Geological Society. 285 



band of transition limestone imbedded in the upper portion of these 

 older formations : and from the phenomena described, certain facts 

 (important in the physical history of the mountain groups) become 

 securely established. 



1. Great cracks were formed at a very ancient epoch, and probably 

 during the first period of elevation, diverging from the central regions 

 of the Lake Mountains ; and such enormous shifts took place in the 

 position of the shattered strata, that in several instances the broken 

 ends of the same bed are more than a mile apart, the distance being 

 measured in a direction at right angles to the lines of bearing. In 

 after periods many of the existing valleys were scooped out upon the 

 lines of fracture. 



2. The central schistose groups abut in succession against the car- 

 boniferous zone ; and from this fact alone (independently of many 

 others bearing upon the same point), the two systems are proved to 

 be unconformable. 



3. The mean bearing of the great central groups, notwithstanding 

 their enormous dislocations, is, with very slight deviations, north-east 

 by east, and south-west by west. Now this is nearly the mean bear- 

 ing of the slate rocks of Cornwall, of the principal greywacke' chains 

 of Wales and of the Isle of Man, and also of the entire greywackd 

 chain extending across the South of Scotland, from St. Abbs Head to 

 the Mull of Galloway : and it is, I believe, generally allowed, that 

 these several chains, producing so great an impress on the phy- 

 sical character of our island, are all nearly of one age, and were pro- 

 bably all elevated nearly at the same period, before the complete de- 

 velopment of the old red sandstone. Such a parallelism cannot surely 

 be regarded as accidental, and offers, if I mistake not, a beautiful 

 confirmation of the great principle in the late Essay of M. Elie de 

 Beaumont, that mountain chains elevated at the same period of 

 time have a general parallelism in the bearing of their component 

 strata. In admitting such a principle, we must not however shut our 

 eyes to the exceptions. Mr. Weaver has shown, that the mean bear- 

 ing of the greywack^ strata in the South of Ireland is east and west j 

 and from his descriptions they appear to have been elevated before 

 the deposit of the old red sandstone. The transition rocks of Devon- 

 shire and of a small portion of South Wales are nearly in the same 

 direction, and parallel to the principal axis of the great Welsh coal- 

 field. 



I will not detain you, Gentlemen, with my speculations on the 

 original extent of our carboniferous formations on the different 

 periods of elevation of the coal-fields on the Bristol Channel and of 

 the great carboniferous chain of the North of England on the diffe- 

 rent effects produced by the two systems on the range of the newer se- 

 condary groups or on the causes by which the conflicting phenomena 

 have been brought about. I may however be permitted to remind you 

 of the prevailing north and south bearings of the great carboniferous 

 chain, from the latitude of Derby to the border of Scotland of the 

 great faults by which its western limits are tracked through the Peak 

 of Derbyshire of its prolongation through an anticlinal line into the 



high 



