230 THE INDUSTRIES OF ANIMALS. 



such necessity. Soft earth, intermixed with vegetable 

 fibre, is used to form an embankment, with sticks, 

 brush, and poles embedded within these materials to 

 bind them together, and to impart to them the 

 requisite solidity to resist the effects both of pressure 

 and of saturation. Small sticks and brush are used, 

 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 

 discharged 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 



' L. H. Morgan, The American Beaver and his Works, Philadelphia, 

 1868, pp. 82-86. 



