EUROPE BEFORE ARRIVAL OF MAN 



But while the raindrops, rushing in rivers to 

 the sea, are thus with tireless industry working 

 to obliterate existing continents, their efforts are 

 counteracted, here and there, and with more or 

 less success, by slow upward thrusts or pulsations 

 from the earth's interior, which gradually raise 

 the floors of continents. The general result of 

 the struggle has been that, ever since the earliest 

 geological periods, the surfaces of the great con- 

 tinents now existing have been subject to irregu- 

 lar oscillations ; now partially or almost entirely 

 disappearing beneath the sea, now recovering 

 ground as archipelagoes, or rising high and dry 

 to great elevations, as in the case of Africa. The 

 oscillations have not ordinarily exceeded from 

 6000 to 10,000 feet in vertical extent. There is 

 no reason for supposing that the general relative 

 positions of the great continents and great oceans 

 have altered at all since the beginning of the 

 Laurentian period. Since life began on the earth 

 there is no reason for supposing that the bottoms 

 of the stupendous abysses which hold the waters 

 of the Atlantic, the Pacific, and the Indian oceans 

 have ever been raised up so as to become dry 

 land. Once geologists thought otherwise, and 

 land was turned into sea and sea into land, by 

 facile theorizers, as often as it was supposed to be 

 necessary to account for the distribution of cer- 

 tain lizards or squirrels, or for changes in climate, 

 such as have left marks behind in many parts of 

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