128 SCIENCE IN SHORT CHAPTERS. 



during the glacial epoch, to the extent of 600 feet as a 

 minimum, while the well-known deposits of Arctic shells 

 at Moel Tryfaen and the accompanying drift have led Prof. 

 Ramsay to estimate "the probable amount of submergence 

 during some part of the glacial period at about 2300 

 feet." * 



It would be out of place here to reproduce the data upon 

 which geologists have based their rather divergent opinions 

 respecting the actual extent of the submergence of the 

 western coast of North Europe. All agree that a great 

 submergence occurred, but differ only as to its extent, their 

 estimates varying between 1,000 and 3,000 feet. 



There is one important consideration that must not be 

 overlooked, viz., that if my view of the submarine origin 

 of the till be correct the mere submergence of the land at 

 the glacial period does not measure the difference between 

 the depth of the sea at that and the present time, seeing 

 that the deposits from the glaciers must have shallowed it 

 very materially. 



It is only after contemplating thoroughly the present 

 form of the granitic and metamorphic hills of Scandinavia, 

 hills that are always angular when subjected only to sub- 

 aerial weathering, that one can form an adequate con- 

 ception of the magnitude of this shallowing deposit. The 

 rounding, shaving, grinding, planing, and universal abra- 

 sion everywhere displayed appear to me to justify the con- 

 clusion that if the sea were now raised to the level of the 

 terraces, i.e., 600 feet higher than at present, the mass of 

 matter abraded from the original Scandinavian mountains, 

 and lying under the sea, would exceed the whole mass of 

 mountain left standing above it. 



The first question suggested by reading Mr. Geikie's 

 book was whether the terraces are wholly or partially 

 formed of till, and more especially whether their lower 

 portions are thus composed. This, as already stated, was 

 easily answered by the almost unanimous reply of all the 

 many Norwegian valleys I traversed. Any tourist may 

 verify this. The next question was whether this same tifi 



*Lyell, "Elements of Geology," p. 159. 



