106 that' 



absent, are plumes. In many 

 feathers, at the point where the 

 horny tube, 16, commences, a 

 smaller shaft, furnished with 

 barbs, appears. This is called 

 the plumule, 17. Besides the 

 true feathers, the skin of many 

 birds, especially those of aquatic 

 habits, is covered with down. 

 20 These down feathers, 



/O'i^lt^N a great number of 

 \ |; feathery branches 

 ' / i \10S^> springing immediate- 

 w5jf ^ ly from the quill, and 

 I without a central 

 385. 5 / ia ^. 



The habits of flight of birds 

 are materially influenced by the 

 shapes of their wings and tails. 

 With fishes their tails, 341, are 

 the organs of propulsion, the 

 fins, 340, being used to, guide 

 and steady the body ; but the 

 tails of birds are useless for pro- 

 pulsion, and are used merely for 

 guidance, motion being acquired 

 solely by the action of the wings. 



Birds of the swallow tribe, 1, 

 are remarkable for the rapidity 



2 



386. 



and suddenness of their move- 

 ments. In their wings we find 

 that the primaries, 2, are largely 

 developed ; the other feathers are 



*S IT; 



very small ; their wings are 

 pointed, firm, and smooth, and 

 well calculated for striking the 

 air with effect. Wings of this 

 form are essential to rapid aerial 

 motion. Their under surfaces 

 are usually flat, and calculated 

 for rapid straightforward flight. 

 Birds with wings thus formed 

 find it difficult to rise quickly in 

 the air. The falcon, 3, contrives 

 to soar by flying in a circle, or 

 by directing his course against 

 the wind, presenting his breast 

 and wings obliquely to the aerial 

 current, and rising as a kite does. 



3 



387. 



The wings of eagles are concave 

 3-382 ; hence they soar with 

 greater ease. The wings of owls 

 consist of a large proportion of 

 soft feathers, and their whole 

 plumage is full and downy ; the 

 softness of their wing-feathers 

 renders their flight noiseless, 

 feeble, and wheeling. jk 



The tails of birds present 

 greater diversity of form than 

 their wings. Birds whose tails 

 are deficient do not possess the 

 power of steering themselves : 

 this is the case with the king- 

 fisher, B. Their flight, there- 

 fore, consists of a series of 

 straight darts, extending only to 



