the peculiar exterior covering of birds, constituting what is called their plumage. Feathers vary in size, form, colour, and function, in different species, in the several parts of the same individual, and also in the same bird at different stages of its existence; and their exquisite adaptation to the several ends they are designed to serve has often been adduced as illustrative of creative wisdom. "The covering of birds," says Paley, "cannot escape the most vulgar observation: its lightness, its smoothness, its warmth, the disposition of the feathers all inclined backward, the down about their stem, the overlapping of their tips, their different configuration in different parts, not to mention the variety of their colours, constitute a vestment for the body, so beautiful and so appropriate to the life which the animal is to lead, as that we should have no conception of anything equally perfect if we had never seen it, or can now imagine anything more so."

Feathers, when analyzed chemically, seem to possess nearly the same properties with the hair of mammifers and the scales of reptiles; but they differ essentially from the integuments of these classes of animals in respect to mechanical structure—being much more complex in their constituent parts. The principal parts of an ordinary feather are the tube or quill, the shaft or stem, and the vane. The quill is a hollow semi-transparent cylinder composed of coagulated albumen, and is more or less protracted. It closely resembles a thin piece of clear horn, both in appearance and chemical constitution; while at the same time it combines, in an eminent degree, the opposite qualities of strength and lightness. The horny substance of the quill in many species is disposed internally in longitudinal fibres, while the outer part is composed of transverse or annular fibres. Hence the reason why, in making a pen, the slit is always cleanest when the exterior or annular layer has been scraped off. The dry and shrivelled membranous substance inclosed in the cavity of the quill forms part of an apparatus that has been subservient to the growth of the other parts of the feather, and consists of an imbricated series of conical capsules communicating with each other. The quill is also provided at each end with a small orifice (termed respectively the upper and the lower umbilicus) through which nourishment is conveyed to the other parts of the feather.

The shaft, which is a continuation of the quill, and composed of an attenuated pellicle of the same substance, gradually passes into a sub-quadrangular form, narrowing until it forms a point at the tip. The back is more or less convex for some distance from its origin, and the face is formed of two convex surfaces which are separated by a groove that runs along its whole length, or of two inclined planes meeting at an obtuse angle; while the lateral surfaces are more or less plane. The white medullary substance forming the interior of the shaft, is called the pith—a substance sui generis, and which supplies strength and nourishment to the feather.

The vane, or that part which gives the feather its breadth, consists of two webs (one on each side of the shaft), and is by much the most complicated of all its parts. The webs consist of a series of laminae called barbs or rays, which are set obliquely to, and are composed of the same material as, the shaft from which they spring. The barbs are arranged in close apposition, with their broad surfaces towards each other—a disposition that enables them to offer very considerable resistance to being bent out of their plane, or that direction in which they have to encounter the impulse and pressure of the air, particularly in the act of flight; while it admits of their yielding readily to the slightest pressure in the line of the shaft. The barbs taper to a point towards the outer edge of the vane; but at their base they are broad, (particularly in the great feathers of the wing,) and slightly hollowed on one side and convex on the other. This conformation both gives strength to each individual barb, and also enables it to afford support to its neighbour. But the most complex part of the mechanism of the vane is the apparatus of barbules, by means of which the barbs are kept firmly in apposition. The barbules are minute filaments that proceed from the upper part or edge of each barb, in two sets, one on either side, and having a direction, with respect to the barb, similar to that of the barbs with respect to the shaft. Those on the side next the quill are shorter, more adpressed, and curved upwards at the extremity; those on the side next the tip of the feather are longer, more patulous, and curved downwards; and when placed in apposition they form two distinct and continuous edges, the incurvate or anterior series of one barb overlapping and hooking into the recurvate posterior series of the barb next to it; and in this manner they give the barb a closeness and compactness of texture that resembles the effect of glutinous cohesion. When this connection is disturbed by external violence, the barbules reclasp when the barbs are again brought into apposition. When the barbs are pulled asunder in the plane of the web, their cohesion is found to be very considerable in most feathers: when the posterior barb is pulled downwards out of the plane of the web, the cohesion is found still greater: but when the anterior barb is pulled downwards, or the posterior barb upwards, there is no cohesion at all. The barbules themselves are frequently complicated by a similar apparatus, giving off laterally two series of filaments called barbicels; but these are much more sparse than those of the barbs, though they appear to serve a similar end, namely, that of retaining the barbules in apposition. When this clasping apparatus is wanting, as in the ostrich, the barbules hang loose and separate, and the feather is then termed a plume. In some birds, as the emu, two plumpy feathers arise from one quill; or even three, as exemplified in the cassowary.

There is in feathers the following gradation in respect to division:—1st, a feather may consist of a quill and a shaft, without any other part; 2d, of a quill, a shaft, and barbs destitute of barbules, as in the crest-feathers of the golden pheasant; 3d, of a quill, a shaft, barbs, and barbules, as in most birds; 4th, of a quill, shaft, barbs, barbules, and barbicels, as in the quills of the ring-tailed eagle, the albatross, and helmet-hornbill. In most birds, each feather possesses a downy tuft, more or less developed, at the upper end of Feathers, the quill; and this is termed the accessory plume. In the cassowary this development is two-fold. In the feathers of many birds the downy part occupies by far the greater portion, while in others it scarcely exists. As an example of feathers all downy may be mentioned the subcaudal feathers of the peacock, and the abdominal feathers of the eagle-owl, &c. Of such as have very little down may be mentioned the different species of penguin. On the different parts of the body in many birds there exist feathers of a piliform character, resembling stiff bristly hairs. Besides the feathers now described, the bodies of many birds are closely invested (underneath the feathers proper) with a soft down, the warmth or lightness of which is generally proportioned to the habits of the species; being usually most dense in aquatic birds, as in the eider-duck. Each down-feather consists of an extremely delicate shaft, from which proceed, in general, two sets of finely ciliated filaments. Down also constitutes the first covering of young birds, previous to the development of feathers, which they guide as it were through the skin, in the same manner that the old feathers during the moult of full-grown birds serve as the guibenaude of the new. It may be observed generally, that in some species the down presents certain modifications of structure different from that now described, as in the case of other kinds of feathers. In most birds, after the feathers have been removed, we find a number of simple feathers resembling hairs. These are the hairs singed off in a common fowl after it has been plucked. In the common pheasant their structure is as follows—from a very short bulbiform tube rises a very slender roundish piliform shaft, somewhat resembling a hair of the human head, but much smaller and straight, and giving off at its extremity two or three short simple barbs on either side.

Every feather may well be said to be "a mechanical wonder," when we consider the perfection of its parts and the mechanism employed in its formation—the vessels that secrete the fluid material, and the moulds and capsules by which the process of formation is conducted, until the period when the protecting sheath gradually withers and crumbles away, leaving the young feather to unfold its beautiful and complicated structure. Ornithologists give special names to the feathers of the different parts of the body, indicative of their position or particular function; but an enumeration of these would be of little interest to the general reader, and may be found in any elementary treatise on ornithology.

As intimately connected with the plumage, it should be noticed that the feathered race generally are provided with a kind of oiling apparatus, situated at the base of the tail, and consisting of a double gland with a pore, filled with an unctuous matter, which the bird expresses by means of its beak and distributes over its feathers, thereby rendering them impervious to moisture.

As to the colours of the plumage, the variety is almost infinite, presenting every gradation from the most sombre shade and purest white to hues that rival in brilliancy the richest gems or the most gorgeous flowers; as in the humming-bird, creeper, and sun-bird. The feathers of young birds rarely exhibit the colours they are destined to assume at a later period; the livery of the female too is generally less lively, and sometimes altogether different from that of the male bird: and sometimes the summer plumage is quite distinct from that of winter. Moulting usually takes place after the female has laid her eggs, (with less regularity in the domesticated birds), and is characterized by the dulness and roughened aspect of the plumage, and the temporary loss of voice among singing birds.

Uses to Man.—Feathers make a considerable article of commerce; particularly those of the ostrich, heron, swan, eider-duck, peacock, goose, common domestic fowl, &c., which are used for plumes and ornaments, beds, pens, &c.

It has often been said that geese are plucked in some parts of Great Britain several times a-year, and that in cold seasons many of them die from this barbarous custom; but we trust this account is exaggerated, and feel assured that such a practice is by no means general. The Somersetshire feathers are esteemed the best, and those from Ireland the worst. The best method of curing the smaller feathers, such as those used for bedding, is to expose them in a dry room to the sun, and, when they are dried, to put them in bags and beat them well with poles, in order to soften them and remove all adhering extraneous particles. The inhabitants of the high northern latitudes use the skins of several kinds of water-fowl, with the feathers on, as clothing. The Greenlanders make use of the downy skin of the eider-duck as a protection against cold. The feathers of the ostrich are much prized as ornamental articles of dress; and the capture of these birds for the sake of their plumes affords employment to many of the inhabitants of the desert. Feathers are also occasionally applied to a variety of other ornamental purposes, not the least curious of them being that of forming pictures, in the manner of mosaic, of the splendid feathers of the humming-bird, though it must be admitted that the effect is by no means commensurate with the labour required for their production. The French and Italians are particularly skilful in fabricating feathers into beautiful imitations of flowers.