702 RODENTIA. 



THE AMERICAN BEAVER. 



The American Beaver, Castor Canadensis (Plate LV), is distinguished 

 from its European congener by its more arched profile, its narrower 

 head, and its darker coat. It is a social animal, and displays a singular 

 mixture of reason and instinct. The societies in which it lives vary 

 considerably in numbers ; they dwell near small clear rivers and creeks, 

 or close to large springs, rarely taking up their abode on the banks of 

 lakes. In such situations it executes works which would do credit to 

 any engineer. The object of these works is to keep the water always 

 above the level of the entrance-tunnel which leads to its house. The 

 dams constructed for this purpose are formed of tree-branches, mud, and 

 stones ; they are ten or twelve feet thick at the bottom, and about two 

 feet at the top ; in length they vary, some attaining the dimensions of 

 two or three hundred feet. When the stream to be stopped is gentle, 

 the dam is carried straight from bank to bank ; when it is impetuous, the 

 dam is curved upward against the stream. The logs forming the dam 

 are laid horizontally, and kept down by stones ; they are about three 

 feet in length, and vary extremely in thickness. Generally, they are 

 about six or seven inches in diameter, but they have been known to 

 measure no less than eighteen inches in diameter. An almost incredible 

 number of these logs are required for the completion of one dam, as may 

 be supposed from the fact that a single dam will sometimes be three hun- 

 dred yards in length, ten or twelve feet thick at the bottom, and of a 

 height varying according to the depth of water. Before employing the 

 logs in this structure, the Beavers take care to separate the bark, which 

 they carry away, and lay up for a winter store of food. 



Near the dams are built the Beaver-houses, or " lodges," as they are 

 termed ; edifices as remarkable in their way as that which has just been 

 mentioned. They are entirely composed of branches, moss, and mud. 

 and will accommodate five or six Beavers together. The form ot an 

 ordinarily sized Beaver's lodge is circular, and its cavity is about seven 

 feet in diameter by three feet in height. The walls of this structure are 

 extremelv thick, so that the external measurement of the same lodges 

 will be fifteen or twenty feet in diameter, and seven or eight reet in 

 height. The roofs are all finished off with a thin layer of mud, ,/aid on 

 with marvelous smoothness, and carefully renewed every year. As this 

 compost of mud, moss, and branches is congealed into a solid mass by 



