IN THE SOUTH-WESTERN COUNTIES. 53 



attaining in some places, as by the shores of Barnstaple Bay, 100 

 feet in thickness. Whether the Head is regarded as a mere talus 

 from the weathering of adjacent exposed rock-surfaces, or as accu- 

 mulated under very different climatal conditions from those now 

 prevailing, the following observations are equally applicable : — 



First, the accumulation is not now forming to any appreciable 

 extent, judging from those exposed portions of the Palaeozoic area 

 where the accumulation of talus is now taking place. The Head 

 on the coasts is evidently the debris of a more ancient period. 



Secondly, the coast Head was accumulated after the formation 

 of the raised beaches, being alwavs uppermost when both are ex- 

 posed in the same cliff. Having observed more than thirty instances 

 of raised beach on the Cornish coast, I can verify Mr. Carne's con- 

 clusion on this point. 



Thirdly, the coast Head was formed long prior to the submergence 

 of the forests and the formation of the present Secondary cliff-line. 

 The occurrence of Head on cliffs flanked by bare rock landwards 

 where no modern talus could rest, and the isolation of rocky pedestals 

 bearing pinnacles of Head, as on Godrevy beach, Cornwall, and 

 near Start Point, South Devon, sufficiently prove this conclusion. 



Fourthly, during the accumulation of the coast Head the land 

 stood at a higher level ; for the submarine forests prove that eleva- 

 tions of at least 30 feet must have taken place prior to their growth. 

 The nature of the accumulation indicates a period of great subaerial 

 waste ; its position evidences a more extended coast line ; both com- 

 bined evidence the coexistence of a more marked or rigorous climate 

 and a greater elevation of land. 



Part II. 



All instances of terminal curvature in Devon, Cornwall, and 

 Somerset 1 ascribe to one or other of the following three distinct 

 causes : — 



The first and far the oldest of these are the great and oft-repeated 

 internal movements to which the Palaeozoic rocks were subjected. 

 The curves, flexures, and contortions produced by them being planed 

 down by denuding agents, exhibit all varieties of surface-structure, 

 one of which, resembling reversal in dip (probably in most cases 

 resulting from the denudation of an anticlinal curve), is named 

 " Terminal." Curves of this class are frequently met with in the 

 vicinity of faults. 



Examples. — The Gupworthy tunnel-section, revealing " the uniform 

 curving-back of laminae on a very gigantic scale, the vertical extent 

 of curvature amounting to at least 20 feet"*. The quarry-section 

 near Slapton (fig. 1, p. 54), and the instances mentioned by Mr. Mack- 

 intosh in the neighbourhood of Wiveliscombe, furnish examples of this 

 kind of curvature not in the immediate vicinity of faults. 



The Barnstaple and Taunton Eailway-cutting at Horridge Down, 

 near Wiveliscombe (shortly before this part of the line was opened), 



* Quart. Journ. Geol. Soc. vol. xxiii. p. 325, 



