34 COMMON BEAVER. 



one bank of the river to the other. The stakes 

 facing the under part of the river are placed per- 

 pendicularly ; but the rest of the work slopes up- 

 wards to sustain the pressure of the fluid, so that 

 the bank, which is ten or twelve feet wide at the 

 base, is reduced to two or three at the top. It 

 has, therefore, not only the necessary thickness 

 and solidity, but the most advantageous form for 

 supporting the weight of the water, for prevent- 

 ing its issue, and for repelling its efforts. Near 

 the top or thinnest part of the bank they make 

 two or three sloping holes, to allow the surface- 

 water to escape, and these they enlarge or con- 

 tract, according as the river rises or falls ; and 

 when any breaches are made in the bank by sud- 

 den or violent inundations, they know how to 

 repair them as soon as the water subsides. 



te It would be superfluous, after this account 

 of their public work, to give a detail of their par- 

 ticular operations, were it not necessary, in a 

 history of these animals, to mention every fact, 

 and were not the first great structure made with a 

 view to render their smaller habitations more com- 

 modious. These cabins or houses are built upon 

 piles near the margin of the pond, and have two 

 openings, the one for going to the land, and the 

 other for throwing themselves into the water. 

 The form of the edifices is either oval or round, 

 some of them larger, and some less, varying from 

 four or five, to eight or ten feet diameter. Some 

 of them consist of three or four stories, and their 

 walls are about two feet fhick, raised perpendicu- 



