CONCLUSIONS. 387 



five hundred feet above the level of the sea ; in Norway, at 

 lat. 60, it is five thousand feet ; in the Alps, at lat. 46, about 

 eight thousand five hundred ; in the Himalaya, at lat. 30, over 

 twelve thousand ; in Mexico, at lat. 1 9, it is fifteen thousand ; 

 and at Quito, under the equator, not less than sixteen thou- 

 sand. At these elevations, in their different respective lati- 

 tudes, without taking the undulations of the isothermal lines 

 into consideration, vegetation shows a most uniform character, 

 so that it may be said that there is a corresponding similarity 

 of climate and vegetation between the successive degrees of 

 latitude and the successive heights above the sea. As a strik- 

 ing example, the fact may be mentioned of the occurrence of 

 identical plants in Lapland in lat. 67, at a height of about 

 three thousand feet and less above the level of the sea, and 

 upon the summit of Mount Washington, in lat. 44, at a height 

 of not less than six thousand feet ; while below this limit, in the 

 wooded valleys of the White Mountains, there is not one spe- 

 cies which occurs also about North Cape. 



[ 639. There is, nevertheless, one circumstance which shows 

 that climatic influences alone, however extensive, taking, for 

 instance, into account all the above-mentioned agents together, 

 will not fully account for the geographical distribution of or- 

 ganized beings ; as their various limits do not agree precisely 

 with the outlines indicating the intensity of physical agents 

 upon the surface of the earth. A few examples may serve to 

 illustrate this remark. The limit of forest vegetation round 

 the arctic circle does not coincide with the astronomical limits 

 of the arctic zone ; nor does it agree fully with the isothermal 

 line of 32 of Fahrenheit ; nor is the limit of vegetation 

 in height always strictly in accordance with the temperature, 

 as the Cerastium latifolium 'and Ranunculus ylacialis, for in- 

 stance, occur in the Alps as high as ten, and even eleven 

 thousand feet above the level of the sea. Again, eastern and 

 western countries within the same continent, or compared 

 from one continent to the other, show such differences under 

 similar climatic circumstances, that we at once feel that some- 

 thing is wanting in our illustrations, when we refer the dis- 

 tribution of animals and plants solely to the agency of climate. 

 But the most striking evidence that climate neither accounts 

 for the resemblance nor the difference of animals and plants 

 in different countries, may be derived from the fact, that the 



C c 2 



