tom, and here they set to work. It was a very desirable situation in
every respect. At one side stood a large tree, so close that it could
probably be used as a buttress for the dam when the latter was
sufficiently lengthened to reach it; while above the shallow the ground
was low and flat on both sides for some distance back from the banks, so
that the pond would have plenty of room to spread out. If they could
have spoken they would probably have said that the place was a dam site
better than any other they had seen.

[Illustration: _Building the Dam._]

Alder bushes laid lengthwise of the current were the first materials
used, and for a time the water filtered through them with hardly a
pause. Then the beavers began laying mud and stones and moss on this
brush foundation, scooping them up with their hands, and holding them
under their chins as they waddled or swam to the dam. The Beaver himself
was not very good at this sort of work, for his right hand was gone, as
we know, and it was not easy for him to carry things; but he did the
best he could, and together they accomplished a great deal. The mud and
the grass and such-like materials were deposited mainly on the upper
face of the dam, where the pressure of the water only sufficed to drive
them tighter in among the brush; and thus, little by little, a smooth
bank of earth was presented to the current, backed up on the lower side
by a tangle of sticks and poles. Its top was very level and straight,
and along its whole length the water trickled over in a succession of
tiny rills. This was important, for if all the overflow had been in one
place the stream might have been so strong and rapid as to eat into
the dam, and perhaps carry away the whole structure.

The first year the beavers did not try to raise the stream more than a
foot above its original level. There was much other work to be done--a
house to be built, and food to be laid in for the winter--and if they
spent too much time on the dam they might freeze or starve before
spring. A few rods up-stream was a grassy point which the rising waters
had transformed into an island, and here they built their lodge, a
hollow mound of sticks and mud, with a small, cave-like chamber in the
centre, from which two tunnels led out under the pond--"angles," the
trappers call them. The walls were masses of earth and wood and stones,
so thick and solid that even a man with an axe would have found it
difficult to penetrate t