Date of the Glacial and the Upper Miocene Period. 377 



glacial epoch and the general covering of ice, the land was first 

 elevated ; and then to make matters harmonize with the facts of 

 geology, the land was submerged. 



There is no necessity for this hypothesis in order to account 

 for the cold of the glacial epoch ; and even supposing that there 

 was, it would not suit. The cold and ice of the glacial epoch 

 were too general to be accounted for upon the hypothesis of 

 elevation of the land. It is the elevation of a part in relation to 

 the surrounding continents that can cool the climate of that part 

 and cover it with ice. A general elevation would produce but 

 little effect ; for in such a case the atmosphere would to a con- 

 siderable extent rise along with the land, and no very sensible 

 change would result. We shall have to return to this part of 

 the subject on a future occasion. 



From the facts and considerations adduced we are, I would 

 venture to presume, warranted to conclude that, with the excep- 

 tion of what may have been produced by land-ice, very little in 

 the shape of boulder- clay or striated rocks belonging to the gla- 

 cial epoch lie buried under the ocean — and that when the 

 now existing land- surfaces are all denuded, probably scarcely 

 a trace of the glacial epoch will then be found, except the huge 

 blocks that were transported by icebergs and dropped into the 

 sea. It is therefore probable that we have as much evidence of 

 the existence of a glacial epoch during the Miocene, Eocene, and 

 Permian periods as the geologists of future ages will have of the 

 existence of a glacial epoch during the Posttertiary period, and 

 that consequently we have no warrant whatever to conclude that 

 the glacial epoch was a something unique in the geological his- 

 tory of our globe. 



It might be thought that if glacial epochs have been so nume- 

 rous as Table No. I. represents, we ought to have abundance of 

 palreontological evidence of their existence. I do not know if 

 this necessarily follows. Take the glacial epoch itself, quite a 

 modern affair. Here we do not require to go and search in the 

 bottom of the sea for the evidence of its existence ; for we have 

 the surface of the land in almost identically the same state in 

 which it was when the ice left it, with the boulder-clay and all 

 the wreck of the ice lying upon it. But what geologist, with all 

 these materials before him, would be able to find out from palse- 

 ontological evidence alonethat there had even been such an epoch? 

 He might search the whole, but would not be able to find fossil evi- 

 dence from which he would be warranted to infer that the country 

 had ever been covered with ice. We have evidence in the fossils of 

 the Crag and other deposits of the existence of a colder condition 

 of climate prior to^the true glacial period, and in the shell-beds of 

 the Clyde and other places of a cold condition of climate after the 



