34 THE BEAVER 
complete and final state of petrifaction which involves the 
change of every particle of the original woody materials, and 
the substitution of solid substances; but rather incrusted 
with lime, which, penetrating and solidifying the entire 
structures, had given them a permanently durable form.” 
These dams were fifty to sixty feet long, and had a fall of 
water over them of from one to four feet. 
The beaver has been credited with having the intelligence 
to build its dam with an upstream curve, the better to 
withstand the force of the current. Just another of the 
legends about the animal. Sometimes the dams are built in 
a straight line across the stream, sometimes curved up and 
sometimes down, and in a long dam often bent both ways 
indiscriminately. I think they do this without any special 
reasoning, unless special circumstances force a particular 
construction. ‘The most peculiar example of a downstream 
curve which I have seen was on a dam on a small stream in 
Colorado. When I first saw it I called it a ‘‘mule-shoe 
curve.” I examined and measured it. The total length 
was seventy-one feet. From the end at the right bank of 
the stream it extended down parallel with the current 
twenty-four feet. At this point high water had torn a 
gap five feet wide and swung the broken-out portion down- 
stream in line with the other part. It was twelve feet across 
at right angles to the stream to where the dam turned up 
again, and it was about twenty-five feet across between the 
two ends of the dam. I could see no reason for this manner 
of construction. There did not appear to have been any 
obstacle to building a dam directly across the stream, and 
it seemed possible that the dam had been originally thus 
built and afterward broken by flood, parts perhaps forced 
down stream, as I had seen, and their ends later connected 
to close the gap. 
Beaver dams are of all lengths, from the trifling ones a 
