254 ZOOLOGY. 



artificial pond as a refuge when attacked, as well as a sub 

 aquatic entrance to their lodges and to their burrows in 

 the banks of the streams they inhabit. Beaver dams are 

 built at first by a single pair or family, and are added to 

 from year to year, and afterwards maintained for centuries 

 by constant repairs. They are built of sticks and mud, 

 usually curve up stream, with a sloping water-face. Beav- 

 ers lay up stores of wood for winter use in the autumn; 

 they can gnaw through trees eighteen inches m diameter; 

 they work mostly at night. They often construct artificial 

 canals for the transportation of the sticks of wood to their 

 lodges. This, in the opinion of Mr. Morgan, " is the 

 highest act of intelliger.ee performed by beavers." When 

 ponds do not reach hard-wood trees or ground in which 



Fig. 294.— Sewellel or Showtl. Much reduced. 



they can burrow for safety, they will build canals with 

 dams, and so excavate them that they will hold the surface 

 drainage. Morgan describes one canal about 161 metres 

 (523 feet) long which "served to bring the occupants of 

 the pond into easy connection, by water, with the trees 

 that supplied them with food, as well as to relieve them 

 from the tedious, and perhaps impossible, task of moving 

 their cuttings five hundred feet over uneven ground, unas- 

 sisted by any descent." Beavers, in swimming, use their 

 tail as a scull, and the hind feet being webbed, its propel- 

 ling power while swimming is very great. They carry 

 small stones and earth with their paws, holding them 

 under the throat, and walking on their hind feet. They 

 use the tail in moving stones, working it under so as tc 



