EDWARD BURGESS. 69 



long was constructed which effectually shut in the waters 

 so as to maintain them at the proper elevation. The 

 entire dam, including the natural barriers which had to 

 be filled in in places, was 1,630 feet long. . 



It often happens that the pressure of water against a 

 dam is so great as to endanger its stability. To obviate 

 this, the beavers build another dam, a short distance 

 below the main one, raising the water a foot or a foot 

 and a half, which backing up against the larger one, 

 diminishes to this extent the differences in the level 

 above and below, and thus neutralizes the pressure of 

 the water against the main structure. They have been 

 known also to build a dam above the main one, for the 

 purpose of keeping back the water in time of freshet, 

 which but for this, the main outlet could not safely 

 carry off. 



These dams serve another and very important purpose, 

 beside keeping the water at a certain level for the 

 "lodges" and "burrows," and that is by flooding the 

 surrounding area, bring the water line up to the hard 

 wood trees, upon which they feed, so that these can be 

 carried to their lodges by water transportation. This is 

 a very important consideration, for the labor of dragging 

 the wood over the ground is very great, and when there 

 is no incline and the ground rough, almost impossible. 

 But even this raised area becomes denuded in time, and 

 then to save land carriage, the beaver resorts to the 

 extraordinary device of digging canals, which penetrate 

 into the hard wood region, affording a water way for 

 bringing out the wood. These canals are from three to 

 five feet wide, about three feet deep and hundreds of 

 feet long, and are made by excavation. All roots and 

 stumps of trees are carefully removed, so as to form a 

 free and unobstructed way. 



Mr. Morgan observed one that extended 450 feet on a 

 level with the pond that supplied it with water. Here 



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