DWELLINGS 1643 



"The great age of the larger dams is shown by; 

 their size, by the large amount of solid materials 

 they contain, and by the destruction of the primitive 

 forest within the area of the ponds ; and also by the 

 extent of the beaver-meadows along the margins of 

 the streams where dams are maintained, and by the 

 hummocks formed upon them by and through the 

 annual growth and decay of vegetation in separate 

 hills. These meadows were undoubtedly covered 

 with trees adapted to a wet soil when the dams were 

 constructed. It must have required long periods of 

 time to destroy every vestige of the ancient forest by 

 the increased saturation of the earth, accompanied 

 with occasional overflows from the streams. The 

 evidence from these and other sources tends to show 

 that these dams have existed in the same places for 

 hundreds and thousands of years, and that they have 

 been maintained by a system of continuous repairs. 



"At the place selected for the construction of a 

 dam, the ground is usually firm and often stony, and 

 when across the channel of a flowing stream, a hard 

 rather than a soft bottom is preferred. Such places 

 are necessarily unfavorable for the insertion of stakes 

 in the ground, if such were, in fact, their practice in 

 building dams. The theory upon which beaver-dams 

 are constructed is perfectly simple, and involves no 

 such necessity. Soft earth, intermixed with vegetable 

 fibre, is used to form an embankment, with sticks, 

 brush, and poles imbedded within these materials to 

 bind them together, and to impart to them the 

 requisite solidity to resist the effects both of pressure 

 and of saturation. Small sticks and brush are used, 



