HISTORY OF QUADRUPEDS. 413 



down with their teeth, such trees and branches as 

 suit them; these consist chiefly of green willows, 

 birch, and poplars, which, together with such drift 

 wood as they can meet with, their foresight directs 

 them to drag to the water with their teeth, and float 

 the whole down the stream to the place where it is 

 wanted: having thus provided a stock of materials, 

 the next operation, where an apprehended want of 

 water makes it necessary, is building the dam ; but 

 they do not fall to work upon this until about the 

 middle or latter end of August, when the timbers 

 are then laid in and bedded together across the 

 stream, with stones, earth, clay, and mud, which 

 they collect during the night, and carry between 

 their fore feet and their throat, with surprising 

 labour and perseverance. The dam or mound is 

 always made in an arched shape, of greater or 

 lesser convexity, according to the rapidity of the 

 stream ; it is of great strength and thickness, being 

 eight or ten feet at the. base, gradually tapering 

 upwards to near the top, of a height sufficient to 

 secure to them an abundance of water below the 

 reach of the frost, and is capable of sustaining a 

 great weight or pressure of that element. Having 

 completed the mole, their next care is, for each 

 family to erect their own habitations; these are 

 made of the same kind of materials, and are built at 

 a convenient distance above the dam, and are more 

 or less of a circular, or of an oblong form, both on 

 the sides and on the top, and are at first about two 

 feet in thickness, but strengthened on the sides, and 

 heightened on the top by different plasterings, 

 every season, to about eight feet high, and the last 

 plastering is not put on until the frost sets in with 

 severity, by which it is rendered impenetrable to 



