SOME INTERESTING BEAVER DAMS IN COLORADO 435 



had built a dam and formed a small pond. This ditch was dug 

 in 1902 which thus fixes the date of that dam. 



The 2 ponds shown at the northwest corner of the map (PL 

 xxvi) are rather old. I saw them in 1900, but when the survey 

 was made there was fresh beaver sign all about. The 3 trails 

 between the lower pond and river were within a space of 80 feet 

 and showed signs of regular use. 



About three-quarters of a mile above these last workings are 

 2 series of 3 dams each, and all along the stream are many 

 signs of the animals in the way of brush cuttings and landing 

 places. The lower of these 2 series had i dam extending 

 part way across the stream, and 50 feet above it are the other 

 2, nearly opposite each other, i on each side of the stream, but 

 not coming out far enough to meet. There is a bend in the 

 river here and it is quite wide. One of these 2 dams had many 

 sticks in the lower side pointing down stream, while the other 

 had many stones banked against its upstream side. 



The other series of 3 is a few hundred feet above (PL xxxii, fig. 

 i). The upper dam of the set is on the easterly side of the river 

 and extends about half way across, 25 feet below and on the 

 opposite side is the middle dam, also extending half way across 

 the stream, which is here 40 or 50 feet wide ; 65 feet below that, 

 and on the same side of the river, is the third dam, like the 

 other 2 reaching half way across. Twenty-five feet below the 

 third dam and on that same side is a small one running out into 

 the stream about 8 feet. The upper dam backed up quite a lot 

 of water but it is not any great depth as the river has too much 

 fall. The other 2 dams did not, I think, deepen the water very 

 much, but created still water more to the beavers' tastes. All 

 the dams in this part of the river contain more or less spruce 

 sticks which had been brought to the river from the steep hill- 

 sides on the west by snow slides during the winters. 



Another interesting set of workings, though long since aban- 

 doned, is in a slough on the east side of the river valley a short 

 distance outside the map limits. Here the dam has been cut 

 through by a ranchman to drain the pond so that everything is 

 exposed. The dam was 105 feet long, the outlet, which was 

 the slough that furnished the water, was 42 feet from the east 



