These dams are composed of stones, mud and tree branches, the base being ten or twelve feet in thickness sloping gradually upward to the summit.
In building their dams, the beaver does not thrust the ends of the stakes into the bed of the river, but lays them down horizontally, holding them in place by piling mud and stones upon them.

The logs which compose the dams are mostly from six to eight inches in diameter, though some have been found nearly two feet through.

The enormous number of such logs used may be imagined perhaps, when the ponderous character of the dams is remembered, and when it is stated that some of them are more than an eighth of a mile wide.

Every log, after being gnawed off the proper length, is stripped of its bark which is stored away for use as food during the winter.
The lodges of the beavers are composed principally of mud, moss and branches, circular in shape, the space within being seven feet in width and about half as high.

The walls are so thick that on the outside the corresponding dimensions are nearly three times as great as within.