50 Dr. Forry on the Climate of the United States, S^c, 



country rises very slowly and progressively to a height less than 

 one thousand feet. It is only when lands are considerably and 

 suddenly elevated, and exposed to the action of the atmosphere 

 laterally, that a rapid conduction of heat and rarefaction of the 

 atmosphere can take place. Our northwestern region, in those 

 districts which are remote from the great lakes, so far from caus- 

 ing a diminution of annual temperature, produces, it has been 

 seen, an augmentation. 



In regard to the extremes of heat and cold in the United States, 

 it would be natural to expect that the severest cold would be re- 

 gistered at the most northern, and the greatest heat at the most 

 southern posts. It is now, however, proved by exact instrumen- 

 tal observations that this is not the case, as these are situated on 

 large bodies of water ; but that the western stations. Forts Snell- 

 ing, Gibson, and Council Bluffs, remote from inland seas, are re- 

 markable for extremes of temperature. It is here that the mer- 

 cury rises the highest and sinks the lowest, while Forts Brady 

 and Mackinac, the most northern stations, as well as those on the 

 southern coast, exhibit a lesser range of the thermometer ; and in 

 accordance with the same law, we find that the mean summer 

 temperature is greater at Augusta, Georgia, than along the coast 

 of Florida. While at Key West, during a period of six years, 

 the thermometer never rose above 90°, it attained at Council 

 Bluffs, a point 17° 12' farther north, a height every year varying 

 from 102° to 108°. The highest temperature in the shade noted 

 at various posts, was at Fort Gibson, on the 15th of August, 1834, 

 being 1 16°. In Africa, the mercury is sometimes seen at 125°, 

 and in British India it is said to have been as high as 130°. It 

 has been remarked that on the coast of Senegal the human body 

 supports a heat which causes spirits of wine to boil, and that in 

 the northeast of Asia, it resists a cold which renders mercury 

 solid and malleable. Although the mean annual temperature, in 

 proceeding from the equator toward the poles, gradually dimin- 

 ishes, yet the thermometer scarcely mounts higher at the equi- 

 noctial line than under the polar circle. Hence it follows that 

 the climate of the tropics is characterized much more by the du- 

 ration of heat than its intensity. 



{^To he concluded in our next No.) 



