CLIMATOLOGY. 



331 



tion,* we begin with those plants which require the hottest 

 climate, as the vanilla, the cacao, banana, and cocoa nut, 

 and proceed to pine apples, the sugar cane, coffee, fruit-bear- 

 ing date trees, the cotton tree, citrons, olives, edible chesnuts, 

 and vines producing potable wine, an exact geographical con- 

 sideration of the limits of cultivation, both on plains and on 

 the declivities of mountains, will teach us that other climatic 

 relations besides those of mean annual temperature are in- 

 volved in these phenomena. Taking an example, for instance, 

 from the cultivation of the vine, we find that, in order to pro- 

 cure potable wine,f it is requisite that the mean annual heat 



* Humboldt, op. cit., pp. 156-161 ; Meyen, in his Orundriss der 

 Pftanzengeographie, 1836, s. 379-467; Boussingault, Economic rurale, 

 t. ii. p. 675. 



+ The following table illustrates the cultivation of the vine in Europe, 

 and also the depreciation of its produce according to climatic relations. 

 See my Asie centrale, t. iii. p. 159. The examples quoted in the text 

 for Bordeaux and Potsdam, are, in respect of numerical relation, alike 

 applicable to the countries of the Rhine and Maine (48 35' to 50 7' N. 

 lat.). Cherbourg in Normandy, and Ireland, show in the most re- 

 markable manner how, with thermal relations very nearly similar to 

 those prevailing in the interior of the Continent, (as estimated by the 

 thermometer in the shade,) the results are, nevertheless, extremely 

 different, as regards the ripeness or the unripeness of the fruit of the 

 vine ; this difference undoubtedly depending on the circumstance, 

 whether the vegetation of the plant proceeds under a bright sunny sky. 

 or under a sky that is habitually obscured by clouds : 



