214 NEOZOIC TIME. [CHAP. XI. 



coast-lines of Wales and other hilly districts, yet we must 

 suppose that the great sheets of Chalk which occupied the 

 intervening tracts suffered but little, and formed broad 

 plains uniting Wales to the Pennine range and Ireland to 

 England and Scotland. 



The materials of which the Eocene and Oligocene strata, 

 consist are such as are derivable from the Chalk and from 

 the granitic and Palaeozoic rocks of the western districts. 

 It would seem, indeed, that they were derived from these 

 sources only, for not a chip or pebble of any Jurassic rock 

 has been found in them ; and there is therefore every 

 reason to suppose that the Jurassic, and probably the 

 Lower Cretaceous strata also, were deeply buried through- 

 out the duration of the Hantonian period. 



As regards the general elevation of the country above 

 the sea at this epoch, if we bear in mind that the deepest 

 part of the Cretaceous sea lay over eastern England, and 

 the probability that Ireland was never so deeply sub- 

 merged as England, we may conclude that the elevation 

 which raised the eastern part of England into land must 

 have carried Ireland and West Scotland to a much higher 

 level above the sea than that at which they now stand. It 

 is quite possible that there was a difference of 500 fathoms 

 in the depth of the Cretaceous sea along the eastern and 

 western parallels of the British area, and if the subsequent 

 upheaval was approximately uniform, the upper surface of 

 the Irish Chalk would on these assumptions have been 

 raised to a level of 3,000 feet above the sea when the 

 Chalk of eastern England was raised to the sea-leveL 

 Moreover, it is a remarkable fact that our islands are 

 shown by the Admiralty charts to stand upon a submarine 

 plateau, the border of which runs outside the coasts of 

 France, Ireland, and the Hebrides; on this plateau the 

 soundings are everywhere under 100 fathoms (600 feet), 

 but from its surface the sea-bottom slopes steeply down 



