228 Dr Forry on the Climate of the United States. 



summer temperature, cannot endure the rigours of winter ; 

 others, slightly sensible to low temperature, require very 

 warm, but not long summers ; while, to others, a continuous 

 rather than a very warm summer seems best adapted. The 

 development of vegetation in the same mean temperature is 

 also retarded or accelerated, according as it is struck by the 

 direct rays of the sun, or receives the diffuse light of a foggy 

 atmosphere. On these causes depend, in a great degree, 

 those contrasts of vegetable life observed in islands, in the 

 interior of continents, in plains, and on the summits of moun- 

 tains. As the region of the great lakes does not exhibit a 

 greater contrast in the opposite seasons than that of Phila- 

 delphia, it follows that plants which, from not being adapted 

 to extremes of temperature, cannot endure the severe winter 

 of Albany, will flourish in the more equalized climate of the 

 same latitude on the ocean or the great lakes. 



Thus, as Volney and JeflFerson saw that the vegetation of 

 Philadelphia is found in the modified climate of our northern 

 lakes, while similar plants will not flourish on the same 

 parallels in the interior of New Yoz*k, Vermont, and New 

 Hampshire, the theory in regard to the diff'erence of tem- 

 perature, east and west of the Alleghanies, was naturally 

 suggested. If, however, these philosophers had chanced to 

 observe the vegetation, by way of comparison, along the coast 

 of Rhode Island or Connecticut, and on the same parallel in 

 Illinois, or farther westward, instead of comparing the region 

 of the lakes and Albany, the world would, of course, have 

 been edified with the opposite theory, — viz., that the climate 

 east of the Alleghanies is milder by 3^ of latitude than that 

 west. While at Fort Trumbull, Connecticut, the mean win- 

 ter temperature is 39" 33', at Council Blufts it is as low as 

 24° 47'. Hence plants sensible to a low temperature, which 

 flourish in the climate of the former, will perish in the latter ; 

 for while the mean temperature of the coldest month at Fort 

 Trumbull is only U° 50', atCoimcil Blufl's it is 22° 61'. This 

 is also demonstrated by the average annual minimum tem- 

 perature, that of the former being 9°, and that of the latter 

 16° ; and equally so by the minimum temperature of the 

 winter months, that of December, January, and February 



