48 ROMANCE OF THE BEAVER 
prevailing conditions. In the photograph there 
is an example of how cleverly the small creatures 
utilised an immense boulder in the middle of a 
rapid flowing stream. Rocky bedded waterways 
offer many and serious difficulties to the beavers, 
for it is hard to get anchorage, and in this 
particular case the current was so swift that te 
build a successful dam required unusual skill 
Evidently the beaver made a thorough investiga- 
tion of the little river and finally selected what 
was about the only reasonably good place for their 
operations. The large boulder acted as a support 
or anchor for their work (this can be plainly seen in 
the photograph), so that when the structure, which , 
was over four feet high, was finished, it resisted 
the flow of water and formed a fair-sized pond and 
an island on which the beaver built their lodge. 
Some writers have claimed that the animals’ 
begin their dams by felling a large trée across the . 
stream. This may be true, but I have never seen | 
an instance of it. What does often happen is that . 
a fallen tree lying across a stream suggests a good 
position for the dam, or a floating log carried down ° 
during the spring thaws becomes lodged against 
the stream banks so that the beaver take advantage 
of it and build against it. Except under conditions . 
of this kind it is unusual to find the timber, whether 
stick, brush or log, placed so that it lies in any 
way but with the course of the stream. This is 
reasonable enough when we consider how little 
