360 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, for the 

 beavers to move them for any considerable 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 afiford 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 happens 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 



