Beaver, or Castor, a qua-druped, of which there are three species.

1. The fiber, or common beaver, which inhabits the northern parts of Europe, Asia, and America, in the banks of rivers or lakes, at a distance from the dwellings of men, and is there a gregarious animal. In populous countries, however, such as Germany, Prussia, and Poland, it is a solitary creature; and the skin, on account of its constant residence under ground, 1, 5 less valuable than that of the social beaver. The latter is principally found in North America, where many hundreds settle to gether on the bank of a river, and construct regular habitations, with admirable ingenuity, such as far excel the primitive huts and hovels erected by mankind. They chiefly subsist on lobsters and other fish, and attain to an age of fifteen or twenty years. The beaver's tail is from six to nine inches long, and one inch thick; its flesh has the flavour of fish, and is esteemed as delicate food. Near the rectum of both sexes, there are two little bags, about the size of a hen's egg, containing a brownish oily matter, called castor, which is a peculiar deposition of fat interwoven with cellular membrane. This sub-stance has a disagreeable, narcotic smell, and a bitterish, acrid, nauseous taste. By drying it in the smoke of a chimney, it may be preserved for seven or eight years. It has long been celebrated as a nervine and anti-hysteric medicine, though its efficacy has often been doubted. Yet, we are convinced from experience, that the genuine castor affords an excellent remedy, and may be employed with advantage in languid habits, and such constitutions, in general, as evince neither a rigid fibre nor a disposition to plethora. Even Hippocrates prescribed it in hysteric cases ; and Galen informs us, that Archtgenes had written a treatise on the subject. This gelatinous and oily concrete is taken in doses from five to twenty grains, with sugar; or its virtues may be extracted by water, as well as spirit of wine, which latter forms a stronger preparation, but more heating than solid castor itself.

In commerce, a distinction is made between fresh, dry, and fat beaver-skins: the first of these are obtained from animals caught in winter ; the second sort from those killed during summer, the hair of which only is used in the manufacture, of hats; and the third, or fat sort, are such as have been carried for some time on the naked bodies of the American Indians, who, as it were, tan the skin with perspirable matter. These furs are -most valuable, while the hair of the others is manufactured into gloves, stockings, etc. but that which is short and silky, is used for hats. Each beaver, when full grown, is as large as a middle sized dog, and yields about twenty-four ounces of fine hair. The skin serves for covering saddles, trunks, and other articles.

All those advantages, however, are not equivalent to the damage done by the beaver to forests . and sluices : and as they yearly become more scarce in America, while the price of their skin and hair advances, it is doubtful whether they ought to be spared, or exterminated.

2. The moschatus, or water- rat, of Clusius, is found in Lapland and Russia, on the banks of the Volga and Yaik: it is devoured by pikes and other fish, to which it imparts so strong a flavour of musk, as to render them unfit for the table. Its scent much resembles that of the former species, especially about the tail, from which the cunning Russians express a juice very similar to the genuine musk. Hence, most of the castor sold in the London shops, consists of this inferior sort, or at least is much adulterated with it, so that the druggists themselves are frequently deceived.

3. The zibethicus, or musk-rat of North America, the fur of which is much esteemed for its softness and beauty. It is remarkable that, during summer, this animal has a most exquisite smell of musk, which it entirely loses in winter. Probably this agreeable perfume is derived from the Calamus aroma-ticus, or sweet water flag, which is the favourite food of the musk-rat.—See Artificial Musk.