270 ORNITHOLOGY. 



covering of the body. The bone of the upper arm (humerus, I.) 

 gives rise to another series of feathers, called tertiaries, which, 

 in such birds as the Plovers, Curlew, etc., .are greatly lengthened ; 

 but in their structure are yet weaker than the secondaries. 

 Fastened to the little bone which represents the thumb, are two or 

 three short and stiff feathers, called the winglel, (or bastard-wing ;) 

 they lie upon the base of the first primaries, at the edge of the 

 wing. Corresponding with the series of feathers, there are both 

 on the outer and inner surface of the wing, several rows of 

 smaller ones, called coverts, from their office of protecting the 

 basal part of the quills; the feathers covering the shoulder-blade, 

 or scapula, are called scapulars. 



If we examine each feather separately, we find it composed of 

 two parts ; (1) a light but firm shaft, hollowed below for strength 

 and lightness, into a horny tube, containing the blood-ves- 

 sels by which it is sustained ; (2) the vane, or beard of the 

 feather, composed of a double series of layers, or thin parallel 

 plates on each side of the shaft, and set at an angle to it. Towards 

 the shaft of the feather, these layers are broad, and of a semi-cir- 

 cular form, to serve for strength, and for the closer grafting them 

 one against the other, when in action. Towards the outer part 

 of the vane, the layers grow slender and taper, to be more light. 

 On their wider side, they are thin and smooth ; but their upper 

 outer edgs is parted into two hairy edges, each side having a dif- 

 ferent set of hairs, broad at the bottom, and slender and bearded 

 above. By this means, the hooked beards of one layer always 

 lie next the straight beards oC.the next, and lock and hold each 

 other. No resistance is offer^l to the flight of birds by this ar- 

 rangement; while beneath thes^Jkere is a layer of soft down, 

 which preserves them from coldBjfthe effects of which, but for 

 this provision, they would have beenNmuch exposed. 



The wings are usually placed at that part of the body which 

 serves to poise the whole and to support it. The feathers oftfie 

 wing overlap each other, and present a continuous surface of 

 great breadth, by repeated strokes of which upon the air, the bird 

 performs its flight. (Plate X. fig. 2.) 



"Each feather is concave, whether we regard it transversely 

 or longitudinally ; its stem, or middle, is remarkably strong, 

 though very light, and the beards which present their edges in 

 the direction of the stroke, are linked to each other by a series of 

 minute hooks." These arrangements add to the power of the 

 wings in their downward strokes upon the air. 



Every part of a bird, except the beak and the lower, or poste- 

 rior extremities, is, in general, clothed with feathers. Tne feet 



