The roof is finished off with a thick layer of mud, laid on with wonderful smoothness and renewed every year.

The severe frosts of winter freeze the lodge into such a solid structure that the beaver is safe against the wolverine, which is unable to break through the wall, resembling the adobe structures found in Mexico and the Southwest.

Even the trapper who attempts to demolish one of the structures finds it tiresome labor, even with the help of iron implements.
The beavers excavate a ditch around their lodges too deep to be frozen.
Into this opens all their dwellings, the door being far below the surface, so that free ingress and egress are secured.
The half dozen beavers occupying a lodge arrange their beds against the wall, each separate from the other, while the centre of the chamber is unoccupied.

During summer they secure their stock of food by gnawing down hundreds of trees, the trunks or limbs of which are sunk and fastened in some peculiar manner to the bottom of the stream.

During the winter when the beaver feels hungry, he dives down, brings up one of the logs, drags it to a suitable spot and nibbles off the bark.
It is impossible fully to understand how this remarkable animal does its work, for as it never toils in the day time, it is out of the power of any one to watch its method.
The peculiar odoriferous substance, secreted in two glandular sacs near the root of the tail, is "castoreum," more generally known as "bark stone" among the trappers.