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WARREN 



veying the extensive new work nearest the town, I carried the 

 survey up the river quite a distance, as shown on the map (Plate 

 xxv). In making the survey I did not have time to go as far as 

 I wished. There were some interesting things still farther up, 

 both in the river and in some of the sloughs which should have 

 been included. 



At low water the river varies in width from 20 to 40 feet. 

 During high water, at the time of melting snows in spring and 

 early summer, it is much higher and through this level ground 

 must often overflow its banks. The area covered by the accom- 

 panying maps (Plates xxv and xxvi) comprises many sloughs 

 and channels, varying in width from i to 15 feet, and averaging 

 perhaps from 2 to 4 feet. No attempt was made to trace out all 

 the channels, only those most closely connected with the beavers' 

 work being shown. 



Considering the area covered by the larger scale map (Plate 

 xxv) first, it will be noted that with the exception of the 2 dams 

 across the river, all the work done is to the south of the stream, 

 and consists, besides houses, of many dams, most of them small, 

 though I or 2 are of considerable length. Altogether they 

 flood an area some 1,500 feet from east to west which contains 

 about 17 acres. 



The reason there are no works north of the river is that the 

 beavers completed their work there many years ago, raising 

 practically all the land on that side above high water mark and 

 converting it into a meadow, now much overgrown with willows. 



The lower dam across the river was 76 feet in a straight line 

 from end to end, but it is curved twice (Plates xxv and xxvii) 

 and does not reach all the way to the left bank. Below this 

 dam, and setting out diagonally into the stream from the left 

 bank, is a short dam, 20 feet long, so that the water flows around 

 the end of the long upper dam and then around the free end of 

 the short lower one, which thus throws the main body of water 

 back to the right bank where it would naturally flow if undis- 

 turbed by obstructions. The explanation of these curves and 

 dams is that at this place the right bank is higher and the water 

 deeper than on the opposite side, so that the downward curve 

 at the southerly end of the long dam creates an eddy and back 



