EVOLUTION OF THE EARTH'S OUTLINES. 733 



of force in action had some relation to the size and depth of the 

 oceanic basin. The Pacific exhibits its greatness in the lofty moun- 

 tains and volcanoes which begirt it. 



3. In such a movement, elevation in one part supposes necessarily 

 subsidence in another ; and, while the continental was the part 

 of the crust which was elevated, the oceanic was the subsiding 

 part. 



The oscillations, plications, and elevations alluded to began in 

 the Azoic age: hence the conclusion that the oceanic basins and 

 continents were early outlined is unavoidable. The sinking of the 

 ocean's bed and the rising of the continents were concurrent effects 

 of one cause. The raising of mountains reached its climax in the 

 Tertiary period : from that time the effects have declined. 



4. If, then, the continents were from the beginning the nearly 

 stable areas (as appears also from the absence of volcanoes from 

 their interior, while they abound in the oceans), the pressure of 

 the subsiding oceanic portion has acted against the resisting mass 

 of the continents ; and thus the border between them has become 

 elevated, plicated, metamorphosed, and embossed with volcanoes. 



5. The position of the Urals between Europe and Asia is in 

 accordance with the theory ; for in a continent so broad from east 

 to west as the Orient, the tension and movements within the conti- 

 nental crust would naturally occasion some elevations. 



6. While the Alps may have been elevated by the tension within 

 the oceanic crust, the Juras appear to have been a reacting effect 

 of elevation in the region of the Alps ; for the plications are most 

 numerous towards the Alps, instead of towards the ocean. 



7. The cause of this tension and pressure within the crust has 

 been attributed, on a former page, to the secular refrigeration of 

 the globe. No other cause presents itself that can comprehend in 

 its action the whole globe and all time. 



The universality of this cause is also exhibited in the cotempo- 

 raneousness of even some of the minor oscillations of the surface 

 of different continents, — as, for example, the condition of submer- 

 gence in Europe and America preceding the Coal period, which 

 favored the formation of the Subcarboniferous limestone on both ; 

 the condition of progressing emergence required for the succeed- 

 ing Millstone grit ; and then that of the general, though slight, 

 emergence requisite for the Coal period itself (p. 394). 



It has been shown (p. 569) that after the Tertiary period the 

 system of oscillations of the earth changed to a high-latitude sys- 

 tem, both in the northern and southern hemispheres. This, again, 

 exhibits the comprehensiveness of the great cause. It is probable 



