THE BEAVER. 181 



injure that organ to a degree altogether incommensurate 

 with the downward impulse it would impart to the pile, 

 and great as its sagacity may be, it has not been able to 

 invent a pile driver worked either by mechanism or by 

 steam. Its dams are formed from the trunks and arms 

 of trees floated down to a shallow point in the stream; 

 here they lodge, others are piled upon them, the boughs 

 interlaced, and stones and clay from the bottom are heaped 

 upon them, until the whole forms a solid mass, capable 

 of resisting the stream even in flood. Where the flow of 

 water is but small, the dam is constructed in a straight line 

 across it ; where it is liable to be swollen greatly by rain, 

 it is built in a concave form, so as to break the force of the 

 current. Man himself could not better appreciate the 

 necessities of the situation. In streams where the supply of 

 water is constant it is unnecessary for the beaver to build 

 dams, as the purpose of these is only to maintain the 

 water at a level sufficient to cover the entrance of their 

 houses. Even in these cases the beaver often miscalculates 

 the length of the wolverine's fore leg, and the latter will lie 

 for hours patiently awaiting the passage in or out of a 

 beaver, and then grasp it under water. That the beaver 

 should allow the wolverine this opportunity detracts some- 

 what from its character for foresight. 



The houses themselves are built much after the fashion 

 of the dams, except that timber forms a smaller proportion of 

 the mass, which is composed principally of mud and stones. 

 Sometimes, especially when circumstances restrict the space 

 available for house building, two or more families will 

 live under the same roof, but each abode has its separate 

 entrance, and privacy is thus preserved. 



