74 Dr Forry on the Climate of the United States. 



self to mere results, referring the reader who may be more 

 curious on this subject to the author's work, " The Climate 

 of the United States, and its Endemic Influences," wliich 

 contains a series of extensive tabular abstracts of instru- 

 mental observations. These residts are obtained from ob- 

 servations made at the various military posts between 24° 33' 

 and 46° 39' of north latitude, embracing a space of 22° 6', 

 and an extent of longitude stretching from the Atlantic to 

 the Pacific. The thermometrical observations were made 

 thrice daily ; and as the mean of each month is calculated 

 from 90, and of each year from 1095 observations, the nu- 

 merical ratios, it is believed, will give an approximation to 

 the truth as near as can be realized by ordinary observation, 

 and a mean suf&ciently correct for every contemplated pur- 

 pose. The results, at the majority of the posts, are based 

 on from five to ten thousand observations. 



1. The Northern Division. — As this region presents the 

 greatest diversity of physical character, so it exhibits the 

 most marked variety of climate. East of the chain of great 

 lakes there are several mountain ranges, which, with the ex- 

 ception of a few summits, seldom attain a height of more 

 than 2500 feet above the level of the sea ; and of this eleva- 

 tion, perhaps one-half is formed by the table-lands upon 

 which the ridges rest. Above the falls of Niagara, the 

 region of the lakes is elevated 600 to 700 feet above the 

 ocean, but there are scarcely any ridges that deserve the 

 name of mountains. This immense tract is, with the excep- 

 tion of the eastern states, nearly altogether in a state of 

 nature, being still covered with its dense primeval forests. 

 But the most striking characteristic in the physical geo- 

 graphy of this division, is that produced by its vast lakes or 

 inland seas. "We here behold a chain of lakes presenting a 

 superficial area of 94,000 square miles, with a mean depth 

 of 1000 feet in the principal lakes, the details of which have 

 just been given. 



In accordance with the diversity in the physical geography, 

 we find that, on the sea-coast of New England, the influence 

 of the ocean modifies the range of the thei'mometer ; thus 

 equalizing the temperature of the seasons. Advancing into 



