BEAVER CANALS, MEADOWS, AND TRAILS. 193 



beavers roll and drag their short cuttings down into 

 the ponds. But where the ground is low, it is gener- 

 ally so uneven or rough as to render it extremely dif- 

 ficult, if not impossible, for the beavers to move them, 

 for any considerable distance, by physical force. 

 Hence the canal for floating them across the inter- 

 vening level ground to the pond. The necessity for it 

 is so apparent as to diminish our astonishment at its 

 construction; and yet that the beaver should devise 

 a canal to surmount this difficulty is not the less 

 remarkable. 



The area represented by the map is not more 

 abundantly supplied with dams, lodges, and burrows 

 than with artificial canals. It contains within its 

 limits nearly every variety of the works of the 

 beaver found in North America, some of which, as 

 the Grass Lake dam, are unequaled in their magni- 

 tude and completeness. Beaver canals are very nu- 

 merous within this area. Many of them are small 

 and unimportant; but the great length of some of 

 them is the striking feature which invests them, as 

 artificial works, with a high degree of interest. 



Immediately north of the Cleveland Iron Mine there 

 is a natural pond (Plate XVII.) covering about forty 

 acres of land. It is bordered on all sides, except at its 

 outlet, with rising ground at the distance of a few hun- 

 dred feet from its margin. The intermediate ground is 

 level, and rises but a few inches above the surface of 

 the pond. On this low land there is first a border of 

 moss turf entirely skirting the pond, and spreading 

 out in different places from fifty to two hundred or 

 more feet. Without this, tamarack, spruce, and pine 

 are found; and upon the rising ground, birch, ash, and 



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