vent erosion or wearing away, but they take soil 

 and sediment from the water which comes to 

 them and thus cause an upbuilding. Hence the 

 presence of beaver ponds along streams causes an 

 accumulation of sediment and soil. In time these 

 fill rocky channels and canons, widen and lengthen 

 valleys, and thus extend the productive area of 

 the earth. 



Beaver ponds are settling-basins, and in them 

 are deposited the heavier matter brought in by 

 the stream. In time the pond is filled, and if the 

 beaver do not raise the height of the dam, the 

 accumulated earthy matter becomes covered with 

 flowers or forests. 



On the headwaters of the Arkansas River in 

 Colorado some placer miners found gold in the 

 sediment of an inhabited beaver pond. In wash- 

 ing out the deposit of the pond they broke into 

 an enormous amount of loose material beneath, 

 that apparently had been piled in there by gla- 

 cial action. This material, when removed, was 

 found to have been resting in an ancient beaver 

 pond that was about thirty feet below the one at 

 the surface. 



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