THE BEAVER. 165 



water is liable to be drained off when the back supplies 

 are dried up by the frost, they are led by instinct to 

 make a dam quite across the river at a convenient dis- 

 tance from their houses, thus artificially procuring a 

 deep body of water in which to build. The dam varies 

 in shape. Where the current is gentle, it is carried out 

 straight ; but where rapid, it is bowed, presenting a con- 

 vexity to the current. The materials used are drift- 

 wood, green willows, birch, and poplar, if they can be 

 got, and also mud and stones. These are intermixed 

 without order, the only aim being to carry out the work 

 with a regular sweep and to make the whole of equal 

 strength. 



"'Old dams by frequent repairing become a solid 

 bank, capable of resisting a great force of water and 

 ice ; and as the willows, poplars, and birches take root 

 and shoot up, they form by degrees a sort of thick 

 hedgerow, often of considerable height. Of the same 

 materials the houses themselves are built, and in sizes 

 proportioned to the number of their respective inhabit- 

 ants, which number seldom exceeds four old and six or 

 eight young ones. 



" ' The houses are ruder in construction than the dam, 

 the only aim being to have a dry place to lie upon, and 

 perhaps to feed in. 



" ' When the houses are large, it often happens that 

 they are divided by partitions into two, or three, or 

 even more apartments, which in general have no com- 

 munication with each other except by water ; such may 



