1866.] JUKES OLD RED SANDSTONE AND DETONIAN. 857 



on the upper surface of the bed, I saw at once that the little ridge was the top of a 

 sharp anticlinal fold, of which no trace appeared in the cliif of slate above it. 

 Neither was this the only one, for some other crumpled grits showed themselves 

 a little farther south, on the floor of the cove. 



These undulations greatly reduced the thickness, which the appearance of the 

 two grit-bands on the western cliff, dipping steadily south, and so far apart from 

 each other, would have led me at first to assign to the rocks shown in the cove. 

 Nor was this all, for on looking more attentively I found that the two grit-bands, 

 which seemed to strike so steadily towards the east in the western cliff, did not 

 appear in the eastern cliff of the cove at all, but were cut off by some fault or 

 " trouble " at the south-east corner of the cove. 



The western cliff was formed wholly of slate, which might at first sight be 

 supposed to dip south, but did in reality undulate in various directions, and was 

 in some places horizontal. This was shown by the little parallel bands of dark 

 and light-grey colour, about one-tenth of an inch wide, producing what we call 

 " ribboned slate " in Ireland. They were traversed by a well-marked cleavage, 

 which dipped south at 60°, and one set of joints was parallel to this cleavage, pro- 

 ducing exactly the appearance of bedding, so that any observer who was not 

 greatly on his guard, might easily have been deceived, by the facts observable in 

 this cove, into assigning a steady persistent southern dip to the whole of the 

 beds. 



From what I saw elsewhere about Ilfracombe and Mortehoe, I believe that, 

 while there is a real general dip to the south throughout the district, this dip 

 is by no means so prevalent as it appears to be, and that the total thickness 

 is accordingly much less than wovdd be at first supposed. 



In the little cove of Helesborough, about a mile east of Ilfracombe, 

 the slate contained in one place a strong calcareous band, consisting 

 of nodular lumps of white calc-spar, weathering brown, with strings 

 of the same substance ramifying into the grey slates. The dip hero 

 is certainly south-south-west at 35°. 



7. PicJcweJl Down and Mortehoe. — Proceeding from Ilfracombe to 

 the south-west by Bieklescombe and Score (? Scaur), and thence along 

 the lanes towards Pickwell Down, nothing was to be seen, before 

 reaching Crosscombe, but smaU quarries and cuttings in dark-grey 

 slate, apparently without any grit-bands. It would have been 

 quite useless, therefore, to waste the little time at my disposal in 

 attempting to determine the dip of the beds. The cleavage still 

 dipped e-very where to the south at 60° or thereabouts. At Cross- 

 combe, however, I came on a little quarry in thick, coarse, brownish- 

 red sandstone, with slaty partings, some of which were a dirty 

 yellow, and some of a bright-red. " Genuine Old Hed Sandstone " is 

 the note I find in my note-book as to these beds. They dip S. 10° 

 W. at 45°. Prom this quarry, for a mile and a half to the southward, 

 over Pickwell Down, there is no rock exposed in situ, that I could 

 find, except in shallow little quarries that did not go deep enough 

 to show the " lie" of the rock. The fragments in these quarries, 

 the field-walls that had been built from them, and the angular 

 rubble and pieces covering the ploughed fields and stubbles, con- 

 sisted chiefly of yellow and red gritstones of various shades, from 

 light yellow to dark brown, and from light pink to deep claret- 

 colour. Some pieces of purple slate, or of yeUowish-green slate 

 also occurred. 



I walked over the seaward slope of Pickwell Down, hoping to 

 find some natural or artificial excavation that would disclose the 



