480 APPENDIX. 



terminates only thirty or forty miles to the southward of 

 it ; and we thus possess the means of ascertaining how 

 far to the north a summer temperature of 52° extends. 

 But, in fixing this limit, some allowance must be made 

 for altitude, and the nature of the soil. Thus, on the 

 low alluvial delta of the Mackenzie, the spruce fir 

 reaches the latitude of 68° ; and the banks of that river 

 generally are better wooded than the more elevated rocky 

 tracts which lie to the eastward. 



The permanence of the frosts when once they set in 

 is a feature of the climate of the fur countries which 

 requires to be noticed here, as it influences the dis- 

 tribution of graminivorous and herbivorous animals * 

 by modifying their supply of food. The carices 

 and grasses have scarcely matured their seeds before 

 they are frozen up for the season while their leaves 

 are still full of sap ; thus they continue to afford good 

 pasturage until the spring, and they drop their seeds 

 only when the melting snow has prepared the ground 

 for their reception. The sparrows and buntings profit 

 by this vernal harvest. In like manner the Vaccineae, 

 Arbuti, and several other berry-bearing shrubs, retain 

 their fruits until the same period, when they yield food 

 to the bears, just awoke from their winter sleep, and 

 to large flocks of geese winging their way to their 

 breeding places. 



The northern boundary of the woods is the limit of 

 the range of the black bear, the American fox, the pine- 

 martin, the fisher, the lynx, the beaver, several mar- 

 mots, the American hare, the moose deer, the Canada 

 partridge, the woodpeckers, &c. The " barren 



* Beasts and birds of prey depending on these tribes for subsist- 

 ence are also thus influenced in their distribution by the powers 

 of vegetation. 



