484 GEOLOGICAL REVOLUTIONS. CHAP. 



depression was enough to bring sea- water and its drifting move- 

 ment over all but our highest hills in the chalk and oolite ranges. 

 It may have covered those highest hills, but proof fails at 750 feet, 

 according to the careful researches, which I am happy to confirm, 

 of Mr. Hull b and Mr. Lucy c . Elsewhere, as in Wales, on the 

 western border of Derbyshire, in Yorkshire, round the Lake district, 

 in Scotland, and in Ireland, the proof goes to 1500 feet ; and the 

 supposition of a merely local cause for so general an effect is 

 speedily exchanged for an admission that it extended very widely 

 round the region of the Baltic and North Germany, producing 

 everywhere a cold, even glacial sea. 



4. This remarkable phase passes ; the whole country rises again, 

 and takes so nearly its ancient position that the pre-glacial forest- 

 bed is found at about half-tide level on the eastern coast of Norfolk, 

 just as on the eastern coast of Yorkshire marshes, lakes, and forest- 

 beds of post-glacial, prehistoric, and historic date are found and 

 formed at this day. 



g-n gxv 



Diagram OCVIII. Upward and downward movement. 



If we represent by horizontal spaces the flow of geological time 

 from the era of chalk C to the modern epoch M, and by a continuous 

 curve the elevations and depressions which are admitted to have 

 happened with reference to the sea-level, the result will be such 

 a diagram as that given above. The letter S' 1 being taken to repre- 

 sent a certain point on the earth's surface, above LL the level of 

 the sea (where the first depression began after the state of previous 

 elevation of the chalk), this point would be found depressed to #", 



b Proceedings of the Geol. Soc. 1855. 



c Proceedings of the Cotteswold Club, 1869. 



