98 Dr Forry on the Climate of the United States. 



Here, then, although there is not a degree of difference in 

 the mean annual temperature of Fort Vancouver and Coun- 

 cil Bluffs, yet the mean \vinter temperature of the latter is 

 nearly seventeen degrees lo7ver, while the mean summer 

 temperature is nearly eleven degrees higher. But this con- 

 trast is exhibited in a still more marked degree by comparing 

 the difference between the mean temperature of winter and 

 summer, the former being 23''67, while the latter is 51°'35. 



" In tracing five isothermal lines between the parallel of 

 Rome and St Petersburg." continues Humboldt, " the cold- 

 est winter presented by one of these lines is not found again 

 on the preceding line. In this part of the globe, those places 

 Avhose anniial temperature is 54'^-50 have not a v/inter below 

 32^, which is already felt upon the isothermal line of 50." 



In the European climate, two points having the same 

 winter temperatui'e may differ as much as 11° in latitude. 

 Thus in Scotland, in latitude 57^, and isothermal line 45'''50, 

 the winters are more mild than at Milan, in latitude 45 23', 

 and isothermal line 55°-80. Consequently, the lines of equal 

 winter cut isothermal lines which differ 10°. At the isle of 

 Maggeroe, at the northern extremity of Europe, under the 

 parallel of 71°, the winters are 7° milder than at St Peters- 

 burg, latitude 59° 56'. In the United States, embracing the 

 whole region between the Atlantic and the Pacific, as gi'cat 

 a contrast no doubt exists. The mean winter temperature 

 of Fort Vancouver, Oregon Tenntory, latitude 45° 37', is 

 found about 9° farther south, at a point intermediate to 

 Fort Gibson and Jefferson Barracks ; but if the observations, 

 like those in Scotland just referred to, were made on the 

 coast (Fort Vancouver being seventy miles distant from the 

 Pacific), the winter temperature would necessarily be still 

 higlier. As the mean annual temperature of Fort Vancouver 

 is 51°-75, and that of the assumed point between Fort Gib- 

 son and Jeft'erson Barracks is about 61°, it follows that the 

 lines of equal winter cut isothermal lines which differ more 

 than 9° of Fahrenheit. (See Plate II.) 



In Europe a greater deviation from the terrestrial parallels 

 is caused by the inflections of the isocheimal than by the 

 isothenxial lines ; for while two points having the same win- 



