292 THE STORY OF THE EARTH AND MAN. 



northern land would be submerged ; but so soon as 

 the tension became so great as to rupture the solid 

 shell, the equatorial regions would collapse, and the 

 northern land would again be raised. The subsidence 

 would be gradual, the elevation paroxysmal, and 

 perhaps intermittent. Let us suppose that this was 

 what occurred in the Glacial period, and that the 

 land had attained to its maximum elevation. This 

 might not prove to be permanent; the new balance 

 of the crust might be liable to local or general 

 disturbance in a minor degree, leading to subsidence 

 and partial re-elevation, following the great Post- 

 glacial elevation. There is, therefore, nothing un- 

 reasonable in that view which makes the subsidence 

 and ^ re- elevation at the close of the Post-glacial 

 period somewhat abrupt, at least when compared 

 with some more ancient movements. 



But what is the evidence of the deposits formed at 

 this period ? Here we meet with results most diverse 

 and contradictory, but I think there can be little 

 doubt that on this kind of evidence the time required 

 for the Post-glacial period has been greatly exagger- 

 ated, especially by those geologists who refuse to 

 receive such views as to subsidence and elevation as 

 those above stated. The calculations of long time 

 based on the gravels of the Somme, on the cone of 

 the Tiniere, on the peat bogs of France and Denmark, 

 on certain cavern deposits, have all been shown to be 

 more or less at fault ; and possibly none of these 

 reach further back than the six or seven thousand 



