South We item Part of Somersetihire, 355 



Withycombe farm and Countesbury to Linton, and from thence 

 through the Valley of Rocks by Slattenslade, Trentishoe, Combe 

 Martin and Berry Narbor to Ilfracombe. A very great part of this 

 country is entirely concealed by vegetation, but wherever the rock is 

 exposed I found some variety of the grauwacke formation identical 

 with those I had left behind. In that part of the road which is east- 

 ward of Linton, the coarser grained varieties are most frequent, but 

 westward of that place the slaty varieties predominate, very often 

 resembling some kinds of iron-grey clay-slate found in primary 

 countries. Towards Ilfracombe this appearance becomes still more 

 decided, and in a cabinet specimen it would be impossible to tell 

 the difference. But beds of limestone with very decided indications 

 of organic remains contained in this slate, show that it is of secon- 

 dary formation, and at the same time afford a useful lesson of the 

 inadequacy of mineralogical characters alone to determine the 

 geological nature of a rock. These limestone beds are found 

 between Berry Narbor and Hele ; their resemblance to those I have 

 described in the former part of this paper both in internal com- 

 position and in the accompanying slate, leave no doubt of their 

 belonging to the same class. When struck with a hammer it emits 

 a slight bituminous smell, a circumstance which I did not observe 

 in the limestone of the other places I have mentioned, and it is 

 traversed by very large veins of a transparent and very beautiful 

 calcareous spar. 



§ 20. Throughout the whole district described in this paper 

 I found the grauwacke formation surrounded either by a conglo- 

 merate, or by a red sandstone, sometimes tolerably compact, but 

 more frequently of a friable texture. These conglomerates and 

 sandstones assume very various appearances, but under every form 

 of aggregation the same materials may be traced. Where the 



2 y 2 



