400 QUADRUPEDS. 



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 in 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 gene- 

 rally choose the deepest 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 their 

 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 



, 



,, 



~ x <TTan?Mnu.r ' '* " 



FIG. 443. BEAVER. 



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 vegetation, and thus converted 

 into a substantial hedge. The dam being finished, they separate into small parties, 

 and set about the construction of their huts, which are built against the dam, but with 

 less solidity. Each hut accommodates two or three families ; it has two storeys, the 

 upper one being dry, for the residence of the animals, the lower one under water, for the 

 store of bark upon which they feed. The entrance to this habitation is always under 

 water. Their work is carried on in the night only, but with astonishing rapidity. 



The Rats (Mus}. This extensive genus is composed of a great number of 

 small Rodents, which resemble our common rats in the most important points 

 of their economy. Their front paws have generally four toes and a tubercle 

 representing a thumb ; the hinder feet have five complete toes. Most of them 

 live in holes. The species are very numerous : amongst them we can only 

 notice 



The Musk-Rat of Canada (Mns Zibdicus], of the size of a rabbit, and of a 

 reddish-grey colour. These animals in winter construct a hut of clay on the ice, where 

 they live in great numbers. 



