Physical Structure and older stratified Deposits of Devonshire. 641 



or the outskirts of a physical region (such, for example, as the termination of 

 the old rocks of Somerset and Devon, in the plain of the new red sandstone) 

 is often marked by the greatest possible confusion, both in the direction and 

 dip of the strata. The reason of this is obvious; for in such situations, the 

 strata are exhibited in the very regions, in which antagonist forces werejust on 

 the point of overcoming those very forces from which the chains themselves, 

 and all their accidents, were originally derived. This remark is, we think, 

 well illustrated by the irregular undulations of North Hill, the interruption of 

 Porlock Bay, the dome-like elevation of Croydon Hill, and, perhaps we may 

 add, by the outlying ridge of the Quantocks. 



It appears from what we have stated, that the lowest beds in this part of 

 North Devon must be sought in the anticlinal region, and in the deep gorge 

 of the Lyne. Accordingly, we there find a gradual passage into a lower sy- 

 stem of soft, chloritic, fossiliferous slates, alternating with many harder, arena- 

 ceous bands. The upper part of the group is seen in the horizontal beds 

 of the Valley of Rocks ; the lower portion only in ascending- the deep cleft 

 of the Lyne. It is interesting, as forming the base of the old rocks of North 

 Devon, and as being the lowest fossiliferous and calcareous slaty group ; but 

 its whole thickness is nowhere exposed to view, and we are left to other evi- 

 dence as to its place in a descending series of formations. 



We ha^re before stated, that the red arenaceous system, with a steady dip 

 (about S. by W., or S.S.W.), extends from the Valley of Rocks to Combe 

 Martin. Just as we turn the headland leading into the Combe, a new group 

 presents itself, constituting a succession of cliffs of different colour and form, 

 the highest beds of which run into the sea about a mile west of Ilfracombe 

 Harbour. This group, near the coast, contains eight or nine distinct calcareous 

 bands, some of which are extensively worked for use ; and many parts of it are 

 highly fossiliferous. Its average breadth is about a mile and a half, measured 

 horizontally and in a direction transverse to the strike ; and it may be traced 

 without difficulty into the interior (especially by help of the calcareous bands), 

 first in a direction about S.S.E., then along the south flank of Exmoor Forest, 

 in a direction nearly east and west. We afterwards meet with it along the 

 water-shed crossing the turnpike-road from Minehead to Dulverton ; and from 

 that point (as before stated) it forms a great elliptical curve, sweeping round 

 the eastern and north-eastern flanks of Croydon Hill. In this way we have a 

 complete proof that the calcareous slates of Somersetshire, bordering on the 

 Croydon hills, are the equivalents of those at Ilfracombe; and that the coarse 

 red greywacke of Croydon Hill is also the equivalent of the red beds of the 

 same structure on the coast between Combe Martin and the Valley of the 



