3 1 2 Geological Society : — Prof. Sedgwick arid Mr. Murchison 



Molton, Bampton, «tid Holcombe Rogos, to the plain of the new red 

 sandstone. 



3. The third region stretches across the county ; being bounded 

 to the north by the line above indicated, and to the south by a line 

 which, commencing at Boss Castle on the coast of Cornwall, ranges 

 to the south side of Launceston, and thence in a somewhat devious 

 course to the northern edgeof Dartmoor. This southern boundary also 

 descends considerably on the east side of Dartmoor, inclosing some 

 of the country near Chudleigh. The region thus bounded is composed 

 of one great formation (occupying more than a third of the whole 

 county), to which the authors give the name of Culm Measures. 



4. The fourth region includes all the country occupied by slate 

 rocks, extending from the granite of Dartmoor and the Culm Mea- 

 sures to the south coast of Devon. 



5. The last region is occupied by the granitic rocks, which extend 

 through the whole of Dartmoor. 



Of the regions above enumerated few notices are offered respect- 

 ing the first, but the other four are described in considerable de- 

 tail, and in the above order. 



Chap. II. — Succession of deposits between the north coast of 

 Devon and the Culm Measures. 



The authors commence with a description of the rocks in the north- 

 west corner of Somerset, which are identical in structure with a part 

 of the region here described. They divide them into two great 

 groups; the lower group abounding in a coarse arenaceous strong- 

 bedded rock (grey wacke), often of a red colour, and sometimes vari- 

 egated like specimens of new and old red sandstone j the upper 

 containing some beds of like character, but abounding morein rotten 

 thin-bedded slates (shillot), in which some portions are highly cal- 

 careous, and pass into irregular bands of limestone, and contain en- 

 crinital stems and obscure traces of organic remains. They then go 

 on to describe the successive groups occupying the region of 

 North Devon, and by help of natural sections (from the coast to the 

 north boundary of the Culm Measures) prove, that there is an enor- 

 mously thick ascending series of rocks, interrupted however by nu- 

 merous contortions and by a great anticlinal line, ranging with the 

 strike of the beds, about west by north or west-north-west. This 

 line runs into the sea a little south-west of Linton, and in conse- 

 quence one of the great groups is repeated twice over ; first on the 

 coast north-east of Linton, and secondly on the coast extending from 

 the Valley of Rocks to Comb Martin. From these facts it follows 

 that the lowest rocks in North Devon are in the denudation of the 

 Lynn river, which nearly defines the position of the anticlinal region ; 

 and from the south side of that river to the Culm Measures is an 

 ascending section, interrupted only by local contortions. They then 

 describe the successive groups of the ascending section. 



1. Lowest group. Valley of the Rocks and gorge above Linton. 



The structure of this group is very varied. Some beds coarse and 

 arenaceous; others passinginto a fineglossy schist, sometimes chloritic. 

 The finer beds often contain innumerable casts of organic remains, 

 and impressions of shells are not unfrequent in the coarser arenaceous 



