1644 THE STORY OF THE UNIVERSE 



in the first instance, with mud and earth and stones 

 for down-weight. Consequently these dams are ex- 

 tremely rude at their commencement, and they do 

 not attain their remarkably artistic appearance until 

 after they have been raised to a considerable height, 

 and have been maintained, by a system of annual 

 repairs, for a number of years."* 



There are two different kinds of beaver-dams, 

 although they are both constructed on the same 

 principle. One, the stick-dam, consists of interlaced 

 stick and pole work below, with an embankment of 

 earth raised with the same material upon the upper 

 or water face. This is usually found in brooks or 

 large streams with ill-defined banks. The other, the 

 solid-bank dam, is not so common nor so interesting, 

 and is usually found on those parts of the same 

 stream where the banks are well defined, the channel 

 deep, and the current uniform. In this kind the 

 earth and mud entirely buries the sticks and poles, 

 giving the whole a solid appearance. In the first 

 kind the surplus water percolates through the dam 

 along its entire length, while in the second it is dis- 

 charged through a single opening in the crest formed 

 for that purpose. 



The materials being prepared in the manner I have 

 previously described, the animals make ready to 

 establish their dike. They intermix their materials 

 driftwood, green willows, birch, poplars, etc. in 

 the bed of the river, with mud and stones, so making 

 a solid bank, capable of resisting a great force of 



* L. H. Morgan, The American Beaver and his Works, Phil- 

 adelphia, 1868, pp. 82-86. 



