Cornwall and South Devon. 333 



was associated with the Quantocks, it geologically appertained 

 to the Mendips, and troughed away towards them, as Mr. 

 Conybeare has long ago suggested*. In this view the Fore- 

 land or Dunkerry sandstones (No. 2.) will provisionally con- 

 stitute the mineralogical base of the entire system; these 

 are almost identical in mineral composition with the old red 

 sandstone of Monmouthshire and the Mendips, close by, and 

 are, I believe, a more southward prolongation of it. I deny 

 more confidently than ever, that there exists any axis or anti- 

 clinal line of fracture in the whole of Exmoor; every geolo- 

 gical fact, and all the associated physical evidences negative 

 such a supposition. The true mechanism of the structure of 

 Exmoor and the Quantocks is, as I announced at Liverpool 

 in 1837, that these red sandstones and shales (hitherto con- 

 taining only plants), with white quartz conglomerates, and 

 green compact calcareous grits, emerge from beneath the 

 Linton slates and the other overlying masses, and culminate 

 in three parallel mountain folds with their corresponding in- 

 verted flexures or valleys, but are finally lost on the north- 

 east of the Quantocks, where their exposed summits, barely 

 showing through the ridges of the new red sandstone in long 

 low undulations, indicate them to be rolling away towards the 

 Mendips, the mineral axis of which is old red sandstone, as 

 has been shown long since by Dr. Buckland and Mr. Cony- 

 beare f. This view of the true position of the Devonian sy- 

 stem, viz. that it occupies an enormous interval between the 

 old red sandstone and the mountain limestone, was first sug- 

 gested to me about two years ago, on observing in the neigh- 

 bourhood of Bristol a hard junction between those two for- 

 mations : subsequently I have been much gratified on finding 

 that Mr. Hopkins and Mr. Daniel Sharpe have, by indepen- 

 dent observations at different localities in the north of England, 

 remarked an unconformity also of strike and dip between 

 them. Mr. Hopkins observes, " After the elevation of the 

 older rocks, including the old red sandstone, the whole di- 



* Geology of England and Wales, — Section from the Land's-end to the 

 German Ocean. 



f It is proper to observe that a thick band of dark blue and oftentimes 

 coarse dull arenaceous limestone is included in these red sandstones in 

 Croyd hill near Minehead and along the east and north-east flank of the 

 Quantocks, very essentially differing from the cornstones or any calcareous 

 beds hitherto described as pertaining to the old red : it commonly contains 

 in its shales and planes of deposition carbonaceous matter oftentimes like 

 powdery coal smut, and as often in extremely thin films with a high metallic 

 lustre : it also contains corals in great abundance, which Mr. Lonsdale re- 

 cognised as the same species as some others he had described from the 

 lower Palaeozoic rocks of South Wales. 



