GENERAL RETROSPECT. 321 



nuity of man cannot pass, but there is no possible end to 

 his extirpations and modifications; and thus in the lapse of 

 time the natural course of vital development and distribu- 

 tion will be extensively interfered with by the operations 

 of man. But extensive as may be his interference, he can- 

 not overrule the great Law of Progression any more than he 

 can prevent the physical operations by which the continents 

 themselves are continually modified. The law will go irre- 

 sistibly forward, carrying man in his several varieties along 

 with it ; employing, it may be, his influence as a pre-ordain- 

 ed portion of its operations, but still methodically ascending 

 from higher to higher, till the future aspects of life differ as 

 widely from those of the present, as its present aspects differ 

 from those that preceded. 



Such are the leading features of the future, which, rea- 

 soning from the order of the past and the appointments of 

 the present, Geology is enabled to indicate new distribu- 

 tions of sea and land, new climates and physical surround- 

 ings, new and higher orders of plants and animals ; but 

 all these brought about so slowly and gradually that the 

 changes become apparent only after the lapse of ages. The 

 present, so far as we can judge, is as fluctuating as the past, 

 and yet the oldest scenes of human history India, Meso- 

 potamia, the valley of the Nile, the shores of the Levant, 

 Greece, and Italy remain in all their broader features 

 much as they were three thousand, four thousand, and six 

 thousand years ago. So tranquil, indeed, are the great 

 physical progressions of nature that it requires some mental 

 effort to perceive them ; so gradual the vital, and through 

 so many intermediate stages, that it demands an exercise of 

 reason to admit their reality. But when once perceived, 

 how enlarged our conceptions of the universe a system of 

 incessant fluctuation and progress in its details ; a system 



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