222 Dr. Forry on the Climate of the United States, fyc. 



* 



64°*40, is true only of the same system of climate. As the annual 

 quantity of heat which any point of the globe receives, varies 

 very little during a long series of years, the variable product of 

 our harvests depends less on changes in the mean annual tempe- 

 rature, than in its distribution throughout the year. Thus cli- 

 mates in regard to vegetable productions, are strongly character- 

 ized by the variations which the temperature of months and sea- 

 sons experience. But this subject is too extensive for present 

 investigation. It has been already observed that the parallels, 

 which, in western Europe, yield the olive and the orange, are 

 with us productive of ice and snow ; but on the Pacific coast of 

 our territory, the requisite temperature, is found at Fort Vancou- 

 ver, which is it) the latitude of Montreal. Here vegetation grows 

 luxuriantly in mid-winter. That vegetables common to the 

 warm climates, as the orange, lemon, citron, fig, olive, and pome- 

 granate, can be successfully cultivated here, is no longer a doubt- 

 ful question ; and the cotton-plant also, is said to flourish well. 

 The British Fur Company at Fort Vancouver, besides cultivating 

 all these plants, have likewise a fine grapery, which yields fruit 

 equal to those in France. 



The influence of the unequal distribution of heat upon vegeta- 

 ble geography is beautifully illustrated in the four systems of 

 climate demonstrated on the same parallels in the Northern divi- 

 sion of the United States ; and if we extend the comparison to 

 the Pacific coast, a fifth system may be enumerated on the same 

 latitude. Taking the coast of New England, the region of the 

 great lakes, and the Pacific coast, the difference between the mean 

 temperature of winter and spring varies from 6°-67 to 18 0, 42; 

 while in the excessive climate of the region west of the lakes, 

 and that intermediate to the lakes and the Atlantic, this differ- 

 ence ranges from 18°-82 to 30°83 ; and accordingly we find, as 

 already explained, that spring and summer, in the latter, are con- 

 founded with each other, and that the sudden excess of heat ren- 

 ders the progress of vegetation almost perceptible. It is necessa- 

 ry, however, to add that the low ratio of 6°67 occurs on the Pa- 

 cific coast, the lowest average in the Northern division of the 

 United States being ll°-67. In the Middle and Southern divi- 

 sions, this vernal increase of temperature gradually diminishes, 

 until finally at Key West it is only 5°-99. But there is another 

 important feature to be observed. Not only is the vernal increase 



