202 OBSERVATIONS ON THE MEAN TEMPERATURE 



This gradation of" temperature, so obvious to the sensations 

 of those who have visited southern climates, is still more dis- 

 tinctly indicated by its physical and moral influence. The 

 arid plains of a tropical climate, where vegetable life is almost 

 extinguished by excessive heat, gradually shades into the more 

 luxuriant regions of the vine and the olive. The mild and 

 uniform temperatures of Spain and Italy, are again followed 

 by the variable climate, and the more verdant kingdoms in the 

 north of Europe. Then succeeds the region of blighted vege- 

 tation, where nothing can exist but the birch and the pine, and 

 the chain of vegetable life terminates in the hoary desolation 

 of the Arctic Zone. 



The progression of climate is no less distinctly marked by 

 the developement of the human faculties. Indolent and im- 

 patient of thought under the debilitating influence of a sultry 

 atmosphere, man begins to unfold his capacities as he is remo- 

 ved from the Torrid Zone. In more temperate climates, he 

 cultivates those faculties which do not lead to very rigorous 

 application ; and under the invigorating influence of a colder 

 sky, the mind attains that maturity of its powers, which fits it 

 for the most abstract and profound speculations. From this 

 region, distinguished as the seat both of ancient and modern 

 civilisation, the mind again sinks under the torpor of extreme 

 •cold, and the distinctive characters of our species disappear 

 among the diminutive inhabitants of the Polar latitudes. 



The investigation of the mean temperature of the Earth, 

 connected, as it thus appears to be, with many interesting in- 

 quiries of a moral and physical nature, has not been pursued 

 with the same zeal as other branches of knowledge. Long af- 

 ter the invention of the thermometer, no attempt had been 

 made to apply it to meteorological purposes ; and though, for 

 more than half a century, its indications have been registered 



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