272 NATURAL HISTORY. 



with which it is built is still more astonishing than its- 

 size. The part of the river over which this dam is 

 usually built, is where it is most shallow, and where 

 some great tree is found growing by the side of the 

 stream ; this they make choice of for the principal 

 part in their building ; and, though it is often thicker 

 than a man's body, they soon cut it down. For this 

 operation they have no other instrument than their 

 four incisive teeth, with which they make it fall al- 

 ways across the stream; they then set about cutting 

 the top branches, to make it lie close and even, and 

 serve as the principal beam for their fabric. 



These operations are performed in common. At 

 one time a number of beavers are employed together 

 at the foot of the tree in gnawing it down ; and, when 

 this part of their labour is finished, it becomes the busi- 

 ness of others to separate the branches, while a third 

 party are engaged along the banks of the river, or lake, 

 in cutting other trees, which, though smaller than the 

 first, are yet as thick as the leg, if not the thigh, of a 

 common sized man. These they carry with them by 

 land to the brink of the river, and then by water to the 

 place allotted for their building ; where, sharpening 

 them at one end, and forming them into stakes, they 

 drive them into the ground, at a small distance from 

 each other, and fill up the vacant spaces with pliant 

 branches. While some are thus employed in fastening 

 the stakes, others go in search of clay, which they 

 prepare for their purpose with their tails and their feet, 

 and with which, they render their structure still more 

 compact. 



This structure is so ingeniously contrived, that it 

 has not only all the extent, and all the solidity, which 

 are requisite, but also a form the most proper for con- 



