30 THE BEAVER 
laid across the stream (Fig.9). I have seen several instances 
where this appeared to be quite evident. The sticks here 
were usually rather small. It also seems possible that some 
movement may occur in the inevitable settling of a dam 
which shifts some of the sticks, causing them to take this trans- 
verse position. When a dam is completed sticks and brush 
are often seen lying lengthwise on the top, and the peeled 
sticks carried there after the bark has been eaten from them 
lie in various positions, criss-cross, as one writer expresses it. 
Many sticks of this sort drift to the dam and lodge there. 
Sticks carried to the lower face of a dam after its completion 
seem to be dropped there in almost any manner. I have 
seen one dam in Colorado which had long pine poles placed 
along its face so that their ends projected quite high above 
the dam (Fig. 10). 
One dam which I found in Colorado, built upon a bench a 
few feet above the stream, had willow brush laid horizon- 
tally between clumps of willows which were along the course 
of the dam. As the water in the pond came from springs 
there was practically no current to resist, and this somewhat 
weak form of construction was of no detriment to the dam. 
Dams consisting wholly of mud or sods are sometimes 
built. The one or two which I have seen were in swampy 
ground where there was no current, and were made by 
excavating the material from above the dam and piling it up 
along the desired location. In one case in the Yellowstone 
the whole pond was thus excavated in building the dam. 
This pond was apparently constructed for water storage. 
It is sometimes stated that trees are felled across a stream 
in beginning a dam, but it is exceedingly doubtful if this is 
ever the case. Morgan mentions one instance where a 
large fallen pine formed part of a dam, but he was in doubt 
as to whether the tree had fallen before the beginning of the 
dam, and thus suggested the site to the beavers, or had fallen 
on the dam after it was built, 
