170 THE AMERICAN BEAVER. 



tions. To guard against this danger, the dam, also, 

 must be sufficiently stable through the winter to 

 maintain the water at a constant level; and this 

 level, again, must be so adjusted with reference to the 

 floor of the lodge as to enable them, at all times, to 

 take in their cuttings from without, as they are 

 needed for food. When they leave their normal mode 

 of life in the banks of the rivers, and undertake to 

 live in dependence upon artificial ponds of their own 

 formation, they are compelled to forecast the conse- 

 quences of their acts at the peril of their lives. 



Before entering upon the subject of tree cuttings, it 

 may be proper to make a slight reference to the char- 

 acter of the forests in the principal beaver districts re- 

 ferred to in these pages. On the Upper Missouri and 

 its tributaries, cotton-wood is the prevailing tree, and 

 willow the principal bush. In this region, therefore, as 

 their favorite subsistence is both abundant and conve- 

 nient of access, beavers have been found in the greatest 

 numbers. Upon the Siskatchewun and its affluents, 

 the forest growth is much the same, with a limited 

 proportion of evergreen trees. Around Hudson's Bay 

 and the shores of Lake Superior, the prevailing trees 

 are the tamarack, the spruce, the hemlock, and the 

 pine, but they are interspersed with the birch, the pop- 

 lar, the maple, and other deciduous trees, and also 

 with patches of willow upon the borders of the 

 streams; which together furnish such an abundance 

 of subsistence as to render them but little inferior 

 to the first for beaver occupation. The only differ- 

 ence against the latter is the necessity for transport- 

 ing their cuttings over longer distances. In Cali- 

 fornia, Oregon, Washington, and British Columbia, 



