BEAVER DAMS. 95 



whole extent, dimmishing from a few inches at its 

 widest expanse to a mere line. It is a conspicuous 

 feature of beaver dams of this class that they are so 

 perfectly constructed as to hold and retain water until 

 it rises to their very summit. A fine sod, composed 

 of roots of grass intermixed with loam, is used to 

 finish the water line of the dam. On taking up a 

 handful of this sod, freeing it from earth and rinsing 

 it clean, it yielded one-half of its original bulk of 

 vegetable fibre, mostly fine roots and tendrils, still 

 green and undecayed. It was thus made evident 

 that it had been quite recently laid. 



In constructing dams, loose stones are incorporated, 

 here and there, for down weight, and to give solidity 

 to the structure. We found stones upon this dam 

 which would weigh from one to six pounds. They 

 are most frequently discovered where the dam is the 

 lowest, although found in all parts of the work. 



No one standing upon this dam, and observing its 

 fragile character, could fail to perceive that its main- 

 tenance would require constant supervision and per- 

 petual labor. The tendency to increased leakage 

 from the effects of percolation, and to a settling down 

 of the dam, as its materials decayed underneath upon 

 its stick-work half, would demand unceasing vigilance 

 and care to avert the consequences. In the flxU of 

 the year a new supply of materials is placed upon the 

 lower face of these dams to compensate this waste 

 from decay. They use for this purpose the cuttings of 

 the previous fall, which during the winter have been 

 stripped of their bark for food, and laid aside appar- 

 ently for this object. It is from this practice, and the 



