570 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



group under examination. This area is occupied by varied rock 

 masses (three well-defined groups), consisting at the base of red 

 sandstone and slates with gritty and subcalcareous bands, which form 

 the Lynton or Lower Devonian series; succeeding these are red 

 sandstones and slates, well-defined calcareous masses, and bands of 

 limestone, which constitute the Middle Devonian or Ilfracombe 

 group ; these are surmounted by a thick zone of red sandstones (the 

 Upper Old lied), which are again overlain by a great series of slaty 

 subcrystalline arenaceous limestones and shales, brown sandstones 

 and grits, which constitute (with the red sandstones below) the Upper 

 Old Eed Sandstone or Upper Devonian Series, partly the equivalents 

 of those beds which occur in the Cork district, and termed by the 

 Irish geologists Carboniferous Slate, Coomhola Grits, and Old Red 

 Sandstone. It will be my object to endeavour to show that this 

 succession in North Devon and West Somerset is one unbroken and 

 continuous series, existing in both districts, and proved by physical 

 as well as palaeontological data. It will also be my endeavour 

 to prove that the hypothetical fault which Professor Jukes has 

 stated to range from Morte Bay on the west to Wivehscombe and the 

 Quantock Hills on the east has no existence through the centre of 

 North Devon, — and also to show that there is no evidence of a 

 concealed anticlinal (of the nature demanded) with a northern in- 

 version, through the agency of which, and the concealed fault with 

 a supposed northerly downthrow of some 4000 or 5000 feet, we are 

 asked to believe that the Lynton sandstones, grits, and slates, and the 

 Middle or Ilfracombe Series in the north part of the county, are 

 upon the same general horizon as those (similar, not identical) rock- 

 masses comprising the structure of Baggy Point, Marwood, Sloly, 

 Croyde, Braunton, Pilton, &c., on the south, and ahove the Pickwell 

 Sandstones. From these views I entirely dissent on the grounds 

 above stated ; and a careful examination of the "West Somerset and 

 North Devon areas during the past autumn (1866) now enables me 

 to lay before the Society the results of that investigation. 



II. HlSTOET AK^D LiTEEATTJKE, 



It is necessary to my purpose that a condensed history of the 

 literature of the Devonian Rocks, with their groupings &c., should 

 be understood, and that our British series, with their continental 

 equivalents and their correlation generally, should be paralleled ; we 

 shall thus be enabled to trace the history of the question, and aided 

 in coordinating the views held by those geologists and palaeontologists 

 who have, both in this country and on the Continent, since the 

 year 1837, adopted the nomenclature proposed by Murchison and 

 Sedgwick in their elaborate memoir upon " the Physical Structure 

 of North Devon and the Ehenish Provinces"*, in which they en- 

 deavoured to assign a position and sequence to those slates, sand- 

 stones, and limestones which are so conspicuously and extensively 

 developed in North and South Devon and Cornwall. Their views 



* Geol. Trans, vol. v. 1840; and Proceedings, vol. iii. 1839, 



