CLASS II. 



BIRDS. 



The unjhorn mountains , the barren rocks, and lowly Jhrubs, all raife their joyous fangs ic 

 heaven. — Virgil. 



BIRDS are animals which, for the mofl part, are capable of moving through the 

 air, by the well known action which is called Jlying ; their bodies are covered 

 with feathers, which lap over each other like tiles ; they have two wings, which are 

 likewife covered with feathers, and are adapted, in general, for the purpofes of flying j 

 they have only two legs ; and their jaws are protracted into a naked horny bill, confin- 

 ing of two mandibles. The bodies of birds are exceedingly light in proportion to their 

 fize, when compared with the former clafs ; they are clothed with quills and feathers, 

 inftead of hair ; and are deftitute of external ears, lips, fcrotum, teeth, uterus, bladder, 

 epiglottis,, fornix, corpus caliofum, and diaphragm. The feathers, pennae, are difpofed in 

 alternate rows, thofe of one row being oppofite to the intervals of the next ; this arrange- 

 ment is called quincunx, and they regularly fall over each other in the fame order, like 

 tiles on a roof, imbricatini, each alternate row covering the intervals of the row immedi- 

 ately below ; amid thefe, all over the body, fhort foft woolly downs, plumae, are inter- 

 pofed : All the feathers are convex on their upper, and concave on their under fur- 

 faces ; their external edges, webs, or vanes, are narrow, and their inner vanes are 

 broad ; the rays or laminae of thefe vanes are fofter and lefs connected together to- 

 wards the bafe or fliaft, and thefe, towards the outer end of the feathers, are firmer, 

 more elaftic, and more clofely connected together ; the fliaft of each confifls of a cylin- 

 drical hollow tube, or quill, filled with air, from which a firm, though very light, ftem 

 proceeds to the extremity of the feather, and from this the rays of the vanes ftretch 



E e e 2- out. 



