38 ROMANCE OF THE BEAVER 
curving up and the other half down stream. On 
the whole, I think the subsidiary or supporting 
dams are more likely to be straight or have the 
curve away from the main structure. These 
» subsidiaries are of very great interest, as they offer 
a clear example of the beaver’s forethought, that is, 
if we are right in our conclusions, for we believe 
that they are placed below the most important dam 
in order to support it, by backing the water against 
its base, and also for the protection it gives when 
the pond is frozen, for then the mass of ice which 
forms in the usually quiet water acts as a powerful 
support to the principal structure, which has to 
resist a terrific pressure of ice, snow and water, 
especially at the time when winter is breaking up. 
But there are probably other reasons for the existence 
of these extra structures. It will be noticed that 
frequently there are a number of them—sometimes 
as many as eight or more at distances apart which 
may vary from a few feet up to several hundred. 
Some are of quite imposing size, while others may 
be only insignificant affairs a foot or two long and 
very roughly built. Between each dam, there is 
usually water of sufficient depth to allow the 
beaver to hide and so escape his enemies. Then 
again there is another important reason for these 
lesser dams. No matter how well the main 
structure is built, how carefully it is designed, an 
unusually heavy volume of water may cause it to 
break. The result of such a calamity would be 
