THE HUMAN SPECIES. 25 



remote quarters, with one great overwhelming event, 

 it is natural, that the reminiscence should "be common 

 to every region of the world. All these, whether 

 sudden or slow disintegrations of portions of the earth, 

 it cannot be doubted, must have had material influence 

 on the distribution 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 pheno- 

 mena of zoological distribution can be best explained ; 

 and if this observation is accepted with respect to brute 

 mammalia, it surely implies that man, at least in some 

 degree, may have had to encounter similar contin- 

 gencies. 



In order to appreciate the great changes proved, or 

 asserted to have occurred, let us take a short review of 

 those which are the most prominent in the physical 

 history of the earth. 



