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330 TYNEDALE ESCAEPMENTS ; 



How long lias the river system had to work in ? How long is 

 it since this neighbourhood of the backbone of England was part 

 of a plain of marine denudation new raised above the sea ? 



Although theoretically it may not seem so, it is practically un- 

 necessary to have the question of a ''great submergence" during 

 the glacial period decided. The traces of it are so few and far 

 between as to make it possible for excellent geologists to hold 

 that it never occurred at all. Evidence is too strong to admit 

 of any doubt that the figure of the country was only modified in 

 some details by the total glacial period, and in view of that fact 

 it matters little to this subject whether it included a submer- 

 gence or not. 



Passing from it the question arises — To what extent if at all 

 have these carboniferous regions been buried beneath marine 

 deposits now removed? and with it is linked another — In how 

 far can the negative evidence that a formation is absent be relied 1 

 on as positive evidence that it was never there ? 



A severe shake has undoubtedly been given to assumptions of 

 this negative kind by the very able researches of Professor Judd 

 on the Secondary Strata in Scotland. The scraps of secondary! 

 formations which dot the geological map of Scotland have been 

 preserved only by the most curious accidents. Powerful disloca- 

 tions, sometimes, have fixed them deep down in niches among 

 older rocks ; enormous sheets of Tertiary lavas, now themselves, 

 at best, only rags and shreds of what they were, have overspread 

 them and preserved portions underneath ; and but for such rare 

 chances, geologically speaking, these ''fragments of a world" 

 might well have " left not a wreck behind." To use a homely 

 illustration, the exposed remains of them bear no larger propor- 

 tion to the country where they appear than do the black specks 

 you may see in notches of the cut-glass ware of uncareful house- 

 keepers, and all about them where scruhhng could reach has been 

 washed and scoured. The most recent of the fragments belongs 

 to the Cretaceous : and there is concurrence of opinion by such 

 authorities as Ramsay* and Judd,t putting the Older Secondary 



* Phys. Geol. and Geog. of Great Britain, 5th Edition, p. 253. 

 1 Quart. Jour. Geol. Soc, 1878, p. 669. 



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