44 ROMANCE OF THE BEAVER 



chosen proves entirely satisfactory it will continue 

 to grow as the years go on, each year seeing the 

 extending of the dam, and, if necessary, the number 

 of subsidiary dams increased. The trees whose 

 base has been flooded by the rising water gradually 

 die, and the gaunt grey columns bear witness to the 

 effect that beavers' work has on the land. So long 

 as the supply of suitable food trees is to be found 

 the colony remains, unless killed off or driven oft 

 by the trappers, and so it is that such immense 

 dams are found, some over two thousand feet in 

 length with a height of from two to about fourteen 

 feet, the result of countless generations of indus- 

 trious beavers, not necessarily working continuously, 

 for they often abandon a pond for many years, 

 apparently to give time for the food trees to grow. 

 On their return, or if a new colony takes possession, 

 they have a busy time repairing the dam and 

 getting everything in proper order. 



The solidity of the structures is perhaps best 

 proved by the fact that some have been found in 

 Montana which were in a partially petrified state. 

 As a rule, however, the life of a dam is but 

 a few years beyond the period during which it is 

 used ; owing to the nature of the material employed^ 

 constant supervision and repair are absolutely neces- 

 sary. The beaver realise this and seldom allow 

 a night to pass, during the autumn, without 

 making a tour of inspection and building up 

 and strengthening any part that shows signs of 



