46 ROMANCE OF THE BEAVER 
possible precaution not only to conceal myself, but 
to select a position down wind of the dam, where 
I remained sometimes during the greater part of 
the night. 
When a dam is abandoned, it is soon worn down 
by animals using it as a roadway, or it is overgrown 
by alders and willows, whose roots cause a certain 
amount of leakage, so that the pond is gradually 
drained, and in a very few years there is little to 
show that a dam ever existed in the place. 
Among the many interesting features of the 
dams, there is one which speaks most highly for 
the builder’s intelligence. That is the method 
adopted for taking care of the overflow. In most 
cases, the water finds its way through the loose 
brush near the crown. This is well enough under 
normal conditions, but when the dam is on a good- 
sized stream so that there is a large volume flowing 
from the pond, the beaver frequently make a spill- 
way or opening a few feet wide, and deep according 
to the conditions. These openings are quite clearly 
defined, and are evidently made with a full under- 
standing of their purpose. For when there is a 
scarcity of water, the intelligent animals close the 
opening as much as may be necessary. This 
shows how thoroughly they realise what they are 
doing when building their dams, and how they 
understand the value of controlling the outlet of 
the water. They are always ready to grapple with 
new problems, and no ordinary contingency appears 
