242 FOSSIL MAN. 



in the north of Europe and Asia very important 

 physical changes have occurred in what are properly 

 historic times, and which may serve to give us some 

 measure for the time necessary, at the same rate, for 

 those which preceded them ; and (2) That the rate of 

 change in historic times is not a certain measure of 

 that in pre-historic periods ; but on the contrary, that 

 there are indications of more rapid changes before the 

 dawn of history, and in the early human period. 



1. With reference to the great physical changes 

 known to have occurred in historic times, I may 

 refer to the fact that it is proved by the occurrence of 

 marine shells and sea beaches at great elevations, that 

 much of the land of the northern hemisphere was 

 depressed under the sea to the amount of from 2,000 

 to 4,000 feet in the later Glacial period, f Evidence of 

 this is accumulating from Great Britain, Scandinavia, 

 eastern and western America. Now, the close of the 

 Glacial age has been estimated on various data at 

 from 7,000 * to 200,000 J years ago. If we take even 

 the longest of these periods, and suppose that during 

 some considerable part of it the land has remained in 

 a state of repose, or the sea at the same level, the rate 

 of depression and elevation required for this enormous 



* Andrew's calculations, based on the lake terraces of North 

 America, give from 7,000 to 20,000 years. WincheH's, on the 

 Falls of St. Anthony, in connection with the occurrence of our 

 winter in aphelion 11,300 years ago, give 8,859 years. 



f No. 2 of Table. 



J droll's calculations, based on precession of the equinoxes 

 and eccentricity of the earth's orbit, and accepted by Lyell and 

 others. 



