saw was one across the narrow neck of a rudely 

 bell-shaped basin that was about two hundred 

 feet in length. The material for this dam came 

 from a grove of aspens that extended into one 

 side of the basin. The floor of this basin was 

 partly covered with a few inches of water. In start- 

 ing the dam the beaver evidently knew where 

 they wanted to build it. This was not by the 

 aspen grove where the materials were convenient, 

 where the dam would need to be about one hun- 

 dred and twenty feet long, but was about fifty 

 feet farther on, where a dam of only forty feet 

 was required. This dam when completed bowed 

 seven feet against the enclosed water. The 

 beaver commenced building at the end nearest 

 the grove of aspens, pulling and dragging the 

 poles the fifty feet to it. They laid these aspen 

 poles, which were two to five inches in diameter 

 and from four to twelve feet in length, at right 

 angles to the length of the dam, and usually 

 placed the large end upstream or against the cur- 

 rent. But the water was shallow, and the trans- 

 portation of these poles to the dam was difficult. 

 Accordingly a ditch or canal was dug from the 



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