90 THE AMERICAN BEAVER. 



that the dam at this point was commenced, as near 

 the ends, with brush and poles laid horizontally, but 

 lengthwise with the current, and filled in with earth 

 and mud intermixed with roots and grass, and that 

 as the work advanced, the upper ends became im- 

 bedded and concealed from view, while the lower 

 projected be3^ond the embankment. In course of 

 time, by the process of enlargement and repair, it 

 would assume its present form as shown in the engrav- 

 ing. With its increase in height, the crest of the 

 dam would tend to draw down stream from a line 

 perpendicular with the original centre of its base. In 

 consequence of this, the open stick and pole work, 

 which forms the face of the dam, advances upward 

 and under the water of the pond as you descend ver- 

 tically from its crest to the bottom of the structure. 

 None of the poles on the fnce of the dam at the great 

 curve were as long as the slope itself. They appeared 

 to be loosely thrown together, but on attempting to 

 raise a number of them they were found to be fast at 

 one end or the other, or so interlaced that it was dif- 

 ficult to remove them. 



It will be observed that the dam, at the place 

 where the greatest strength was required, is in the 

 form of a curve, with its curvature up stream, and 

 that the line of this curve is more than a hundred 

 feet in length. The use of the curve in beaver dams 

 is of very common occurrence, and it has always been 

 regarded as a striking evidence of the intelligence of 

 its builders. In the engraving its form does not dis- 

 tinctly appear, from the reduced scale upon which 

 the work is shown, but when the original photograph 

 is placed in a camera of large magnifying power, the 



