6 SURVEYSOF NATURE. 



become hardly recognizable : efpecially the difference is great be- 

 tween a young bird, and one which has often undergone this 

 operation. 



During this feafon, thofe moil: remarkable for courage become 

 timid, and thofe of weakly conftitutions often die. All ceafe to 

 breed; and their whole nourifliment is abforbed by the uafcent 



plumage, whofe progrefs feems to be as follows,- 



A quill or feather, when come to its full (ize, grows harder as 

 it grows older, and receives a kind of periofleum or Ikin round its 

 Ihaft. In proportion as the quill hardens, its diameter (brinks, 

 its nourifhment decreafes, and it becomes loofe in its focket, till 

 at length it falls. In the mean time, the rudiments of an inci- 

 pient quill are beginning. The ikin forms a little bagj which is 

 fed by a fmall vein and artery, and which daily increafes till pro- 

 truded. While one end vegetates into the beard or vane of the 

 'feather, that attached to the Ikin is foft, and receives a conftant 

 nourifhment, which it difFufes through the whole by the pith. 

 When the quill is full grown, the vein and artery diminifh, and 

 > at length difappear. The quill thus deprived continues in its 

 focket, till after its proper time it flirinks, loofens, and quits its 

 place to a fucceflbr. 



We have feen quadrupeds dwell in fubterranean habitations, 

 in dens, in burrows, or among trees; inhabitants of the air 

 may be expected to choofe a free communication with their pecu- 

 liar element, they decline therefore depth as not to them fecure ; 

 and neftle in the grove, the forefl, or the field, on the ihore, or 

 among rocks, in hopes of concealing their abode from the ey^ of 

 hungry enmity. 



Quadrupeds being viviparous, the male has little opportunity of 

 teflifying his fatisfa(3;ion till the young appear ; but among birds, 

 the male contributes to the advancement of the future progeny ; 

 fometimes by pofitive incubation, fitting on the eggs in the ab- 

 fenee of the female, fometimes by his fong, cheering his confort, 

 and anticipating his endearments, and fometimes by catering tor 

 her while confined in her important occupation. When the 



young 



