ANTIQUITY OF MAN. 243 



change becomes very great, since during some por- 

 tions of the supposed period of 200,000 years the levels 

 of sea and land must have been changing at the rate 

 of four or five feet per century, even if the process was 

 uniform, and not by successive abrupt movements, as 

 the terraces on the margins of our continents would 

 seem to indicate. But man did not, so far as known, 

 appear till the continental period, which succeeded this 

 great depression, and the changes which have occurred 

 since his advent are comparatively small, and must 

 have required a very small fraction of the time inter- 

 vening between the glacial subsidence and the present 

 time. This consideration alone, in my judgment, 

 altogether negatives the claim for such high antiqui- 

 ties, as say 100,000 years, for man. Further, the state 

 of preservation of animal remains, and the amount of 

 atmospheric erosion observed on the raised terraces, 

 at least of America, where alone I have studied them, 

 forbid so great estimates as to time. 



Again, there is reason to believe that in historical 

 times, or since the foundation of the great historic 

 empires of western Asia and northern Africa, say from 

 2,000 to 3,000 years before Christ, great areas in north- 

 ern Asia, formerly sea, have become land, and large 

 islands in the Atlantic have disappeared. The Hyr- 

 canian ocean of the ancients has been dried up, and 

 the continent of Atlantis has gone down. We have 

 already seen that the Danish shell heaps belong to the 

 later Stone age, and yet the shells found in them show 

 that they antedate the present brackish water fauna 



