Beavers build their houses of the same materials as their dams, and of various sizes, according to the number of the inmates.  These, however, do not often exceed four or eight old ones, and from six to fourteen young ones.  The houses are of a circular form, elevated some feet above the surface of the water; but the entrance is always low down beneath it.  They are more rudely constructed than the dams, too.  The wood is laid nearly horizontally, and crosswise; the branches, which project inwards, they cut off with their teeth.  First there is a layer of wood, and then one of mud and stones; and so they work on till a sufficient height is gained, when the roof, of rough branches, is placed on the top, and plastered down with mud and stones.