RODENTIA. 



517 



The Beavers (Castor) are distinguished from all 

 other Rodents by their tail, which is horizontally 

 flattened, of a nearly oval form, and covered with 

 scales. They have five toes on every foot, and those 

 of the hinder feet are webbed. 



The Beaver (Castor Fiber*) is an inhabitant of the most solitary 

 parts of North America. It is also met with in Siberia and 

 Norway. These animals are always found in the vicinity of rivers 

 and lakes; in the summer they inhabit burrows, which they dig 

 along the shores, but hi winter they retire into huts, constructed 

 with the greatest care, on the banks or in the midst of the water. In 

 constructing these habitations they generally choose the deepest 



FlG. 4-13. BEAVER. 



pools, which are not likely to be frozen to the bottom ; and 

 they prefer running streams, which enable them to cut the wood 

 necessary for then* building above the spot where they work, and 

 then the current carries it where it is required. If the waters are 

 stagnant they at once commence their houses, but if it is running 

 they assemble together, often two or three hundred in a gang, and first 

 form a shelving dam or dyke to maintain the water at an equable 

 height. This dam is formed of branches interlaced with each other ; 

 the intervals between them being filled with stones and mud, and 

 plastered over with a thick solid coat. It is commonly ten or twelve 

 feet thick at the base, and is sometimes of very considerable extent, 

 so that at the expiration of a few years it is usually covered with 



