64-2 Professor Sedgwick and R. I. Murchison, Esq., on the 



Rocks. This is precisely the same conclusion which we attain,, in a different 

 way, by first identifying the formations of Croydon Hill with those of North 

 Hill, and so linking them with the coarse red rocks of the Devon coast, on 

 the north side of the great anticlinal line of the Lyne*. The identification 

 of the Ilfracombe system with the calcareous bands on the north-east flanks of 

 the Quantocks, is not so complete; but it is, we think, highly probable, both 

 from the lie of the country and the structure of the component beds. We have 

 been the more particular in the preceding account, because it seems necessary 

 to a clear understanding of the stratification of the region, and of the evidence 

 presented by our transverse section. 



The calcareous slate system of Ilfracombe, though interrupted by some vio- 

 lent contortions, dips, on the whole, to a point a few degrees west of south ; 

 and is succeeded, in the ascending order, by a great formation of rocks, in 

 which a slaty character predominates more decidedly than in any of the pre- 

 ceding systems. This slate group generally dips at a high angle, and is of 

 very great thickness ; less, however, than might at first be supposed from its 

 breadth, which is not less than four or five miles, inasmuch as many of its 

 beds are repeated again and again by a succession of anticlinal and synclinal 

 planes, ranging exactly with the strike of the country. It may be separated into 

 two natural divisions : the lower abounding in a greenish chloritic schist, 

 much intersected by quartz veins, and generally too soft and shivery to be 

 used for roofing-slate ; the upper containing also many soft fissile beds, resem- 

 bling those just mentioned, but abounding also in thick, arenaceous beds, some 

 of which are red and variegated, like the hard arenaceous bands east of Combe 

 Martin, while others are gray and greenish gray. The glossy slates of the lower 

 division terminate on the coast near the north end of Morte Bay ; and some 

 hard, greenish gray, or purple, micaceous flagstones, form the highest por- 

 tions of the upper division, and are, by a well-defined southern dip, carried 

 under the next succeeding headland of Baggy Point. 



* If we are correct in identifying the red sandstones and hard arenaceous rocks of Croydon 

 Hill, Grabbist Hill, and North Hill ; and if we have correctly linked the rocks of North Hill with 

 the red arenaceous rocks which strike from Porlock Bay to the Foreland ; it then follows inevitably, 

 that the red sandstone of the Foreland is the equivalent of the red sandstone between the Valley 

 of Rocks and Combe Martin. Mr. De la Beche (Report on the Geology of Devon and Cornwall, 

 1839) places the red sandstone of the Foreland under the Linton system. We cannot at present 

 accept this interpretation of what we allow to be a difficult and disturbed natural section. Our 

 interpretation of the phenomena is explained in the text, and illustrated by the accompanying 

 section (PI. LI. fig. 1.). The question is, fortunately, one of no real moment, as tliere is now no 

 difference of opinion respecting the geological position of the several groups of strata with organic 

 remains, upon which all general questions of classification must ultimately depend. 



