BEAVER, the English name for the genus Caator (Cuvier), one of the order of rodent or gnawing animals (llodentia, Cuvier, Clires, Lin n:cum), with 2 incisors, or cutting teeth, and 3 molars in each jaw, 20 in all; and particularly distinguished from all the rest of that order by a broad horizontally-flattened tail, which is nearly oval, and covered with scales. There aro five toes on each of the feet, but those of the hinder ones only are webbed, the webs extending beyond the roots of the nails. The second toe of these last is furnished with a double nail, or rather with two, one like those of the other toes, and another beneath it, situated obliquely with a sharp edge directed downward& There is also, as Sir John Richardson observes, n less perfect double nail on the inner toe of the hind feet.
The incisor teeth of the Beaver are broad, flattened, and protected anteriorly by a coat of very hard orange-coloured enamel, the rest of the tooth being of a comparatively soft substance, whereby a cutting chisel-like edge is obtained; and indeed, no edge tool, with all its combinations of hard and soft metal, could answer the purporie better. In fact, the beaver's incisor tooth is fashioned much upon the 88111e principle as that followed by the tool-maker, who forms a cutting instrument by a skilful adaptation of hard and soft materials till lie produces a good edge.
But the natural instrument has one great advantage over the artificial tool; for the former is so organised that as fast as it is worn away by use a reproduction and protrusion from the base takes place, and thus the two pairs of chisel-teeth working opposite to each other are always kept in good repair, with their edges at the proper cutting angle. %%lien injury or disease destroys one of these incisors, its antagonist, meeting with no cheek to resist the protrusion from behind, is pushed forward into a monstrous elongation. So hard is the enamel, and so good a cutting instrument is the incisor tooth of the Beaver, that when fixed in a wooden handle, it was, according to Sir John Richardson, used by the Northern Indians to cut bone, and fashion their horn-tipped spears, fie., till it was superseded by the introduction of iron, when the beaver-tooth was supplanted by the English file.
The power of these natural tools is well described by Lewis and Clarke, who saw their effects on the banks of the Missouri. " The ravages of the beaver," say they, "aro very apparent ; in one place the timber was entirely penetrated fur a mace of throe acres in front on the river, and ono in depth, and great part of it removed, although the trees were in large quantities, and some of them as thick as the body of a man." Sir Joh', Richardson thus speaks of this part of their operations :— "When the beaver cuts down a tree it gnaws it all round, cutting it however somewhat higher on the one side than the other, by which the direction of its fall is determined. The stump is conical, and of
such a height as a beaver sitting on his hind quarters could make. The largest tree I observed cut down' by them, was about the thickness of a man's thigh (that is G or 7 inches in diameter), but 3Ir. Graham says that ho has seen them cut down a tree which was 10 inches in diameter." Beavers have no canine teeth.
Castor Fiber of Linnaeus (Castor A ntericanua of F. Cuvier), the American Beaver, is the animal of whose sagacity, and even social polity, such wonderful tales have been told. The best account of this animal is that given by Hearne :— " The beaver," he says, "being 80 plentiful, the attention of my companions was chiefly engaged on them, as they not only furnished delicious food, but their skins proved n valuable acquisition, being a principal article of trade, as well as a serviceable one for clothing. The situation of the beaver-houses is various. Where the beavers are numerous they are found to inhabit lakes, ponds, and rivers, as well as those narrow creeks which connect the numerous lakes with which this country abounds; but the two latter are generally chosen by them when tho depth of water and other circumstances are suitable, as they have then the advantage of a current to convey wood and other necessaries to their habitations, and because, in general, they are mom difficult to be taken than those that are built in standing water. They always choose those parts that have such a depth of water as will resist the frost in winter, and prevent it from freezing to the bottom. The beavers that build their houses in small rivers or creeks, in which water is liable to be drained off when the back supplies are dried up by the frost, are wonderfully taught by instinct to provide against that evil by making a dam quite across the river, at a convenient distance from their houses. The beaver-dams differ in slmpe according to the nature of the place in which they are built. If the water in the river or creek have but little motion the dam is almost straight; but when the current is more rapid it is always made with n considerable curve, convex towards the stream. The materials made use of are drift-wood, green willows, birch, and poplars, if they can be got ; also mud and stones intermixed in such a manlier as must evidently contribute to the strength of the dam ; but there is no other order or method observed in the damns, except that of the work being carried on with a regular sweep, and all the parts being made of equal strength. In places which have been long frequented by beavers undisturbed, their dams, by frequent repairing, become a solid bank, capable of resisting n great force both of water and ice; and as the willow, poplar, and birch generally take root and shoot up, they by degrees form n kind of regular planted hedge, which 1 have seen in some places so tall that birds have built their nests among the branches.