Physical Structure and older stratified Deposits of Devonshire. 639 



scribed on the north-eastern flanks of the principal ridg-e. In the northern 

 portions of these hills (where they are highest and best-defined) the strike 

 conforms to their principal direction ; but further south, where they are lower 

 and more expanded, the subordinate beds undulate, and seem to lose all 

 regular bearing. 



After crossing the plain of new red sandstone, which forms the Avestern 

 side of the Quantocks, we found a repetition of nearly the same rocks, viz. 

 a series of reddish, soft slates, in some places highly calcareous, and con- 

 taining beds of limestone, resting on an inferior system of harder texture, 

 enclosing many beds of flagstone, shillat, and reddish sandstone, here and 

 there almost passing into a conglomerate form. The upper series is well 

 exhibited on the eastern skirts of Croydon HiH. The lower, with all its mo- 

 difications, is finely exposed in Croydon Hill, Grabbist Hill, and North Hill, 

 and is of very great thickness. In several parts of North Hill and Grabbist 

 Hill, the strata are violently contorted, and the lines of disturbance are in va- 

 rious directions ; yet on the whole,, the strike of the beds seems to be nearly 

 W.N.W. Part of Croydon Hill is thrown up in the form of a great elliptical 

 dome, and the calcareous bands form a portion of an elliptical curve sweeping- 

 round the eastern extremity of its longer axis ; and it perhaps deserves re- 

 mark, that the axis is nearly parallel to the principal direction of the strata in 

 North Hill and Grabbist Hill. 



In this part of Somersetshire, the strata are contorted, the hifls discontinu- 

 ous, and the sections broken ; yet the main fact, we have just stated, viz. the 

 existence of a lower formation of coarse, arenaceous rock, often of a red colour 

 and of an upper formation of calcareous slate, is established on sufficiently clear 

 evidence, and leads us at once to consider the structure of North Devon. 



The strata of North Hill are cut off" from the coast by the valley of Porlock, 

 which probably owes its origin to one of the great breaks or contortions, that 

 mark the neighbouring region. The same system of beds, however, reap- 

 pears on the west side of the bay, and is continued to a headland a little north- 

 east of Lynmouth, forming a noble succession of red cliffs, and a well-defined 

 ridge running parallel to the coast. Along the whole of this line, the beds 

 strike about W.N.W. , and dip into the sea, at a great angle, about N.N E. 



If we make a traverse to the south from any part of the coast above men 

 tioned, west of Porlock, we find at the distance of a few miles, though the 

 strike continues about W.N.W., that the prevailing dip is reversed to the 

 south. From this we discover, that an anticlinal line runs nearly parallel to 

 the strike of the beds, and to the mean direction of the coast between Porlock 

 and Countesbury Foreland. We further discover, that the mean direction of 



