232 Dr. Forry on the Climate of the United States, ^'c. 



sufficiently powerful sun in summer, are affected by our compar- 

 atively moderate frosts in winter ; while upon continents in the 

 same degree of latitude, the same trees arrive at the highest de- 

 gree of perfection." 



As the writer has found the opinions of M. Yolney, as well as 

 those of Jefferson, Williams, and Rush, quoted as oracular in every 

 work professing to treat of our climate, it may not be amiss to ex- 

 amine this subject a little more in detail. This French philoso- 

 pher had the singularly bad fortune of adopting the errors of Dr. 

 Rush and Mr. Jefferson. For example, according to the former, 

 as we recede from the ocean into the interior of Pennsylvania, 

 "the heat in summer is less intense," — a phenomenon contrary to 

 every law of nature, unless reference was had to the Alleghany 

 elevations ; and, in accordance with the latter, the climate be- 

 comes colder as we proceed westward on the same parallel until 

 the summit of the Alleghany is attained, when this law is revers- 

 ed until we reach the Mississippi, lohere it is even warmer than 

 the same latitude on the sea-hoard. This theory, by the way, is 

 ^^y^se^M^gonihetestimony of travellers ; and "their testimony," says 

 Jefferson, "is strengthened by the vegetables and animals which 

 subsist and multiply there naturally, and do not on our sea- 

 board." "As a traveller," adds Volney, "I can confirm and en- 

 large upon the assertion of Mr. Jefferson ;" and in regard to the 

 temperature of the regions lying east and west of the AUeghanies, 

 he concurs in the opinion, "that there is a general and uniform 

 difference equivalent to 3° of latitude in favor of the basin of the 

 Ohio and the Mississippi." This conclusion, which is not de- 

 duced from thermometrical data, rests, it will be observed, upon 

 the phenomena of temperature and of vegetation exhibited in the 

 region of the great lakes. "Even as high up as Niagara," he 

 continues, "it is still so temperate that the Cold does not continue 

 with any severity more than two months, though this is the most 

 elevated point of the great platform — a circumstance totally in- 

 consistent with the law of elevations." He proceeds to say that 

 this climate does not correspond with similar parallels in Vermont 

 and New Hampshire, "but rather with the climate of Philadel- 

 phia, 3° farther south. * * * At Albany, no month of the year is 

 exempt from frost, and neither peaches nor cherries will ripen." 

 The influence of the great lakes in modifying temperature has 

 been already so abundantly demonstrated, that further illustration 



