hundred feet in length, is to protect the home of the builders by 

 keeping the water deep enough to cover the entrance. This home 

 is usually a burrow in the bank and, as the dyke causes the water 

 to rise around and about it, the height is increased and the struc- 

 ture strengthened by poles and mud, until the typical "Beaver 

 Lodge'' results rather from the flooding due to the dam than from 

 any deliberate plan. To find material these industrious creatures 

 must often fell trees, frequently a foot in diameter, which they do 

 by gnawing parallel grooves around the trunk and chiseling out the 

 wood between with their strong sharp teeth, then gnawing other 

 circles deeper in and repeating the process until the tree falls, usual- 

 ly into the water. At once they begin to trim off the branches, the 

 bark of which furnishes them with their chief food, many of them 

 being fastened under water for their winter's supply. Next, the 

 wood is cut into lengths of from three to five feet and dragged to 

 the edge of the stream, from which it may easily be floated to the 



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