CANALS, TRAILS, AND LANDING PLACES 83 
ditch at the pond level so that the water will fill it, but quite 
another thing to make one at a level above this and build a 
dam to retain the water derived from some other source, 
and thus avoid digging the pond level portion to an imprac- 
ticable depth. 
Speaking of a certain canal Mills says that the mud dug 
out in making it was piled evenly along the lower side, and 
looked more like the work of a careful man with a shovel 
than of beavers without tools. He also mentions a canal 
begun at the Moraine colony and then abandoned because 
the beavers discovered they could not make it carry the 
water where they wished. He describes a series of canals 
dug in the bed of Lily Lake, Estes Park, at a time when the 
water had fallen so low that there was not sufficient left for 
the use of the beavers. It finally receded so much that the 
only water left was in the ditches, which must have been the 
work of years. For a detailed description I refer my readers 
to his book. It must suffice to say here that these canals 
varied in length from quite short ones up to one 750 feet 
long. Mills states that he has known of beavers extending 
canals in the bottom of a pond and making submarine 
tunnels when the pond was ice-covered. 
In another book,! describing the struggle of a colony for 
existence during winter, Mills states that a ditch two feet 
wide and nearly as deep was dug from the house in the center 
of the pond to the upper portion, which had been swampy 
before being flooded, and where they were able to secure 
enough roots of various sorts to ward off starvation. This 
was, of course, after ice had covered the pond. 
Mr. Mills called my attention to a canal on the Roaring 
Fork which differed from the usual type in having a very 
steep grade. The beavers were harvesting aspens some 
1 Famine in Beaver Land, in Watched by Wild Animals. 
