In theautumn of 1910 1 made notes concerning 

 eighteen houses. These I watched during Octo- 

 ber and November. Thirteen were plastered ; a 

 willow-grown one and a weed-grown one, both of 

 which had thick walls, were not plastered. The 

 remaining three were not greatly in need of ad- 

 ditional thickness, so received only a scanty cov- 

 ering of sticks. Two of these were broken into by 

 some animal during the winter, while none of the 

 others were disturbed. 



Beaver frequently show good judgment in that 

 important matter of selecting a site for the house. 

 Ice and sediment are two factors with which the 

 beaver must constantly contend. In the pond the 

 house is commonly placed in deep water, and 

 apparently where the depth around it will not be 

 rapidly reduced by the depositing of sediment. 

 Keeping the house-entrance, the harvest-pile 

 basin, and the canals from filling with sediment 

 is one of the difficult problems of beaver life. 



To guard against the rapid encroachments of 



the deposits of sediment, one group of beaver, 



apparently with forethought, built a dam that 



formed a pond from the waters of a small spring 



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