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therefore, whatever that cause was, has been concerned in the origin; has governed the production of these different animal forms.
When we pass on to smaller animals, or to the inhabitants of a different element, the resemblance becomes more distant and more obscure, but still the plan accompanies us.
And what we can never enough commend, and which it is our business at present to exemplify, the plan is attended through all its varieties and deflections, by subserviences to special occasions and utilities.
I. The covering of different animals (though, whether I am correct in classing this under their anatomy, I don't know) is the first thing which presents itself to our observation; and is, in truth, both for its variety, and its suitableness to their several natures, as much to be admired as any part of their structure. We have bristles, hair, wool, furs, feathers, quills, prickles, scales; yet in this diversity both of material and form, we cannot change one animal's coat for another, without evidently changing it for the worse: taking care how ever to remark, that these coverings are, in 9, 3 many many cases, armour as well as clothing; intended for protection as well as warmth.
The human animal is the only one which is naked, and the only one which can clothe itself. This is one of the properties which renders him an animal of all climates, and of all seasons. He can adapt the warmth or lightness of his covering to the temperature of his habitation. Had he been born with a fleece upon his back, although he might have been comforted by its warmth in high latitudes, it would have oppressed him by its weight and heat, as the species spread towards the equator.
What art, however, does for men, nature has, in many instances, done for those animals which are incapable of art. Their clothing, of its own accord, changes with their necessities. This is particularly the case with that large tribe of quadrupeds which are covered with furs. Every dealer in hareskins, and rabbit-skins, knows how much the fur is thickened by the approach of winter. It seems to be a part of the fame constitution and the fame design, that wool, in hot countries, degenerates, as it is called, but in truth (most happily for the animal's case) passes into hair;
whilst whilst, on the contrary, that hair, in the dogs of the polar regions, is turned into wool, or something very like it. To which may be reserred, what naturalists have remarked, that bears, wolves, foxes, hares, which do not take the water, have the fur much thicker on the back than the belly: whereas in the beaver it is the thickest upon the belly; as are the seathers in water fowl. We know the final cause of all this; and we know no other.
The covering of birds 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 lise which the animal is to lead, as that, I think, we should have had no conception of any thing equally perfect, if we had never seen it, or can now imagine any thing more so. Let us suppose (what is possible only in supposition) a person who had never seen a bird, to be presented with a plucked pheafant, and bid to set his wits to work, how to contrive for it a covering, which shall unite
the qualities of warmth, levity, and least resistance to the air, and the highest degree of each; giving it also as much of beauty and ornament as he could afford. He is the person to behold the work of the Deity, in this part of his creation, with the sentiments which are due to it.
The commendation, which the general aspect of the feathered world seldom fails of exciting, will be increased by further examination. It is one of those cases in which the philosopher has more to admire, than the common observer. Every feather is a mechanical wonder. If we look at the quill, we find properties not easily brought together, strength and lightness. I know few things more remarkable, than the strength and lightness of the very pen, with which I am writing, If we cast our eye to the upper part of the stem, we see a material, made for the purpose, used in no other class of animals, and in no other part of birds; tough, light, pliant, elastic. The pith, also, which feeds the seather, is, amongst animal substances, fui generis; neither bone, flesh, membrane, nor tendon.
But the artificial part of a feather is the beard, or, as it is sometimes I believe called, the vane. By the beards are meant, what
are fastened on each fide the stem, and what constitute the breadth of the feather ; what we usually strip off, from one side or both, when we make a pen. The separate pieces, or laminæ, of which the beard is composed, are called threads, sometimes filaments, or rays, Now the first thing which an attentive observer will remark is, how much stronger the beard of the feather, shows itself to be, when pressed in a direction perpendicular to its plane, than when rubbed, either up or down, in the line of the stem; and he will soon discover the structure which occasions this difference, viz. that the laminæ whereof these beards are composed, are flat, and placed with their flat sides towards each other; by which means, whilst they easily bend for the approaching of each other, as any one may perceive by drawing his finger ever so lightly upwards, they are much harder to bend out of their plane, which is the direction in which they have to encounter the impulse and pressure of the air; and in which their strength is wanted, and put to the trial.
This is one particularity in the structure of a feather : a second is still more extraordinary. Whoever examines a feather, cannot help