Dr Forry on the Climate of the United States. 103 



it is found in our excessive climates, compared with the 

 modified, that the annual temperature gains more by the 

 continued elevation of the thermometer in summer, than 

 it loses by its depression in winter. Besides, in excessive 

 climates, the vernal increase alone often compensates for the 

 low temperature of winter ; for example, although the mean 

 winter temperature at Fort Sullivan is 22''-95, and at Fort 

 Snelling as low as IS^-OS, yet that of spring is higher at the 

 latter, being as 46°-78 to 40°-ll. Then follows a mean sum- 

 mer temperature more than 10° higher in the excessive than 

 in the uniform clime. The season of autumn (September, 

 October, and November) is not perceptively influenced by 

 these causes. 



These contrasts would be still more striking were the 

 comparisons instituted between points on the same isother- 

 mal line, instead of the same parallel of latitude ; for, as 

 the isothermal curve of Fort Sullivan would strike a point 

 at least 2° north of Fort Snelling, the extremes of the seasons 

 there would be cori'espondently augmented. Sufficient, 

 however, has been adduced to prove, that Humboldt's de- 

 duction, that the same causes which produce the greatest con- 

 vexitti of the isothermal line, also equalize the temperature of 

 the seasons, is unwarranted as a general law. And here the 

 writer may venture to add that these conclusions pertain 

 wholly to himself, inasmuch as they had been, doubtless, 

 never brought to the notice of the scientific world, before 

 they were made known by him in his work on " The Climate 

 of the United States, and its Endemic Influences." 



Tliese results, in the comparisons just made, appear the 

 more exti*aordinai'y, as some reduction of temperature, by 

 reason of the elevation of these interior posts, would be d 

 priori inferred ; for, accoi'ding to Humboldt, " elevations of 

 four hundred metres, (one thousand three hundred and 

 twelve feet,) appear to have a very sensible influence on the 

 mean temperature, even when great portions of countries rise 

 progressively.^'' That high table-lands have a more exalted 

 temperature than isolated mountains of the same height is well 

 ];nown ; for the elevated plains on which the towns of Bogota, 

 Popayan, (jjuito, and Mexico are built, have a much warmer 



