MAMMALIA—BEAVER. 2235 
Atashort distance above a beaver dam, the number of trees which have 
been cut down, appears truly surprising, and the regularity of the stumps 
which are left, might lead persons unacquainted with the habits of the 
animal to believe that the clearing was the result of human industry. 
“The figure of the dam varies according to circumstances. Should the 
current be very gentle, the dam is carried nearly straight across; but when 
the stream is swiftly flowing, it is uniformly made with a considerable 
curve, having the convex part opposed to the current. Along with the 
trunks and branches of trees, they intermingle mud and stones, to give 
greater security ; and when dams have been long undisturbed and frequently 
repaired, they acquire great solidity, and their power of resisting the pres- 
sure of water and ice, is greatly increased by the willow, birch, &c., occa- 
sionally taking root, and eventually growing up into something of a 
regular hedge. The materials used in constructing the dams, are secured 
solely by the resting of the branches, &c., against the bottom, and the sub- 
sequent accumulation of mud and stones, by the force of the stream, or by 
the industry of the beavers. 
“The dwellings of the beaver are formed of the same materials as their 
dams, and are very rude, though strong, and adapted in size to the number 
of their inhabitants. These are seldom more than four old, and six or eight 
young ones. Double that number have been occasionally found in one of 
the lodges, though this is by no means a very common occurrence. 
“When building their houses, they place most of the wood cross-wise, and 
nearly horizontally, observing no other order than that of leaving a cavity in 
the middle. Branches, which project inward, are cut off with their teeth and 
thrown among the rest. The houses are by no means built of sticks first, 
and then plastered, but all the materials, sticks, mud, and stones, if the 
latter can be procured, are mixed up together, and this composition is 
employed from the foundation to the summit. The mud is obtained from 
the adjacent banks or bottom of the stream or pond, near the door of the 
hut. Mud and stones, the beaver always carries, by holding them between 
his fore paws and throat. 
“Their work is all performed at night, and with much expedition. When 
straw or grass is mingled with the mud used by them in building, it is an 
accidental circumstance, owing to the nature of the spot whence the latter 
was taken. As soon as any part of the material is placed where it is in- 
tended to remain, they turn round and give it a smart blow with the tail. 
The same sort of blow is struck by them, upon the surface of the water. 
when they are in the act of diving. 
“The outside of the hut is covered, or plastered with mud, late in the 
autumn, and after frost has begun to appear. By freezing, it soon becomes 
almost as hard as stone, effectually excluding their great enemy, the wolve- 
rene, during the winter. Their habit of walking over the work frequently 
luring its progress, has led to the absurd idea of their using the tail asa 
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