which a sufficient depth of water can be
maintained at all seasons of the year. Instinct rather than reason
prompts them to do this; still, on examining the dams, it is difficult
to suppose that they have been formed by animals. They are composed of
young trees, or of branches cut into lengths, each of about three feet,
and laid horizontally, one upon the other. While one party brings the
log, another follows with mud and stones, which they place upon it to
keep it from rising. At the bottom they are actually twelve feet thick,
though as they rise towards the top they diminish to the width of two
feet. When it is understood that some of these dams are between two and
three hundred yards long, it may be supposed what an enormous number of
small logs are required to make one.

What appears still more extraordinary is that when the stream runs
slowly, the dam is built directly across it, but should the current be
strong it is curved, with the convex side pointing up the stream, so
that it should the better withstand the force of the water. I
frequently found these dams with small trees growing out of them,
showing that they must have existed a number of years. In the lake thus
formed by the dam the beavers build their houses, or lodges, as they are
called by trappers. They are constructed in the same way as the dams,
with small logs kept together by clay and lined with moss, the roof
being plastered thickly with mud, which in time becomes so perfectly
hard, that it is difficult to break through it. It is a task which the
cunning wolverine--who is fond of beaver meat--can never accomplish, and
he prefers to pounce down on any of the animals which incautiously
venture forth, when he is in the neighbourhood.

These "lodges" outside measure as much as seven or eight feet in height,
and they are often from sixteen to twenty in circumference, but the
walls are so thick that the interior does not exceed three feet in
height and from six to eight in circumference. The entrance, which is
under water, is at such a depth that they cannot be frozen in.

It is a common idea among trappers, that the beaver uses his tail for a
trowel to flatten down the mud, but this is denied by more observing
naturalists, who assert that the tail is merely employed for swimming,
although when he is at work with his paws, he may flap it about, but not
for any other object.

One of the most extraordinary characteristics of the beaver is, th