A H /STORY OF 



oars ; from whence the poets have adopted 

 ihe metaphor of remigium alarutn, when they 

 described the wavy motion of a bird in flight. 



What we are called upon next to admire 

 in the external formation of birds is, the neat 

 position of the feathers, lying all one way, 

 answering at once the purposes of warmth, 

 speed, and security. They mostly tend back- 

 ward, 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 curiously closed externally, to 

 fence off the injuries of the weather. But, 

 lest the feathers should spoil by their violent 

 attrition against the air, or imbibe the mois- 

 ture of the atmosphere, the animal is fur- 

 nished with a gland behind, containing a pro- 

 per quantity of oil, which can be pressed out 

 by the bird's bill, and laid smoothly over 

 every feather that wants to be dressed for the 

 occasion. This gland is situated on the rump, 

 and furnished with an opening or excretory 

 duct ; about which grows a small tuft of fea- 

 thers somewhat like a painter's pencil. When, 

 therefore, the feathers are shattered or rum- 

 pled, the bird, turning its head backwards, 

 with the bill catches hold of the gland, and, 

 pressing it, forces out the oily substance, with 

 which it anoints the ^disjoined parts of the fea- 

 thers ; and drawing them out with great assi- 

 duity, recomposes and places them in due 

 order ; by which they unite more closely to- 

 gether. Such poultry, however, as live for 

 the most part under cover, are not furnished 

 with so large a stock of this fluid, as those 

 birds that reside in the open air. The fea- 

 thers of a hen, for instance, are pervious to 

 every shower ; on the contrary, swans, geese, 

 ducks, and all such as Nature has directed 

 to live upon the water, have their feathers 

 dressed with oil from the very first day of 

 their leaving the shell. Thus their stock of 

 fluid is equal to the necessity of its consump- 

 tion. Their very flesh contracts a flavour 

 from it, which renders it in some so very ran- 

 cid, as to make it utterly unfit for food ; how- 

 ever, though it injures the flesh, it improves 

 the feathers for all the domestic purposes to 

 which they are usually converted. 



Nor are the feathers with which birds are 

 covered less an object of admiration. The 

 shaft of every feather is made proportionably 

 strong ; but hollow below for strength and 

 lightness, and above filled with a pith to feed 

 the growth of the vane or beard that springs 

 from the shaft of the feather on either side. 

 All the feathers are placed generally ac- 

 cording to their length and strength, so that 

 the largest and strongest feathers in flight 

 have the greatest share of duty. The vane 

 or beard of the feather is formed with equal 

 contrivance and care. It consists not of one 



continued membrane ; because, if this wore 

 broken, it could not easily be repaired; but it 

 is composed of many layers, each somewhat 

 in itself resembling a feather, and lying 

 against each other in close conjunction. To- 

 wards the shaft of the feather, these layers 

 are broad, and of a semicircular form, to serve 

 for strength, and for the closer grafting them 

 one against the other when in action. To- 

 wards the outer part of the vane, these layers 

 grow slender and taper, to be more light. 

 On their under-side they are thin and smooth, 

 but their upper outer-edge is parted into two 

 hairy edges, each side having a different sort 

 of hairs, broad at bottom, and slender and 

 bearded above. By this mechanism, the 

 hooked beards of one layer always lie next 

 the straight beards of the next, and by that 

 means lock and hold each other. 1 



1 All birds are covered with feathers, and they are 

 the only animals which, properly speaking, are so. 

 These feathers are of two sorts feathers for clothing, to 

 protect the animal from the vicissitudes of the weather, 

 and feathers for flight. Both of these are beautifully 

 modified, so as to suit the different habits of the several 

 species, and adapt them to the climates and the ele- 

 ments in which they find their food. 



Some other animals, as for instance the lepidopterous 

 insects the butterflies and the moths have a coat of 

 feathers, or rather of fringed or feathery scales ; but 

 these have few or none of the characters of true feathers, 

 and in no case, except that of birds, are feathers the in- 

 struments of flight. But still we can, in the imperfect 

 feathers of the lepidoptera, discover one of the uses of 

 feathers in birds better than we can perhaps do in the 

 feathers of birds themselves, as in them it is conjoined 

 with other uses. The study of one animal often assists 

 us in acquiring a knowledge of another, especially when 

 the one contains a single part of that which is a com- 

 pound organ in another ; because by this means we get 

 an analysis of the living animal, which is far more satis- 

 factory than any that we could obtain by the dissection 

 of a dead one ; for we can, in the one case, actually see 

 the part of the organ in action, whereas in the other we 

 can only infer or guess at the way in which it acts. 



Now, every one must have noticed, that bees, flies, 

 and all insects which have membranous or naked wings, 

 must keep those wings constantly in rapid motion while 

 they fly. The motion is often so rapid that the wings 

 cannot be seen, any further than by a sort of tremulous 

 motion in the air; and the action of the wings produces 

 all that humming and buzzing among flying insects 

 which makes the summer air so lively; for insects do 

 not breathe by the mouth, and have no organ of voice of 

 any description. The action of those naked wings upon 

 the air must be very considerable; because, when a 

 common bluebottle-fly (Musca vomitoria) alights on the 

 window, and marches along one of the dusty bars of the 

 frame, winnowing the air with its wings, in a vain at- 

 tempt to escape through the glass, it stirs the dust more 

 in proportion than a coach and six driving rapidly along 

 a dry road on a hot summer's day. Insects with wings 

 of this description cannot hover, or lean on the air with 

 still and expanded wing. 



But the lepidoptera, especially the butterflies, do ho- 

 ver about, and rest on the air, and wheel in various di- 

 rections, with very little apparent motion of the wings; 

 and when they do move them, it is done much mote 

 slowly than the motion of the naked wing, in proportion 

 to the rate of progressive motion. These lepidopti rous 



