THE BEAVER. 15 
that it intercepts all large floating objects, and every 
log or branch that may happen to be thrown into the 
river is arrested by the dam, and aids in increasing its 
dimensions. 
Mud and earth are also continually added by the 
Beavers, so that in process of time the dam becomes as 
firm as the land through which the river passes, and is 
covered with fertile alluvium. Seeds soon make their 
way to the congenial soil, and in a dam of long standing, 
forest trees have been known to grow, their roots adding 
to the general stability by binding together the materials. 
It is well known that the fertile islands formed on coral 
reefs are stocked in a similar manner. Originally, the 
dam is seldom more than a yard in width where it over- 
tops the water, but these unintentional additions cause a 
continual increase. 
The bark with which the logs were originally covered 
is not all eaten by the animals, but stripped away, and 
the greater part hidden under water, to serve for food in 
the winter time. <A further winter provision is also made 
by taking the smaller branches, diving with them to the 
foundations of the dam, and carefully fastening them 
among the logs. When the Beavers are hungry, they dive 
to their hidden stores, pull out a few branches, carry them 
on land, nibble away the bark, and drop the stripped logs 
on the water, where they are soon absorbed by the dam. 
We have now seen how the Beavers keep the water to 
the required level, and we must next see how they make 
use of it. The Beaver is essentially an aquatic mammal, 
never walking when it can swim, and seldom appearing 
quite at its ease upon dry land. It therefore makes its 
houses close to the water, and communicating with it by 
means of subterranean passages, one entrance of which 
passes into the house or “ lodge,” as it is technically named, 
