i68 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. 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. 



