78 Dr Forry on the Climate of the United States. 



the two seasons, so great is the modifying influence of the 

 ocean, is no more than 19°'62, while at Uleo, in the interior 

 of Lapland, the difference between the mean temperature of 

 summer and winter is 45°*90. 



In these comparisons of the Northern division, no particu- 

 lar reference has yet been made to Fort Vancouver, in Ore- 

 gon Territory. This region bears the same climatic rela- 

 tion to our coast and to that of Eastern Asia, as the western 

 coast of Eui-ope does. The mean annual temperature is 

 about 10° higher than that of the posts on the same parallel 

 on our own coast. So mild and uniform are the seasons at 

 Fort Vancouver, that the diiference between the mean tem- 

 perature of winter and summer is only 23°-67, a mean which 

 is less than that of Italy or southern France, and only about 

 two-fifths of that of Fort Snelling, Iowa, notwithstanding the 

 latter is nearly 1" farther south. This contrast is well ex- 

 hibited in Plate I. ; for while the mean temperature of spring, 

 summer and autumn, at Fort Vancouver, is about the same 

 as at Fort Wolcott, Rhode Island, the winter line comes 

 nearly as far south as Fort Gibson, Arkansas. But even this 

 comparison, at first view, falls short of the reality ; for, as 

 regards the difference between the mean temperature of 

 winter and summer, the contrast is less at Fort Vancouver 

 than at Cantonment Clinch near Pensacola, or Petite Coquille 

 near New Orleans. These results, however extraordinary 

 they may appear, find, as will be seen, an explanation in 

 physical causes. 



The next point demanding attention is the difference be- 

 tween the mean temperature of winter and spring, which is 

 much the greater in the excessive or rigorous climates. 

 Taking places in the same latitude and in opposite systems of 

 climate, it is found at Fort Brady to be 18°-42, while at Han- 

 cock Barracks it is 24°-49 ; at Fort Sullivan it is IT-ld, 

 while at Forts Snelling and Howard, it is respectively SO^-S 

 and 24°-10, the latter being partially modified by Green Bay ; 

 at Forts Preble, Niagara, and Constitution, and the city of 

 Salem, the ratios are 18°-42, 16°-77, 16°-83, and 17'-89, and at 

 Fort Crawford, on the other hand, it is 25"-83 ; and, lastly, at 

 Forts Wolcott and Trumbull, it is 14°-71 and n°-67 ; while 



