THE BEAVERS OF NORTH AMERICA 31 



stand and account for what they do if we would 

 only start out with the idea that both animals and 

 birds, though governed by certain very definite laws, 

 have the use of a limited free intelligence, which 

 enables them to take advantage of conditions and 

 accomplish things which are apparently not in 

 keeping with what might be done by others of the 

 same species. It is this individuality which helps 

 animals to adjust themselves to new conditions, 

 whereas if they adhered too strictly to the rules 

 which have governed them in the past they would, 

 through the lack of power of free thought, fall easy 

 victims to new and adverse conditions. 



Having now seen what the beaver's lodge is like, 

 we may take into consideration the dam which is 

 the direct adjunct to the house or rather to the 

 more advanced type of house. Just when or how 

 dams first began it is impossible for us to say, but 

 the chances are they are the result of a very gradual 

 development through perhaps thousands of years. 

 So far as I can learn the beaver of the old world 

 did little or no important dam building, but his 

 close cousin on the American continent has without 

 doubt been building them for a very long time 

 and with some very extraordinary results. (These 

 will be dealt with in another chapter.) 



As already stated the primary objects of the 

 dams appear to be four-fold, the most important 

 being apparently that water may be maintained 

 at a constant level in order that the house shall 



