THERMAL LIXE3 AXD ZONES. 



south side, following a sinuous and irregular course, intersecting 

 the terrestrial equator at about 100 and 160 east longitude. It 

 attains its greatest distances north at Jamaica, and at a point in 

 Central Africa, having a latitude of 15, and east longitude 10 

 or 12. The greatest mean temperature of the thermal equator 

 is 86. 



The isothermal line having the temperature of 74 is not very 

 sinuous in its course, and does not much depart from the tropics. 



12. The second zone, which is included between the isothermal 

 parallels characterised by the mean temperatures of 74 a and 68 is 

 much more sinuous, and includes very various latitudes. At the 

 points where it intersects the meridians of Europe, it is convex 

 towards the north, and attains its greatest latitude in Algeria. 



13. The third zone, included between the isothermal parallels 

 which have the mean temperatures of 68 and 59, passes over the 

 coasts of France upon the Mediterranean, about the latitude 43, 

 and from thence bends southwards, both east and west, on the 

 east towards Xangasaki and the coasts of Japan, and on the west 

 to Xatchez on the Mississippi. 



14. The fourth zone is included between the parallels of mean 

 temperatures 59 and 50. It is convex to the north in Europe, 

 including the chief part of France, and thence falls to the south 

 on both sides, including Pekin on the east, and Philadelphia, New 

 York, and Cincinnati on the west. It is evident from this 

 arrangement of the fourth thermal zone, that the climate of 

 Europe is warmer than that of those parts of the eastern and 

 western continents which have the same latitude. 



15. The fifth and sixth zones, included between the mean tem- 

 peratures of 50 and 32, are more sinuous, and include latitudes 

 more various even than the preceding. The thermometric 

 observations, however, which have been hitherto made in these 

 regions, are too limited to supply ground for any general inferences 

 respecting it. 



16. The circle whose area is comprised within the isothermal 

 parallel whose mean temperature is 32% is still less known. 

 Xevertheless, the results of the observations made by arctic 

 voyagers within the last twenty years, afford ground for inferring 

 that the mean temperature of the pole itself must be somewhere 

 from 13 to 35 below the zero of Fahrenheit, or 45 to 67 below 

 the temperature of melting Ice. 



17. AVhen it is considered how different are the vegetable 

 productions of places situate upon the same isothermal line, 

 it will be evident that other thermal conditions besides the mean 

 temperature must be ascertained before the climate of a place can 

 be known. Thus London, New York, and Pekin are nearly on 



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