BEAVER CANALS, MEADOWS, AND TRAILS. 205 



lines on which they move their cuttings into the 

 ponds. They are narrow, Avell-beaten paths for a 

 short distance from the ponds, but soon lose their dis- 

 tinctness and disappear altogether. They are chiefly 

 interesting as indications of their numbers, and of 

 the long periods of time each dam has been main- 

 tained, and each pond inhabited. 



On the Upper Missouri we meet with another form 

 of trail, which is called a "beaver slide." It is de- 

 signed to maintain, as well as afford, a ready connec- 

 tion between the river and its banks. On both sides 

 of this river, for miles together, the banks are vertical, 

 and rise, at ordinary stages of the water, from three 

 to eight feet above its surface. It would, consequently, 

 be impossible for the beavers to get out of the river 

 upon the land except by excavating a passage-way 

 through the bank, from the river to the surface, or by 

 the construction of the inclined or graded way, known 

 as a " beaver slide." The latter expedient was adopted 

 and made the ordinary run-way to and from the river, 

 and the bottom lands upon its border. They are sim- 

 ple excavations in the bank, in the form of a narrow 

 passage-way, inclined at an angle varying from 45° to 

 60°, so as to form a gradual descent from a point a 

 few feet back of the edge of the bank to the level of 

 the river. Several of them are often seen in the 

 bank, within ten feet of each other, as shown in the 

 Plate. (Plate XXIII.) ^ They are first seen near the 



^ In the foreground in this engraving is shown the "Bull Boat" 

 of the Upper Missouri, used by the Mandans, Minnitares, Crows, 

 and Blackfeet, for crossing the river. It is made of a single raw 

 hide of a buffalo, unhaired and stretched over a dome-shaped 

 frame of splints. It is safe, convenient, and portable ; and it will 

 carry two persons. 



