122 



NATURALIST'S GUIDE TO THE AMERICAS 



account by McConnell, who examined it 

 in the summer of 1889: 



The country between the Peace and 

 Athabasca rivers north of Lesser Slave 

 Lake, comprising an area of about 

 44,000 sq. mi., . . . may be de- 

 scribed as a gently undulating wooded 

 plain, diversified with numerous shallow 

 lakes, muskegs and marshes. Small 

 prairie patches, manifestly due to forest 

 fires, occur north of the west end of 

 Lesser Slave Lake, at several points 

 along the Loon and Wabiscaw rivers, 

 . . . but their total area is relatively 

 insignificant. 



The rolling plains between Peace 

 River and the Athabasca are relieved 

 by several high ridges or plateaus, all 

 of which owe their origin to a differential 

 denudation of the soft rocks on which 

 the plains are based. Of these Marten 

 Mountain is situated northeast of Lesser 

 Slave Lake, above which it rises to the 

 height of about 1000 ft. The Buffalo 

 Head Hills commence abruptly about 

 60 mi. above the mouth of the Loon 

 River, with an elevation of about 2500 

 ft. above the Sea, and running in a 

 south-southwesterly direction die away 

 opposite the mouth of Battle River, 

 while Birch Mountain extends for nearly 

 90 mi. along the lower part of the 

 Athabasca, from which it is separated 

 by a plain 16 to 20 mi. wide. Among 

 the smaller elevations are Trout Moun- 

 tain, which is situated north of the 

 Wabiscaw River, and the Thickwood 

 Hills, which lie south of Birch Moun- 

 tain. The uplands of the district, like 

 the lowlands, are all wooded, and are 

 dotted everywhere with lakes and 

 marshes. (Ann. Rept. Geol. Surv. 

 Canada, V, pp. 6D, 7D, 1893.) 



Climatology: The climate of the 

 Athabaska Valley in common with most 

 of the country included in the Mackenzie 

 basin, is characterized by a wide range 

 of temperature. In winter the mercury 

 frequently reaches —40°, while summer 

 temperatures of between 80° and 90° are 

 not infrequent. Its western portion is 

 subject to Chinook winds, which periodi- 

 cally temper the climate. 



Of vital interest to the traveler, who 

 must depend so largely on water trans- 

 portation, are data on the freezing and 

 breaking up of the rivers. In all 

 northern rivers navigation is inter- 

 rupted, before the actual closing of the 

 stream, bj^ drift ice. This is mainly ice 



which has formed in the eddies and 

 which, by a slight rise of water, the 

 usual result of its formation, or from the 

 accumulation of snow upon it, becomes 

 detached and descends the current, con- 

 tinually adding to its own volume. This 

 continues until the increasing cold causes 

 the mass to jam and become solidly 

 cemented. After the breaking up of 

 the rivers in spring the ice, of course, 

 continues to run for a longer or shorter 

 period. 



The following table shows the dates of 

 the opening and closing of the Athabaska 

 at Fort McMurray during a series of 

 years: 



Table showing condition of Athabaska at 

 Fort McMurray 



B. Athabaska Lake Region. Atha- 

 baska' Lake is long and narrow and lies 

 in a general easterly and westerly direc- 

 tion. Its greatest length is about 195 

 mi.; greatest width, 35 mi.; and area, 

 approximately 2850 sq. mi. Its eleva- 

 tion above the sea is about 690 ft. 



The principal tributary of Athabaska 

 Lake is the river of the same name, just 

 described. Its capacity for deposition 

 is so great that, assisted by the Peace, 

 it has filled up a large portion of what 

 was originally the western part of 

 Athabaska Lake, and has isolated several 

 good-sized sheets of water, the largest of 

 which, Lake Claire, is some 35 mi. in 

 length. 



The north shore of Athabaska Lake is 

 mainly rocky and sparsely wooded, and 

 is broken by the mouths of a number of 

 insignificant streams, which help to 

 drain the unexplored country to the 



