88 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 sufficiei^t 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 



