, speed, and security : they mostly 

 tend backward, and are laid over one another in an ex- 

 act and regular order, armed with warm and soft down 

 next the body, and more strongly fortified and curi- 

 ously closed externally, to fence off the injuries of the 

 weather : but, lest these feathers should spoil by their 

 violent attrition against the air, or imbibe the moisture 

 of the atmosphere, the animal is furnished with a gland 

 behind containing a proper quantity of oil, which can 

 be pressed out by the bill of the bird, and with which 

 it carefully anoints the injured feathers. 



In all birds, except nocturnal ones, the head is smaller: 

 and bears less proportion to the body than in quadru- 

 peds, that it may more easily divide the air in flying, 

 and make way for the body so as to render its passage 

 more easy : their eyes also are more flat and depressed, 

 though they are much more calculated for distant vi- 

 sion than any part of the brute creation ; and they are 

 capable of discerning things at a distance, which are 

 absolutely impenetrable to the human sight. All birds 

 are destitute of an external ear, though all are furnished 

 with holes which convey different sounds into the au- 

 ditory canal ; and the extreme delicacy and quickness 

 of this organ is proved by the ease and facility with 

 which they either acquire a tune, or pronounce words 

 frequently repeated in their presence. If the eye of 

 these animals is peculiarly calculated for distant per- 

 ception, and the ear for accurate sound, their wings 

 are no less admirably formed for the purpose of aiding 

 and assisting their flight. In order to move these con- 

 ductors with ease and facility, all birds are furnished 

 with two very strong pectoral muscles, which lie on 

 each side the breast-bone, and by means of these a. 



