CHAP, x.] CONTINUITY OF THE CHALK. 473 



newer secondary beds, although some of them, such as 

 the Alps and the Pyrenees, have received great acces 

 sions to their height in later times. All these newer 

 heds have therefore been deposited with a certain re 

 lation in position to certain main features of contour 

 which are maintained to the present day. Many oscil 

 lations have doubtless taken place since, and every 

 spot on the European plateau may have probably 

 alternated many times between sea and land; but it is 

 difficult to show that these oscillations have occurred 

 in the north of Europe to a greater extent than from 

 4,000 to 5,000 feet, the extreme vertical distance be 

 tween the base of the tertiaries and the highest point 

 at which tertiary or post- tertiary shells are found 011 

 the slopes and ridges of mountains. A subsidence of 

 even 1,000 feet would, however, be sufficient to pro 

 duce over most of the northern land a sea 100 fathoms 

 deep, deeper than the German Ocean ; and an eleva 

 tion to a like amount would connect the Shetland and 

 Orkney Islands and Great Britain and Ireland with 

 Denmark and Holland, leaving only a long deep Fjord 

 separating a British peninsula from Scandinavia. 

 When we ' bear in mind the abundant evidence 

 which we have that these minor oscillations, with a 

 maximum range of 4,000 to 5,000 feet, have occurred 

 again and again all over the world within compara 

 tively recent periods, alternately uniting lands and 

 separating them by shallow seas, the position of the 

 deep water remaining throughout the same, the im 

 portance of an accurate determination of the depth of 

 intervening sea in all speculations as to geographical 

 distribution and the origin of special fauna? becomes 

 most apparent. 



