THE DAM 51 
fairly good evidence that the dam built by the beavers must 
have existed about one thousand years ago. 
USES OF DAMS 
Beavers build dams for various reasons. The primary 
purpose for which one is made is to provide a sufficient 
depth of water in which the animals can move about in safety 
and to which they can retreat from their enemies, and in 
which they can transport their food supplies; deep enough 
to protect the entrances to the lodge, when there is a lodge, 
and the burrows in the banks. The pond must also be of 
such depth that when frozen in winter there will still be 
water enough to enable the inhabitants to move about under 
the ice and to provide a place for the winter storage of food. 
Such is a brief statement of the requirements of a pond 
intended for residential purposes. 
But there are other uses to which a pond is put, and not 
every pond in a colony is inhabited by the beavers. They 
are often built to provide water in which food supplies may 
be floated to the main pond. Thus the “Deadwood Dam 
Pond” in the Moraine Colony near Longs Peak, described 
by Mills, was made to enable the builders to cut aspens in a 
grove on the shore of the pond and float them across, and 
thence carry them to the pond where they lived. This 
Deadwood Dam Pond was not on the stream but was filled 
by means of a canal dug for that purpose. 
On a stream we often find dams above and below the main 
pond. These have several uses. All of them may be 
used for carrying food to the principal pond; those upstream 
from the latter are serviceable in controlling flood waters 
and preventing them from rushing in too great a volume into 
the latter and perhaps endangering it. Incidentally atten- 
tion should be called to the fact that the whole series of 
beaver dams on a stream may be of great service to man in 
