140 THE AMERICAN BEAVER. 



reasons for believing that the burrow is the normal 

 residence of the beaver; and that the lodge grew out 

 of it, in the progress of their experience, by natural 

 suggestion. This subject will be referred to again. 

 We have before seen that one of the principal objects 

 of the dam was the formation of a pond; thus show- 

 ing a desire, on the part of its architects, to maintain 

 a large body of water at a permanent level for some 

 special use. We come now to inquire its uses, so far 

 as they relate to the lodge and the burrow. There 

 are several varieties of the beaver lodge, each of which 

 is adapted to the peculiarities of its situation; but 

 they collectively represent different applications of 

 the same general principle of construction. Thus we 

 find an island, a river bank, and a lake lodge, each 

 of which has special characteristics. The same is 

 true, in a less degree, of their burrows. Each will be 

 considered in its order. 



Where large ponds are formed by means of dams, it 

 is not unusual to find small grass islands rising a few 

 inches above the level of the water. These islands 

 were probably produced by fallen trees which had 

 been flooded and destroyed by the pond, and upon the 

 decayed remains of which vegetation had sprung. 

 In other cases there are islands of firm earth which 

 chanced to rise naturally above the surface of the 

 water. These, whether unsubstantial or firm, are 

 generally selected as the sites for their lodges because 

 of the additional protection which insulation affords. 



The lodge represented in the engraving (Plate XIII.) 

 is situated upon one of the low grass islands described, 

 and is one of the two found in Grass Lake above the 

 great dam. As it was engraved from a photograph, it 



