the beavers tunnel their two runways into
the centre of the mass from an underwater level on the outside to an
over-water level on the inside of the mound. Next, by gnawing away the
inside sticks and excavating the inner mass, the inside chamber is
formed, measuring anywhere from four to fourteen feet in width, and a
little over two feet in height, with its walls finished fairly smooth.
Furthermore, the chamber is provided with two floors each of which
covers about half the room. While the lower floor rises from three to
six inches above the water level, the upper floor rises from four to
eight inches above the lower floor. The tunnels open in the lower
floor and it is the lower floor or level that is used as a drying place
and a dining room. The upper level, covered with a mattress of
shredded wood, grass, or moss, forms the living and sleeping half of
the chamber. Though in winter time most of their meals are eaten in
the house, the green, bark-covered sticks being brought into the
chamber through the straightest tunnel, the house is kept quite clean
and free of all rubbish or filth. In fact, beavers are better
housekeepers than some human beings I have known.

A certain amount of ventilation is derived from a few little chinks in
the apex of the roof. During the first freezing nights of late fall
the beavers plaster the above-water dome of their house with mud which
they carry up between their forelegs and chin from the lake bottom, and
placing it upon the roof of their house, spread it about in a thick
coating, not with their tails, but with their forefeet, where it soon
freezes into so solid a mass that it protects the inmates from the
attacks of both the severest winter weather and the most savage of
four-footed enemies. So strong indeed does the roof then become that
even a moose could stand upon it without it giving way. While some
writers doubt that beavers plaster the outside of their house with mud,
I wish to add that I have not only examined their houses before and
after the plastering was done, but on several moonlight nights I have
actually sat within forty feet of them and watched them do it.

The winter supply of food, being mostly poplar bark, is derived from
the branches of green trees which the beavers cut down in the autumn
for that very purpose. While engaged in gnawing down trees the beavers
usually work in pairs--one cutting while the other rests and also acts
as a sentinel to give war