or BEAVER, in zoology, a genus of quadrupeds belonging to the order of glires. The fore-teeth of the upper jaw are truncated, and hollowed in a transverse angular direction. The tops of the fore-teeth of the lower-jaw lie in a transverse direction; and the tail is depressed. There are three species of castor, viz. 1. The fiber, with a plane ovated tail, is found on the banks of rivers in Europe, Asia, and America. It is from the inguinal glands of this animal that the castor is obtained; it is contained in pods or pouches which resemble a dog's testicles.

Several writers have taken notice of the ingenuity of American beavers in making their houses, of which we shall here give some account. The first thing they do when they are about to build, is to assemble in companies, sometimes of two or three hundred together; then they choose a place where plenty of provisions are to be had, and where all necessaries are to be found proper for their use. Their houses are always in the water, and when they can find neither lake nor pond, they endeavour to supply that defect by stopping the current of a brook or small river, by means of a dam. To this end they first cut down trees in the following manner: Three or four beavers will go to work about a large tree, and by continually gnawing at it with their teeth, they at last throw it down, and so contrive matters that it always falls, towards the water, that they may have the least way to carry it, when they have divided it into pieces. After they have done this, they take each piece by itself, and roll it towards the water, where they intend to place it.

These pieces are more or less thick and long, according to the nature and situation of the places where they are required. Sometimes they make use of the large trunks of trees, which they lay down flat; sometimes the dam only consists of branches as thick as one's thigh, which are supported by stakes interwoven with the branches of trees; and all the vacant places are filled up with a sort of clay, in such a manner, that no water can pass through them. They prepare the clay with their paws or hands; and their tails serve instead of a carriage, as well as a trowel to lay on their clay.

The foundation of the dams are generally ten or twelve feet thick, and they lessen gradually till they come to two or three. They always observe an exact proportion, insomuch, that the most curious architects are not capable of performing their work more regularly. That side towards the current of the water is always sloping, but the other is perpendicular.

The construction of the houses is altogether as wonderful; for they are generally built upon piles in small lakes, which are formed by making of the dams. Sometimes they are on the bank of a river, or on the extremity of a point of land, which advances into the water. They are of a round or oval form, and the top of them is like a dome.

This description of one of their houses which was examined and measured, will perhaps give the reader more satisfaction than an account in general. It was about three parts surrounded with water, and the other part was joined to the land. It was round, with an oval dome at the top, and the height above the surface of the water was eight feet. It was about forty feet in diameter, and one hundred and twenty in circumference, which perhaps may seem strange, because the proportion is geometrical; this however is fact, for it was measured several times. The part that joined to the bank was not made out of it, but was of the same materials with the rest.

The bottom of the house was of earth, or soil, with pieces of wood laid in it, above three inches in circumference; then a parcel of poplar sticks laid with one end in the house, and another slanting a long way under water; then a layer of earth again, and then poplar sticks, which were repeated to the height of eighteen inches. From thence to the top of the house there was a mixture of earth, stones, and sticks, curiously put together; and the whole was covered with sods, that had long grass growing thereon. The largest pieces of wood made use of near the top, were about three inches in diameter, and all the rest was small stuff, not above two or three fingers thick.

The outermost part of this house did not stand farther out in the creek than the edge of the shore; but that which brought the water almost round the house were the trenches, which were made by taking out the earth; these were nine feet in the broadest part, and eighteen feet in length. The creek at the front of the house was six and thirty feet broad, and seemed to be pretty deep. The house was so contrived as to be very solid, for there was no breaking into it without an ax; and in the frosty season it was quite impenetrable. From this house there were several paths into the wood, through which they drew the sticks and trees, which they made use of for food or building.

The wall of the house was two feet thick; and it was covered with smooth clay on the inside in such a manner that it would not admit the least breath of air. Two thirds of the structure was out of the water; and in the upper part, each beaver had his particular ticular place, whereon leaves were strewed to lie upon.

There never was any filth seen in any of these housetops, which are made like an oven in the inside, with a passage for these animals to go and bathe in the water. One of these will generally lodge about eight or ten beavers, though sometimes they have held thirty; but this is very uncommon.

These creatures are never surprised by the frost and snow; for they finish their work towards the end of September; and then they lay in provisions for the winter. In the summer-time they live upon fruits, and the barks and leaves of trees; and they likewise catch small fish, and particularly crabs or craw-fish. However, their winter-provision is the tender branches of trees, particularly poplar, of which they seem to be very fond. It is usually said, and upon pretty good authority, that these beavers make the walls of their houses of a thickness in proportion to the severity of the succeeding winter; which if true, these animals must be furnished with uncommon foresight.

When there are great floods caused by the melting of the snow, which damage the houses of the beavers, they then leave them, and shift for themselves as well as they can; however, the females return as soon as the waters are abated; but the males keep the field till July, when they assemble again to repair the damage that has been done by the flood, either to their houses or dams. When any of their houses are demolished by the hunters, they never repair them again, but build others quite new. Some authors have said, that the beavers make several rooms in their houses; but this upon examination has been found to be false.

In hunting the beavers, the savages sometimes shoot them, always getting on the contrary side of the wind; for they are very shy, quick in hearing, and of a very keen scent. This is generally done when the beavers are at work, or on shore feeding on poplar bark. If they hear any noise when at work, they immediately jump into the water, and continue there some time; and when they rise, it is at a distance from the place where they went in.

They sometimes are taken with traps: these are nothing but poplar sticks laid in a path near the water; which when the beaver begins to feed upon, they cause a large log of wood to fall upon their necks, which is put in motion by their moving of the sticks, and consequently requires an ingenious contrivance. The savages generally prefer this way of taking them, because it does not damage their skins.

In the winter time they break the ice in two places at a distance from the house, the one behind the other. Then they take away the broken ice with a kind of a racket, the better to see where to place their stakes. They fasten their nets to these, which have large meshes, and sometimes are eighteen or twenty yards in length. When these are fixed, they proceed to demolish the house, and turn a dog therein; which terrifying the beaver, he immediately leaves it, and takes to the water; after which, he is soon entangled by the net.

Mr. Lawson who was general surveyor of North Carolina, affirms, that beavers are very plenty in that country. He confirms what has been said about their ingenuity in building of their dams and houses, and observes, that their food is chiefly the bark of trees and shrubs; such as that of the sassafras, ash, sweet gum, and several others. He adds, that if they are taken young, they will become very tame; but then they will do a great deal of mischief in the orchards, by breaking the trees. They will likewise block up the doors of the houses in the night, with the sticks and wood which they bring thither. He farther informs us, that it is certain death for them to eat anything that is salt. The flesh is looked upon as very delicate food.

2. The mofchatus, with a long, compressed, lanceolate tail, and palmated feet. It is the exotic water-rat of Clusius, and is a native of Russia.

3. The zibethicus, or musk-rat, with a long, compressed, and lanceolated tail, and the toes of the feet separate from each other. The follicles of the tail are said to banish moths and other insects from cloaths, &c. For this reason the inhabitants of Russia and Canada sew them into the folds of their cloaths, to keep off vermin and contagious diseases.

Castor is also the name of a market-town of Lincolnshire, twenty miles north-east of Lincoln: W. long. 12°, and N. lat. 53° 30'.