of the Surface of the Earth. lib 



cause we are not able to detei'mine them, and because, in so 

 far as our comprehension is concei'ned, they are removed 

 from the sphere of necessity ; and, in the second place, the 

 forces acting at the surface, of which volcanic eruptions, 

 earthquakes, and the production of mountain-chains and ma- 

 rine curi'ents, have performed the chief part. How entirely 

 different would the condition of the temperature of the earth, 

 and with it that of vegetation, of agriculture, and of human 

 society, have been, if the principal axis of the new Continent 

 had been placed in the same position as that of the old, — if 

 the chain of the Andes, instead of having a meridian-like di- 

 rection, had risen up from the east towards the west, — if to 

 the south of Europe there had been no tropical land (Africa) ra- 

 diating heat, — if the Mediterranean Sea, which, at one period 

 stood in connection with the Caspian and Red Seas, and exer- 

 cised so powerful an influence oa the progress of human civi- 

 lization, had not existed, — and if the bottom of that sea had 

 been elevated to the same height as the plains of Lombardy 

 and Cyrene ! 



The changes in the relative heights of the liquid and 

 solid portions of the surface of the earth (changes which, 

 while they determine the outlines of the continents, lay di'y 

 or submerge the low lands) are to be ascribed to the action 

 of many non-contemporaneous causes. The most power- 

 ful of these have undoubtedly been the force of the elastic 

 vapours which are contained in the interior of the earth ; the 

 sudden alteration of the temperature* of immense beds of 

 rock ; the unequal secular loss of heat of the crust and nu- 

 cleus of the earth, produced by an elevation (literally folding 

 or wrinkling — Faltimg ovRunselung) of the solid surface; and 



* De la Beche's Sections and Views, 1830, Plate xl. ; and Babbage's 

 Observation on the Temple of Serapis, 1834. " A mass of sandstone, 

 five English miles in thickness, when heated to 1CM3° Fahr., would have 

 its surface raised to an extent of 25 feet. Heated strata of clay, on the 

 other hand, must, by contraction, produce a sinking of the surface." 

 Vi'k the calculations as to the secular rising of Sweden, on the supposi- 

 tion of the small increase of 3°. R., in a mass of rock 140,000 French 

 feet thick, heated to the melting point, in Bischof s Wiirmckhrc dcr In" 

 nern unsercs Erdkiirjjcrs, p, 303. _j 



