2 SURVEYS OF NATURE. 



The external fhape of birds, is evidently adapted to pierce 

 through a yielding medium; jharp at firft — gradually fwelliiig 

 — its chief bulk in the middle — and its termination not fudden, 

 but diminifhing — yet, by means of the tail, capable of expanfion : 

 the very confl:ru6lion of a fwift failing veflel! 



The capability of expanlion, or retraction, appears to great 

 advantage in the conftruction of their clothing: is remarkable alfo 

 in their wings and tail, whereby they occupy greater fpace in the 

 fluid wherein they move, without augmenting their weight. A 

 wing, when folded, is in fo clofe union with the creature's body, 

 as to make a part of it; but when expanded, is incomparably be- 

 yond the effedt of oars on a veflel : not only is it generally fpread, 

 but all its parts, not only its joints, but its feathers aflume a 

 new direction, and as fo many radii from the centre of their inler- 

 tion diverge as much as may be, to occupy a greater fpace ; yet 

 never fo much as to leave vacuities between any two. 



Feathers are not merely adapted for flight, by flrength combined 

 with lightnefs, by elaflicity, and by form; but, as defenfative, 

 they proted: their wearer from injury, and, as clothing, they an- 

 fwer every purpofe of warmth and comfort. They generally are 

 uniform in their pofition, are laid all the fame way, one ov^er 

 another, regularly, neatly, fo as to make a perfectly y/woo/Z^ fuper- 

 ficies, whofe external evennefs may prevent fettlings of water, &c. 

 while, next the body, a cherifliing foft down forbids the penetra- 

 tion of cold to injure its wearer. To maintain this Imoothnefs, 

 which, by expofure to accidents, is liable to be deftroyed, the bird 

 has a gland fitiiated on the rump, furniflied with an excretory 

 du£tj this fuppli^ an oil, for the purpofe of drefling the feathers, 

 which the bird communicates to each feather as wanted, by draw- 

 ing it through his bill, in which he has previoufly gathered a 

 quantity. Water-fowl have this oil in the greatefl: abundance, 

 land-fowl have lefs, and thofe domefl:icated very little : Thcle 

 are rarely far from flielter; and nature beftows nothing fuper^ 

 fluous or ufelefs. 



A feather 



