584 ZOOLOGY. 
plateaus of Scandinavia down and into the sea; the object 
and origin of which are inexplicable, and are not indicative 
of much intelligence. From this and their nest-building 
habits, rodents are, as a rule, not unlike birds ; and Owen, for 
these reasons, ascribes to them a low degree of intelligence. 
Granting that this is the case, an exception to this rule is 
seen in the social beavers, which evince a high, exceptional 
degree of intelligence. Beavers build a dam in a running 
stream so as to create an artificial pond as a refuge when at- 
tacked, as well as a subaquatic entrance to their lodges and to 
their burrows in the banks of the streams they inhabit. Bea- 
ver 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. 
Beavers lay up stores of wood for winter use in the autumn; 
they can gnaw through trees eighteen inches in 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 
intelligence performed by beavers.” When ponds do not 
reach hard-wood trees or ground in which 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 con- 
nection, by water, with the trees that supplied them with 
food, as well as to relieve them from the tedious, and per- 
haps impossible, task of moving their cuttings five hundred 
feet over uneven ground, unassisted by any descent.” Bea- 
vers, in swimming, use their tail as a scull, and the hind 
feet being webbed, its propelling 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 to “‘ give it a throw forward.” Beavers are very 
social, working together and storing up wood in common. 
“‘A beaver family consists of a male and female, and their 
offspring of the first and second years, or more properly, 
