130 SIXTH REPORT — 1836. 



terior at Fort Enterprise and Fort Franklin, in 64i° and 65°, 

 there are two such months. In latitude 45" near the middle of 

 the continent there are five, in latitude 35° there are nine, and 

 towards the southern extremity of Louisiana, in 29^° N. lat., 

 there are eleven ; while within the tropics the trees are ever- 

 green. 



The gradual ascent of the isothseral lines as they recede from 

 Hudson's Bay is sho^vn by the direction of the northern termi- 

 nation of the woods. On the coast near Churchill trees cease 

 about the 60th parallel j but at the distance of sixty miles from 

 the sea their boundary line rises rapidly, and then takes nearly 

 a straight W.N.W. course, until it reaches Great Bear Lake, 

 in latitude 65°: still further west on the banks of the Mackenzie 

 the woods run to 68° N. lat. We do not know the course of the 

 line of termination of the woods in the interior of Russian Ame- 

 rica. In the elevated lands of New Caledonia the snow is said 

 to be very deep in winter, and to cause a great scarcity of the 

 larger ruminating animals ; but near the mouth of the Columbia 

 there are almost constant rains during that season, with little 

 frost or snow. There are some peculiarities in the climate of 

 Lower California and the adjoining parts of Mexico, which are 

 mentioned in the subjoined note'"^. 



In the high latitudes of North America, at some distance 

 from the coast, the intense colds of winter have a very consi- 

 derable, though indirect influence on the summer vegetation, 

 and consequently on the capabilities of the country for main- 

 taining animal life: for independent of the accumulation of 



* In a paper by Dr. Coulter, published in the 5th vol. of the Transactions of 

 the Geographical Society, the following remarks on the climate of Mexico and 

 California occur; — "The mercuiy in a thermometer shaded from the sun, but 

 within the influence of radiation from an arid plain, frequently stood at 140° F., 

 but this great heat was owing to temporary and local causes. The surface of 

 the country, composed of bare mountains or arid plains completely destitute of 

 water, does not mitigate the cold winds blowing from the Rocky Mountains 

 lying to the north and novth-east ; hence when they blow for any length of 

 time it freezes even to the south of Pitis, in latitude 29° N., and in the winter 

 of 1829-30 it froze at that place every night for nearly two months. On the 

 table land of Mexico similar cases of cold occur more frequently, as may be 

 easily conceived from their greater elevation and the same general scarcity of 

 water. At Veta Grande, Zatatecas, during the month of December, 1825, it 

 frequently froze hard. The condition of the counti-ies on the confines of Sonora 

 and California is peculiar, as lying between the summer and winter rains. The 

 whole rain of Mexico may be said to fall in the summer months, but in Upper 

 California it rains only in the winter. The summer rains reach the lower part 

 of Sonora, where they are scanty and irregular, and from Pitis northwards 

 across the sands it rarely rains at all ; as is also the case in the northern por- 

 tions of Lower California, where the summer rains scarcely prevail to the 

 northward of Loretto, the capital." {Lib. cit., p. 70.) 



