94 THE AMERICAN BEAVER. 



made impenetrable, the water would rise and flow 

 over its crest, to its waste and injury. At ordinarj^ 

 stages of the water the pond is maintained at a uni- 

 form level; but after a sudden rise, or in time of 

 freshet, it flows over the summit. The structure is 

 better able to bear an overflow than rents through its 

 embankment. This dam was rarely if ever over- 

 flowed, for a special reason, which will be stated 

 hereafter. Those upon the Carp, however, are sub- 

 merged with every considerable rise of the stream, 

 which, having a wide drainage, is subject to sudden 

 freshets. I have seen the water run over the tops of 

 these dams a foot deep. After the flow subsided, the 

 rents were speedily repaired. At ordinary stages the 

 surplus water passed through the dams by percola- 

 tion, straining through them near the crest as though 

 they were fine basket-work. I have visited the 

 Grass Lake dam six difierent years, and at high and 

 low stages of the water in the neighboring streams, 

 and always found the pond at the same level, and 

 full to the crest of the dam, until the year 1865, 

 when it was lower than usual, and the dam itself 

 exhibited signs of neglect. From this fact it seemed 

 probable that after centuries of use and maintenance 

 by unnumbered generations of beavers, this interest- 

 ing and remarkable structure was about to be aban- 

 doned by its natural proprietors. 



At the time the photograph was taken, the water of 

 the pond stood quite near the summit of the dam 

 along its entire length. In some places it came within 

 one or two inches, while in others it stood upon it and 

 trickled over. The crest is very narrow along its 



