282 NEOZOIC TIME. [CHAP. XIII. 



creasing and advancing he does not think any Boulder- 

 clay would be formed, but when it ceased to move and 

 began to melt, the load which it carried would be gradually 

 deposited, and most of it would eventually settle down on 

 the surface over which the ice came to rest. Melting would 

 go on over both the lower and the upper surfaces of the 

 ice, which, though ceasing to glaciate, would still exercise 

 great vertical pressure, compacting the material thawed 

 out of its lower layers into Boulder-clay, except here and 

 there where this might undergo a rearrangement by sub- 

 glacial streams. 



Mr. G-oodchild only applies this hypothesis to the Drifts 

 of mountain districts, and does not seem to have considered 

 what might take place in those areas where the ice had 

 usurped the place of the sea. Indeed, he is needlessly 

 sceptical about the submergence which even the most ex- 

 treme glacialists are prepared to admit ; but it would 

 probably repay anyone who was studying an area where 

 marine Drifts abutted against a mountain district to con- 

 sider whether some modification of Mr. Goodchild's hypo- 

 thesis would not explain the intercalation of marine sands 

 and shelly Boulder-clays. 



With regard to the Glacial deposits of England and Ire- 

 land, the hypothesis which assumes that the Boulder-clays 

 were laid down on an actual land surface is still more inap- 

 plicable than in the case of Scotland. The proofs of the 

 presence of sea-water are much more apparent and uni- 

 versal ; the Glacial deposits extend over much broader 

 areas of comparatively low ground, and though a certain 

 kind of succession can be made out in some localities, there 

 is nothing like the definite arrangement of Boulder- 

 clays which Professor J. Geikie has assumed, and which 

 three or four distinct ice- sheets ought certainly to have 

 produced. 



To commence with the oldest or Cromer Drifts, the 



