50 THE BEAVER 
Pass, Colorado. To prevent the animals from destroying 
the few trees about the lake the townspeople carried green 
brush to them, which supplied food and also material for a 
lodge which they built beside an island in the lake. In 
1926 they were still living there and had increased in number 
- to four. 
Such occurrences as the washing away of dams by floods 
are common happenings on our western streams, if not 
elsewhere. In the mountains these floods are usually due 
to melting snow in spring, which often raises a stream several 
feet above its ordinary level, and at lower altitudes cloud 
bursts in summer may send down large volumes of water at 
one time which tear out almost any obstructions which may 
be in their path. The floods in Colorado, in June, 1921, 
carried out every dam on a long stretch of one stream with 
which I am familiar, and changed the channel in many 
places. What the beavers did during the high water I do 
not know, but after the flood receded they evidently re- 
turned and built new dams, and there are still flourishing 
colonies on the stream. 
Mills, speaking of the ‘‘Moraine Colony” at a time when 
it was deserted, said that the stream had cut deeply through 
the old main dam, and this showed that it had been built on 
top of an older and filled-up pond; this second dam was on 
top of a still older one. In the sediment of the oldest pond 
were found a spear head, charred logs, and a buffalo skull. 
Dugmore says: “Agassiz, speaking of the age of beaver 
work, mentions the building of a milldam which required 
some excavating. “This soil was found to be peat bog. A 
trench was dug into the peat 12 feet wide, by 1200 feet long, 
and 9 feet deep; all the way along this trench old stumps of 
trees were found at various depths, some still bearing marks 
of having been gnawed by beaver teeth’.”’ By calculating 
the growth of the bog as about a foot a century there is 
