18 NORTH AMERICAN FAUNA. [no. 27. 



50 miles and then resumes its northerly course. In the course of 

 the next 150 miles it receives in succession La Biche River from the 

 east (fig. 1); Quito or Calling River from the west; Big Mouth 

 Brook from the east; Pelican River from the west; and House River 

 from the east. Just below the mouth of the last river the Athabaska 

 strikes a range of low hills, and in forcing a passage through them 

 is deflected eastward, and for a distance of about 75 miles contains 

 many rapids, falling in this distance some 400 feet. At the lower end 

 of this stretch it receives the waters of Clearwater River, its principal 

 tributary below Lesser Slave River. The Clearwater rises on the 

 height of land between the Churchill and the Athabaska, and, pur- 

 suing a nearly straight easterly course for some 150 miles, mingles its 

 limpid Avaters with the sediment-laden ilood of the latter stream. In 



Tig. 2. — A brule or fire-swept forest, Athabaska River, below Grand Rapid. 



the lower part of its course the Clearwater occupies a deep valley 

 and is very rapid. Thirty or forty miles above its mouth it is joined 

 by the Pembina, a stream of about equal volume. 



Below the mouth of the Clearwater the Athabaska pursues a nearly 

 direct course northward, receiving Red, Moose, and Tar rivers from 

 the west, and enters Athabaska Lake through a number of channels 

 inclosing alluvial islands. Besides the rivers mentioned, scores of 

 lesser streams enter the Athabaska throughout its course. 



The country drained by the Athabaska is mainly a rolling plain, 

 and with the exception of a few areas of semiprairie land is well 

 wooded with a forest composed mainly of spruce, fir. pine, tamarack, 

 poplar, birch, and willow. A large part of its surface is occupied by 

 mossy swamps, called muskegs (PI. V, fig. 2), and hundreds of ponds 



