334 COSMOS. 



valleys, or according to the effects of the hypsometrical relation' 

 on their own summits, which often spread into elevated pla- 

 teaux. The division of mountains into chains separates the 

 earth's surface into different basins, which are often narrow 

 and walled in, forming cauldron-like valleys, and (as in Greece 

 and in part of Asia Minor) constitute an individual local cli- 

 mate with respect to heat, moisture, transparency of atmo- 

 sphere, and frequency of winds and storms. These circum- 

 stances have, at ali times, exercised a powerful influence on 

 the character and cultivation of natural products, and on the 

 manners and institutions of neighbouring nations, and even 

 on the feelings with which they regard one another. This 

 character of geographical individuality attains its maximum, 

 if we may be allowed so to speak, in countries where the dif- 

 ferences in the configuration of the soil are the greatest possi- 

 ble, either in a vertical or horizontal direction, both in relief 

 and in the articulation of the continent. The greatest con- 

 trast to these varieties in the relations of the surface of the 

 earth are manifested in the Steppes of Northern Asia, the 

 grassy plains (savannahs, llanos, and pampas) of the New 

 Continent, the heaths (Ericetd] of Europe, and the sandy and 

 stony deserts of Africa. 



The law of the decrease of heat with the increase of eleva- 

 tion at different latitudes is one of the most important subjects 

 involved in the study of meteorological processes, of the 

 geography of plants, of the theory of terrestrial refraction, 

 and of the various hypotheses that relate to the determina- 

 tion of the height of the atmosphere. In the many moun- 

 tain journeys which I have undertaken, both within and 

 without the tropics, the investigation of this law has always 

 formed a special object of my researches. * 



Since w r e have acquired a more accurate knowledge of the 

 true relations of the distribution of heat on the surface of the 

 earth, that is to say, of the inflections of isothermal and iso- 

 theral lines, and their unequal distance apart in the different 

 eastern and western systems of temperature in Asia, centra] 

 Europe, and North America, we can no longer ask the 



* Humboldt, Recueil d 'Observations astronomiques, t. i. pp. 126-140; 

 Relation liistorique, t. i. pp. 119. 141, 227; Biot, in Connaissance cfca 

 letups pour I'an 1841, * . 00-109. 



