

MODERN GEOLOGY 



must disturb the level of the portion of the crust al- 

 ready solidified. So a plausible explanation of the 

 upheaval of continents and mountains was supplied by 

 the Plutonian theory, as Hutton had from the first 

 alleged. But now an important difference of opinion 

 arose as to the exact rationale of such upheavals. 

 Hutton himself, and practically every one else who 

 accepted his theory, had supposed that there are long 

 periods of relative repose, during which the level of the 

 crust is undisturbed, followed by short periods of active 

 stress, when continents are thrown up with volcanic 

 suddenness, as by the throes of a gigantic earthquake. 

 But now came Charles Lyell with his famous extension 

 of the "uniformitarian" doctrine, claiming that past 

 changes of the earth's surface have been like present 

 changes in degree as well as in kind. The making of 

 continents and mountains, he said, is going on as rapid- 

 ly to-day as at any time in the past. There have been 

 no gigantic cataclysmic upheavals at any time, but all 

 changes in level of the strata as a whole have been 

 gradual, by slow oscillation, or at most by repeated 

 earthquake shocks such as are still often experienced. 

 In support of this very startling contention Lyell 

 gathered a mass of evidence of the recent changes in 

 level of continental areas. He corroborated by personal 

 inspection the claim which had been made by Playfair 

 in 1802, and by Von Buch in 1807, that the coast-line of 

 Sweden is rising at the rate of from a few inches to 

 several feet in a century. He cited Darwin's observa- 

 tions going to prove that Patagonia is similarly rising, 

 and Pingel's claim that Greenland is slowly sinking. 

 Proof as to sudden changes of level of several feet, over 



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