1908.] 



PHYSICAL GEOGRAPHY PEACE EIVER VALLEY. 



25 



Slave Lake. In this stretch it has an average width of about half a 

 mile, and its banks are high at first, but gradually diminish. The 

 country bordering it is level and mainly well wooded, but to the west 

 are extensive tracts of prairie, especially in the region of Salt River, 

 its principal tributary, Avhich enters the Slave from the west 10 miles 

 below the rapids. Slave River enters Great Slave Lake through an 

 extensive delta, in forming which it has silted up an extensive arm of 

 the lake. 



The Peace River Valley, as here considered, exhibits the greatest 

 diversity of climatic conditions at the same season of aii}^ of the re- 

 gions now under discussion, excepting possibly the Liard River Valley. 

 Its extreme upper portion, lying at a comparatively low altitude and 

 hear the Pacific, has a relatively mild winter climate, while its lower 

 l^art at the same season is surrounded by almost Arctic conditions. 

 Its middle part, just east of the mountains, seems to be characterized 

 by violent extremes of temperature, judging hj the figures for Dun- 

 vegan, the only post for which I have been able to obtain a complete 

 record. For the extreme upper and lower portions, exact data being- 

 wanting, data for near-by localities may be substituted. Thus the 

 temperatures for Stuart Lake, a locality lying close to and at about 

 the same altitude as the extreme headwaters of the Parsnip, probably 

 represent approximately the conditions in the valley of the upper 

 Peace. In the same way the table for Fort Chipewyan, elsewhere 

 given (see p. 23) , may be taken as an index of the climate of the lower 

 Peace River proper, and that for Hay River, Great Slave Lake (see 

 p. 28), as fairly representing the lower Slave. 



Summaries of temperatures taken at Stuart Lake, British GolumMa, cluriug 



the year 1900. 









Extremes. 





Month. 



Mean daily 



Mean daily 







Monthly 





maximum. 



minimum. 



Maximum. 



Minimum. 



mean. 



January _ __ _ __ 



18.6 



3.4 



44.0 



-29.7 



11.0 



February _ 



14.1 



- 3.0 



33.9 



-38.6 



5.5 



March_- 



23.1 



2.3 



45.0 



-30.2 



12.7 



April 



42.9 



21.5 



64.0 



14.2 



32.2 



May 



52.2 



27.5 



65.0 



20.2 



39.9 



June 



59.4 



33.2 



77.5 



22.2 



46.3 



July 



64.4 



38.3 



81.0 



31.2 



51.3 



August 



59.5 



35.3 



70.0 



18.2 



47.4 



September 



55.0 



28.9 



68.0 



19.2 



41.9 



October _ _ _ 



39.7 



22.4 



54.0 



2.1 



31.0 



November 



27.7 



11.3 



43.0 



-27.4 



19.5 



December ___ _ 



30.0 



15.8 



43.0 



-15.6 



22.9 



Year- 







81.0 



-38.6 



30.8 









The ' Chinook ' winds exert a powerful, though irregular, influence 

 on the climate of the middle Peace River Valley and, together with 

 a favorable soil, allow a considerable amount of agricultural de- 

 velopment. 



