, is a swamp not likely to freeze to the bottom, and if
with a stream running through it, all the better. By the side of this
stream, or often on a little islet in the midst, they construct a
dome-shaped pile, hollow within, and very much like the house of the
beaver. The materials used are grass and mud, the latter being obtained
at the bottom of the swamp or stream. The entrance to this house is
subterranean, and consists of one or more galleries debouching under the
water. In situations where there is danger of inundation, the floor of
the interior is raised higher, and frequently terraces are made to admit
of a dry seat, in case the ground-floor should get flooded. Of course
there is free egress and ingress at all times, to permit the animal to
go after its food, which consists of plants that grow in the water close
at hand.

The house being completed, and the cold weather having set in, the whole
family, parents and all, enter it, and remain there during the winter,
going out only at intervals for necessary purposes. In spring they
desert this habitation and never return to it.

Of course they are warm enough during winter while thus housed, even in
the very coldest weather. The heat of their own bodies would make them
so, lying as they do, huddled together, and sometimes on top of one
another, but the mud walls of their habitations are a foot or more in
thickness, and neither frost nor rain can penetrate within.

Now, a curious fact has been observed in connection with the houses of
these creatures. It shows how nature has adapted them to the
circumstances in which they may be placed. By philosophers it is termed
"instinct"; but in our opinion it is the same sort of instinct which
enables Mr Hobbs to pick a "Chubb" lock. It is this:--

In southern climates--in Louisiana, for instance--the swamps and rivers
do not freeze over in winter. There the muskrat does not construct such
houses as that described, but is contented all the year with his burrow
in the banks. He can go forth freely and seek his food at all seasons.

In the north it is different. There for months the rivers are frozen
over with thick ice. The muskrat could only come out under the ice, or
above it. If the latter, the entrance of his burrow would betray him,
and men with their traps, and dogs, or other enemies, would easily get
at him. Even if he had also a water entrance, by which he might escape
upon the invasion of his burrow