I 9 2 THE PSYCHICAL KINSHIP 



being regularly lessened and enlarged to suit the 

 supply of water in the stream. The trees used by 

 the beavers in their enterprises are felled by them 

 along the margins of the stream, and floated to 

 the place where they are used. In old com- 

 munities, where the supply of timber near the 

 stream has been exhausted, artificial canals are 

 cut by these indomitable engineers for use in the 

 transportation of their materials. These excava- 

 tions are made at a great cost of labour and for 

 the deliberate purpose of enabling the builders to 

 accomplish that which they could not accomplish 

 in any other way. ' In executing this purpose,' 

 says Romanes, ' there is sometimes displayed, a 

 depth of engineering forethought over details of 

 structure required by the circumstances of special 

 localities which is even more astonishing than the 

 execution of the general idea* (10). When, for 

 instance, a canal has been carried so far from the 

 original water-supply that, owing to the rising 

 ground, it cannot be continued without a very 

 great expenditure of effort in digging, a second 

 dam is built higher up-stream, and with water 

 drawn from this the canal is continued on at 

 a higher level. Sometimes a third dam is built 

 above the second, and the canal again continued 

 at a still higher level before the valuable timber of 

 the higher grounds is reached. These enterprising 

 rodents also carve sometimes enormous channels 

 across the necks of land formed by winding rivers, 

 to serve as cut-offs in travel and transportation. 

 And yet all of these things all of the intelli- 



