HYBERNATION. 115 



rupted hybernation, to which latter, brief 

 hybernation belongs rather than to the former. 

 We may now, therefore, advert to that third kind 

 of hybernation previously alluded to, during 

 which sleep beyond what all quadrupeds 

 ordinarily require, is either not at all expe- 

 rienced, or only in a degree so trifling as not 

 to have attracted especial notice. The beaver 

 shall be first cited as affording an example in 

 point. The beaver is a gregarious animal of 

 semi-aquatic habits. During the summer, the 

 beavers composing a colony roam about at 

 pleasure, and it is during that season that they 

 fell the wood necessary for repairing their 

 houses and dams, or for building others, com- 

 mencing the latter about the end of August. 

 The use of the dam is to secure a great depth 

 of water beyond the freezing power to congeal 

 at the bottom ;. where the water is of sufficient 

 depth a dam is not constructed. The houses 

 vary in size and in the number of lodging- 

 rooms. These rooms do not communicate with 

 each other, but each has a separate entrance 

 under the water. Like the dam, the houses 

 are constructed of wood, stones, and mud, and 

 during the winter the compact mass becomes 

 frozen as hard as stone. When complete, the 

 houses have a dome-like figure, with walls 

 several feet thick based upon the bed of the 

 river, and emerging from four to six feet above 

 the water. The only entrance is deep under 

 water, below a projection called by hunters the 

 angle, and consequently the water fills a great 



