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On the upper course of Grand River in Col- 

 orado, I once made an extensive examination of 

 some old beaver-works. Series of beaver-dams 

 had been extended along this stream for several 

 miles, as many as twenty dams to the mile. Each 

 succeeding dam had backed water to the one 

 above it. These had accumulated soil and formed 

 a series of terraces, which, with the moderate 

 slope of the valley, had in time formed an exten- 

 sive and comparatively level meadow for a great 

 distance along the river. The beaver settlement 

 on this river was long ago almost entirely de- 

 stroyed, and the year before my arrival a cloud- 

 burst had fallen upon the mountain-slope above, 

 and the down-rushing flood had, in places, eroded 

 deeply into the deposits formed by the beaver- 

 works. At one place the water had cut down 

 twenty-two feet, and had brought to light the 

 fact that the deposit had been formed by a series 

 of dams one above the other, a new dam having 

 been built or the old one increased in height 

 when the deposit of sediment had rilled, or nearly 

 filled, the pond. This is only one instance. There 



are thousands of similar places in the Rockies 



66 



