SEQUENCE OF EARTH-MOVEMENT IN BRITAIN. 347 



whether the dislocations of the Grampians and Lammermuirs, which 

 take parallel courses, were geologically synchronous or not, because 

 the beds dislocated are not the same. Even in the case of the great 

 faults which followed upon the Carboniferous system, the limits of the 

 geological epochs of their occurrence are often too vague for the ap- 

 plication of such a theory. Eothetodteliegende and magnesian lime- 

 stone cover the coal of the North of England unconformably, and thus 

 define the date of the convulsions. But in the South of England 

 these rocks are of rarer and less regular occurrence, and often entirely 

 wanting, and then the New Red Sandstone above the coal gives only 

 a vague approximation to geological time. 



Three great Groups of Earth-Movement in Britain. The sub- 

 joined diagram (fig. 72) is intended to show the directions of three 

 great movements of strata in Britain 

 which appear to be grouped in trace- 

 able systems. 



The earliest is that N.E. and .2 



S.W. system which includes Snow- \ 



donia and a large tract about it. v* v? 



By this the Cambrian strata, as \\ \ 



understood by Sedgwick (including ^'s'/ 

 the Lower Silurian of Murchison), ^tr \ 



have been much disturbed in North ^ , \ 



Wales, so that unconformity ap- 

 pears between them and the lower 

 part of the Upper Silurians. 



Another great system of move- 

 ment is typified in the North of 

 England by the great faults and 

 anticlinals of the Pennine chain, 

 varying from N.N.W. to S.S.E. 



Nearly parallel to .this are the 



dales of the Nith and the Annan, 22- 



the Dee and the Clwydd. These Fig. 72. 



dislocations precede the Whole Threc Sy8tems O f Subterranean Movement in 

 System. Britain. 



A third series of parallel or * Clyde. 8. Dee. 15. s. Wales. 



,, , . , 2- Eden. 9. Clwydd 16. N. Devon. 



nearly parallel movements affects 3 . nibble. 10. Menai. I7 . Mendip. 

 the south of Ireland, South Wales, <; Sf " $ J Icre . 



and the South Of England. In 6. Nith. 13. Bala. 20. Surrey. 



South Wales, the Mendip Hills, 7 " Ken " 22 I4 'i s Kf Wight!" S ' 

 and North Devon, it disturbs all 



the strata earlier than Permian ; and in the Isles of Purbeck and 

 Wight, and the Weald, it disturbs all the Eocene strata. This 

 appears a case of nearly the same direction, and nearly the same kind 

 of movement (anticlinals and synclinals), affecting a given district in 

 different geological times. The earlier movement was continued both 

 eastward and westward, so as to embrace a length of fully 700 miles 

 of the earth's surface from Bantry Bay to Elberfeld. The later 



