CLOSE OP POST-PLIOCENE — ADVENT OP MAN. 291 



Very important questions of time are involved in 

 this idea of Post-glacial man, and much will depend, 

 in the solution of these, on the views which we adopt 

 as to the rate of subsidence and elevation of the land. 

 If, with the majority of British geologists, we hold 

 that it is to be measured by those slow movements 

 now in progress, the time required will be long. If, 

 with most Continental and some American geologists, 

 we believe in paroxysmal movements of elevation and 

 depression, it may be much reduced. We have seen 

 in the progress of our inquiries that the movements 

 of the continents seem to have occurred with acceler- 

 ated rapidity in the more modern periods. We have 

 also seen that these movements might depend on the 

 slow contraction of the earth's crust due to cooling, 

 but that the effects of this contraction might manifest 

 themselves only at intervals. We have further seen 

 that the gradual retardation of the rotation of the 

 earth furnishes a cause capable of producing eleva- 

 tion and subsidence of the land, and that this also 

 might be manifested at longer or shorter intervals, 

 according to the strength and resisting power of the 

 crust. Under the influence of this retardation, so 

 long as the crust of the earth did not give way, the 

 waters would be driven toward the poles, and the 



the author of Genesis in his work. The dates of the rising and 

 fall of the water, the note of soundings over the hill-tops when 

 the maximum was attained, and many other details, as well as 

 the whole tone of the narrative, seem to require this supposi- 

 tion, which also removes all the diflBculties of interpretation 

 which have been so much felt. 



