THE DAM ao 
I saw two or three small dams in a group on Tower Creek, 
Yellowstone Park, where half-decayed pine logs formed part 
of the dam. I think it probable that the beavers intention- 
ally made use of these fallen logs as part of their dams, 
which belonged to a series of storage ponds. It certainly 
seems rather unlikely that several logs should have fallen 
across so many dams in the same group after the building 
of the dams. A. H. Howell, in the Biological Survey of 
Alabama, states that beaver built small dams across Catoma 
Creek in that state, generally utilizing “trunks of fallen 
trees (not of their own cutting) for a foundation, filling in 
the space between the logs with sticks, cane stalks, leaves 
and mud.” 
In Gunnison County, Colorado, I found a dam twenty 
feet long and eight feet wide on top, built across a slough 
having little or no current. This appeared to be constructed: 
largely of mud, though a certain percentage of sticks was 
also visible. It was evidently quite old at the time of 
my examination, but a little work had recently been done 
on it. 
In 1899 a surveyor named John Harrold was running sec- 
tion lines in the Little Missouri Badlands, immediately west 
of the Killdeer Mountains, North Dakota, and discovered 
three or four beaver dams built of coal. The face of one of 
these was six feet high. The coal came from a nearby bluff. 
Taylor, who is the authority for the above, also mentions 
dams on the Upper White Earth River, North Dakota, built 
entirely of stones, some of which would weigh as much as 
fifty pounds.! Mills speaks of a dam in the Sawtooth Moun- 
tains, Idaho, constructed of logs from a snowslide. I have 
myself seen a few sticks from a snowslide utilized in a dam. 
Morgan speaks of three dams discovered in Montana 
which were in a petrified state. ‘They were not in that 
1 Taylor, Beavers, Their Ways. 
