Dr Forry on the Climate of the United States. 79 



at Council Bluffs, Fort Armstrong, and West Point, it is re- 

 spectively 27°-47, 23°-99 and 18°-82. Fort Columbus, as in 

 the preceding comparisons, stands as an exception, its ratio, 

 notwithstanding it is lower than any one in the opposite 

 class, being the highest in its own, with the exception of two 

 posts. The peculiarity in the increase of the temperature of 

 spring, as manifested in the vegetable kingdom, constitutes 

 a feature w^hich strongly characterizes excessive climates ; 

 for, as Baron Humboldt remarks, " a summer of uniform 

 heat excites less the force of vegetation, than a great heat 

 preceded by a cold season." Accordingly, we find that in 

 these excessive climates (unlike the uniform ones on the ocean 

 and lakes, in which the air is moist, and the changes of the 

 seasons slow and uncertain), summer succeeds winter so ra- 

 pidly, that there is scarcely any spring, and vernal vegetation 

 is developed with remarkable suddenness. At Fort Vancou- 

 ver, the difference between the mean temperature of winter 

 and spring is only 6°'67, which is about one-third of the dif- 

 ference observed at the posts in our modified climates on the 

 same parallel, and little more than one-fifth of the difference 

 exhibited in the excessive climate at Fort Snelling, 



Another feature which characterizes these two systems of 

 climate remains to be considered, viz. the mean annual range 

 of the thermometer. Comparing the posts on the same pa- 

 rallel, the following relations are found : — At Fort Brady, 

 on the one hand, the range is 110°, and at Hancock Bar- 

 racks, on the other, it is 118° ; at Fort Sulivan it is 104°, 

 while at Forts Snelling and Howard, it is 119° and 123° ; at 

 Forts Preble, Niagara and Constitution, it is respectively 

 99', 92°, and 97°, while at Fort Crawford, on the same pa- 

 rallel, it is 120° ; and lastly, at Forts Wolcott and Trum- 

 bull, it is 83° and 78°, while at Council Blufi's, Fort Arm- 

 strong, and West Point, it is 120°, 106°, and 91°. Fort Co- 

 lumbus, as before, presents an exception. In further eluci- 

 dation of the law regulating the extremes of temperature, the 

 four following posts, which are all nearly on the same paral- 

 lel of 41° 30', the first two being on the ocean, and the last 

 two far in the interior, remote from large bodies of water, 

 may be adduced as striking examples : 



