168 Frertp Museum or Natural History — Zoé.oey, Vot. XI. 
pieces are pushed and rolled into these canals often by several Beavers 
working together and using their shoulders and bodies as well as their 
teeth and paws in their efforts. Some of the canals are of extraordinary 
length. Morgan found several more than 500 feet long, one of which 
was situated on the Carp River, Michigan,* and which he describes 
as follows: 
“There is an extensive canal on Carp River a short distance below 
the bend . . . It runs through low, swampy ground, which is 
covered for one-quarter of its length with a thicket of alder so dense that 
it was difficult to follow the channel for the purpose of measurement. 
The river, which at this point is a hundred feet wide, more or less, is 
bordered with alder and cranberry bushes, and with a forest of tama- 
racks. Back of these, some six hundred feet, is the first rising ground 
covered with deciduous trees, to reach which the canal was constructed. 
At the distance of one hundred and eleven feet from its commencement 
in the river there was a rise in the surface level of about a foot, which 
made necessary either a dam or an additional foot of excavation to 
furnish sufficient depth of water. A dam twenty-five feet long across 
the canal and the grounds adjacent, was the expedient adopted. The 
second level of the canal, thus raised a foot above the first, continued 
one hundred and seventy-eight feet, where a second rise occurred of 
about the same amount, and where a second dam was constructed thirty 
feet long. As the ground on both sides of the canal was swampy, with 
water in pools here and there, it was only necessary to excavate a channel 
of requisite depth to obtain a sufficient supply of water by filtration 
from the adjoining lands. Up to the first dam the canal was filled 
from the river, and consequently varied in depth with the rise and fall 
of the stream; but above this, where it depended upon the dam and 
the source of supply before named, it was uniformly about 18 inches 
deep. From the second dam the canal continued at a foot higher 
level for the distance of two hundred and ninety feet, where it ter- 
minated at the base of the hard wood lands at a distance of five hundred 
and seventy-nine feet from the river. Its average width was about 
four feet, and it had an unobstructed channel of about eighteen inches 
deep from one end to the other, with the exception of the dams. The 
runways of the beavers over these dams were very conspicuous. They 
were shown, as in the other cases, by a depression in the center formed 
by travelling over them in going up and down the canal. At the 
mouth of the canal the river was not deep enough for a beaver to swim 
below its surface out into the stream. To obviate the difficulty, a 
_ *Southwest of Teal Lake, about 15 miles west of Marquette and less than 50 
miles from the Wisconsin line. 
