tool, wielded by
a muscular human arm" (Martin). They operate seated on their hind
quarters, and they make their incision in the wood with a feather
edge. It was once supposed that they always take care so to direct
their wood-cutting task that the tree may fall on the water-side, but
this is by no means the case, and appears to be simply due, as Martin
points out, to the fact that trees by the water-side usually slope
towards the water. The austerity of labour alternates, it may be
added, with the pleasures of the table. From time to time the Beavers
remove the bark of the fallen trees, of which they are very fond, and
feed on it.

Mr. Lewis H. Morgan studied the American Beaver with great care and
thoroughness, more especially on the south-west shore of Lake
Superior; he devotes fifty pages to the dams, and it is worth while to
quote his preliminary remarks regarding them. "The dam is the
principal structure of the beaver. It is also the most important of
his erections as it is the most extensive, and because its production
and preservation could only be accomplished by patient and
long-continued labour. In point of time, also, it precedes the lodge,
since the floor of the latter and the entrances to its chamber are
constructed with reference to the level of the water in the pond. The
object of the dam is the formation of an artificial pond, the
principal use of which is the refuge it affords to them when assailed,
and the water-connection it gives to their lodges and to their burrows
in the banks. Hence, as the level of the pond must, in all cases, rise
from one to two feet above these entrances for the protection of the
animal from pursuit and capture, the surface-level of the pond must,
to a greater or less extent, be subject to their immediate control. As
the dam is not an absolute necessity to the beaver for the maintenance
of his life, his normal habitation being rather natural ponds and
rivers, and burrows in their banks, it is, in itself considered, a
remarkable fact that he should have voluntarily transferred himself,
by means of dams and ponds of his own construction, from a natural to
an artificial mode of life.

"Some of these dams are so extensive as to forbid the supposition that
they were the exclusive work of a single pair, or of a single family
of beavers; but it does not follow, as has very generally been
supposed, that several families, or a colony, unite for the joint
construction of a dam. Aft