380 
ANIMAL INTELLIGENCE. 
Where the pond fails to accomplish this fully, and also 
where the banks are defined and mark the limits of the 
pond, the deficiency is supplied by the canals in question. On 
descending surfaces, as has elsewhere been stated, beavers roll 
and drag their short cuttings down into the ponds. But 
where the ground is low it is generally so uneven and rough 
as to render it extremely difficult, if not impossible, fot* the 
' beavers to move them for any cons' derable distance by physical 
force. Hence the canal for floating them across the inter- 
vening level ground to the pond. The necessity for it is so 
apparent as to diminish our astonishment at its construction ; 
and yet that the beaver should devise a canal to surmount this 
difficulty is not the less remarkable. 
The canals, which are made by excavation, are usually 
from three to five feet wide, three feet deep, and perhaps 
hundreds of feet long — the length of course depending on 
the distance between the lodge and the wood supply. They 
are cut in the form of trenches, having perpendicular sides 
and abrupt ends. All roots of trees, under-brush, &c„ 
are cleared away in their course, so as to afford an un- 
obstructed passage. These canals are of such frequent 
occurrence that it is impossible to attribute them to acci- 
dent ; they are evidently made, at the cost of much labour, 
with the deliberate purpose of putting them to the use for 
which they are designed. In executing this purpose there 
is sometimes displayed a depth of engineering forethought 
over details of structure required by the circumstances of 
special localities, which is even more astonishing than 
the execution of the general idea. Thus it not unfre- 
quently happ&is that when a canal has been run for a 
certain distance, a rise in the level of the ground renders 
it impossible to continue the structure further from the 
water supply or lodge-pond, without either incurring a 
great amount of labour in digging the canal with pro- 
gressively deepening sides, or leaving the trench empty of 
water, and so useless. In such cases the beavers resort to 
various expedients, according to the nature of the ground. 
Mr. Morgan gives an interesting sketch of one such 
case, where the canal is excavated through low ground for 
a distance of 450 feet, when it reaches the first rise of 
