1 908. 1 



LIFE ZONES — CANADIAN. 



53 



The following table shows the mean temperature of the two 

 warmest months (usually June and July), and the mean temperature 

 for the year at various stations in the Athabaska-Mackenzie region : 



Table showing mean temperature of two warmest months of year <nirf for entire 

 year at various stations. 



"Approximate. 



''.Tune only. 



In the case of a few stations it would have been possible to obtain 

 the means of two or more years, but it is believed that the figures 

 for 1900, being more directly comparable, are, on the whole, more 

 satisfactory and represent fairly'well the normal conditions. It is 

 manifest that these data are much too scanty to afford assistance in 

 platting life zones or in formulating general laws, but a few signifi- 

 cant points may be noted. If these figures are platted on a map, it 

 will be seen that the mean temperature of the two warmest months 

 is very uniform throughout the Canadian zone, the greater amount 

 of sunlight compensating for the higher latitude in the case of the 

 more northern localities, while the mean temperature for the year 

 lowers rapidly toward the northward. Omitting the means for 

 Athabaska Landing, which seem to be lower than the position of the 

 place would warrant, the extremes for the two warmest months for 

 the places within the Canadian zone are 57.4 and 50.4, and the 

 average 5s. 4° F. Merriam considers that the mean temperature of the 

 six warmest weeks of summer has an important bearing on the dis- 

 tribution of species. Exact data for this period can be obtained for 

 SO few localities in the north that the figures would be of little value, 

 but it is believed that the mean temperature of the two warmest 

 months would be found to be only a degree or two lower. Corre- 

 sponding temperature data for more easterly points in the Canadian 

 /one vary only 2° or 3°, and lead to the conclusion that in that region 

 a mean of approximately C)0° F. for the six warmest weeks of summer 

 characterizes the Canadian zone. 



Data for the Iludsonian and Arctic zones are less full, but so far 

 as they go indicate that the limiting temperatures for the southern 

 boundaries of the Iludsonian and Arctic zones are approximately 

 57° F. and 50° F., as stated by Merriam. 



"Nat. Geog. Magazine, VI, ]». 236, 1894. 



