BEAVER-HOUSES. 149 



of climate and locality, or more probably in the nature of the 

 waters, may be the cause of this change in habit. 



I have dug up many beaver-houses, both to recover 

 traps and to obtain a knowledge of their construction. 

 It has always been a work of considerable labour to do 

 so, on account of osier, willow, and other trees growing 

 on the banks of the streams, and of the rocks and 

 stones in the ground. Their construction I have invari- 

 ably found to be the same in all essential particulars ; 

 their locality, the banks of the pool made by their dam, 

 and for a very good reason. It is essential to the comfort 

 of the beavers that the water in their houses should be 

 always at about the same level. To ensure this during 

 an unusual flood, they partially but sufficiently break the 

 dam. 



The entrance to these houses is about a foot under 

 water, and is a round hole in the bank of the stream. 

 This hole is about nine or ten inches across, and runs 

 back into the bank from four to ten feet, according to 

 the soil and other circumstances. At its termination is 

 a circular basin, generally about four feet across and as 

 many deep, and having a vaulted roof a foot or so above 

 the level at which the water stands. This is the beaver's 

 winter bath-room, its depth below the surface of the 

 ground (the bank of the river being any number of feet 

 high), and its distance back ensuring that the water in it 

 will remain unfrozen. Radiating from this vaulted chamber 

 as a centre, and sloping upwards, often for many feet if the 

 stream is liable to great floods, are passages leading to 

 dwelling, breeding, and store-rooms. How ventilation is 



