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logs or large trees across the stream. I have, how- 

 ever, seen a few real log dams, but in these the 

 logs were placed parallel to the flow of water. 

 One of these was in the Sawtooth Mountains of 

 Idaho. Here a snow-slide swept several hundred 

 trees down the mountain. This wreckage was 

 piled on the bank of a stream. Beaver in a colony 

 a short distance away accepted this gift of the 

 gods, and of these unwieldy logs built a dam 

 about two hundred feet downstream from where 

 the avalanche had piled the logs. This dam was 

 a massive affair, about forty feet long and eight 

 feet high. It really appeared more like a log jam 

 than a dam, but it served the purpose intended 

 and raised the level of the river so that the water 

 overflowed to one side and spread in a broad 

 sheet against a cliff and through a grove of as- 

 pens, which the beaver proceeded to harvest. 



The majority of dams are made of slender 

 green poles which are placed lengthwise with the 

 flow for the bottom, and set braced with the end 

 upstream a foot or so higher than the down- 

 stream end. With these there are occasionally 

 used small limby trees. The large end of the tree 

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