104 NATURAL HISTORY OF 



CHANGES ON THE EARTH'S SURFACE, SINCE THE COM- 

 MENCEMENT OF THE PRESENT ZOOLOGICAL BYSTEM. 



The present superficial character of the earth may be a 

 result of the combined action of sudden violent disruptions, 

 and long durations of gradual disintegrations, either 0] 

 ing as restorers of equipoises in the permanent laws of ne- 

 cessity, or as conductors of the slow process of accumula- 

 tions, which again prepare a great convulsion. Taking the 

 newer pliocene, or second tertiary age, to be coincident with the 

 mighty changes of sea and shore, when volcanic disturbances 

 were still in active operation, and that convulsive state, which 

 subsequent catastrophes, and the succession of ages, have, as 

 yet, only reduced in number, and moderated in force, when 

 first a congenial atmosphere had begun to prevail, we have an 

 epoch which would include the Mosaic deluge, and terminate 

 with that greatest of all recorded destructions, — one, moreover, 

 supported by innumerable historical confirmations, although 

 some of these may be attributed to subsequent periods, and to 

 distinct calamities, such as the bursting of the barriers of great 

 mountain lakes, and irruptions of the sea ; for these being con- 

 founded, in so man)' and remote quarters, with one great over- 

 whelming event, it is natural that the reminiscence should be 

 common to ever}- region of the world. All these, whether sud- 

 den or slow disintegrations of portions of the earth, it cannot 

 be doubted, must have had materia] influence on the distribu- 

 tion of races and human development. It is, indeed, chiefly by 

 the agency of these changes, — by the insulation of parts of 

 continents, resulting from submersions ; and, again, by the 

 expansion or rising of the submarine floor, whereon islands 

 may have stood, till they united into continents, — that many 

 of the phenomena of zoological distribution can be best 



