BEAVER DAMS. 101 



I have now given a full as well as somewhat de- 

 tailed description of a beaver dam of the ordinary 

 kind constructed by this architectural mute. This 

 explanation, and the engravings together, will render 

 unnecessary a special description of other dams of the 

 same class. In the remaining dams noticed, I shall 

 limit the description to the special features or differ- 

 ences by which they are distinguished, giving, at the 

 same time, ground plans and measurements for the 

 purpose of comparison. 



New dams are occasionally commenced, and old 

 ones, previously abandoned for some cause, are re- 

 paired and reoccupied, in beaver districts which are 

 undisturbed except by trappers. The increase or 

 decrease of beavers in number's, influences, to some 

 extent, their movements in these respects. The sea- 

 son preferred for this work is during the months of 

 September and October, after the strong currents have 

 run out of the streams, and they have subsided to 

 their lowest levels. It is also the period during which 

 they cut and store their winter wood, with the im- 

 mersion and safety of which their ponds are intimately 

 connected. Hence we find that the active season for 

 beaver work is late in the fall; and that it is per- 

 formed with reference to the approaching winter, of 

 which they are not unmindful. These vseveral subjects 

 will be elsewhere considered. 



For the purpose of ascertaining how beaver dams 

 are commenced, and especially to find whether an 

 attempt is made to insert any portion of the materials 

 in the ground, as a means of holding them in their 

 places, I have taken up to the bottom both old and 

 new beaver dams, and examined, with some care, the 



