WILD ANIMALS. 97

They construct their houses at a convenient dis- tance from the dam, of the same materials; and the principal objects appear to be, having a dry bed to lie on, and security. The walls, and particularly the roof, are often more than five feet thick; and they never give them the last coat of mud-plaster until the frost sets in, which freezes it so hard, that the Wolvereen, the greatest enemy of the species, cannot easily break through. Some of the large houses have several apartments; but‘it appears that each is occu- pied by a whole family. There is no passage into them from the land side ; and they have vaults on the banks of the rivers to retreat to, when they apprehend danger. They drag pieces of wood with their teeth ; the mud and small stones they carry between their fore-paws and their throat. They execute their work wholly in the night. ‘Vhen the increase of their numbers makes it necessary to erect additional apartments, or when they shift to another situation, they begin to cut down the wood requisite early in summer, and commence building in August; but do not complete their work until cold weather sets in. They feed on the bark of trees, preferring that of the poplar and willow, and float down wood, that they cut in summer, to their habitations, for winter provi- sion; but their principal article of food is a thick root that grows in the bottom of rivers and lakes. In summer, they feed on various herbs, berries, &c.

As soon as the ice breaks up in the spring, they leave their houses, and ramble about during summer;

and, if they do not fix on a more desirable situation, VOL. I. a