Eeports and Proceedings. 181 



west of Ireland, tracing the Old Eed Sandstone and Carboniferous 

 Limestone from Wexford through Waterford into Cork, and show- 

 ing that some thin beds of black shale, which intervened between 

 those groups on the east, expanded westward until they acquired a 

 thickness of two or three thousand feet. The group then received 

 Sir E. I. G-riflath's appellation of Carboniferous Slate. The Old Eed 

 Sandstone similarly expanded to the west, from a thickness of a few 

 hundred feet in Wexford to one of several thousand feet in North 

 Cork. Slaty cleavage, which shows itself in both these groups on 

 the east, becomes more marked on the west, until they might both 

 be spoken of as clay-slate formations. 



West of Cork Harbour the Carboniferous Slate is covered in one 

 or two places by patches of black slate, which Mr. Jukes believes 

 to be the lower part of the Irish Coal-measures, resting conformably 

 on the Carboniferous Slate, with no very definite boundary between 

 the two, as in North Devon. He believes, accordingly, that as the 

 Carboniferous Slate expands towards the west, the Limestone dies 

 away from below upwards, and that the beds which are the base of 

 the Limestone at Ballea, a few miles west of Cork Harbour, are on 

 the same horizon as the Upper Limestone beds of Waterford, even 

 these uppermost beds disappearing a little further west. He, there- 

 fore, looks on the Carboniferous Slate, especially in its upper part, 

 as being contemporaneous with the Carboniferous Limestone. He 

 believes that there is a regular consecutive series from the Old Eed 

 Sandstone into the Coal-measures, through the carboniferous Lime- 

 stone in one area, and through the Carboniferous Slate in the other. 



In North Devon the author considered the dark slates and sand- 

 stones, which strike from Baggy Point and Croyde Bay by Marwood 

 and Barnstaple to Dulverton, identical with parts of the Carboni- 

 ferous Slate of Ireland ; and red and variegated sandstones and slates, 

 rising out to the northward from underneath the grey series, identi- 

 cal in character with the Irish Old Eed Sandstone. On a recent 

 visit, however, to the north coast at Lynton, Ilfracombe, and Morte- 

 hoe, he found that those beds also were identical in character with 

 parts of the Carboniferous Slate, and contained some of the same 

 fossils as are found in Ireland and in the Barnstaple district, each 

 district having fossils not found in the others. 



These beds, in the absence of any reason to suspect the contrary, 

 would be judged to pass under the Old Eed Sandstone. Eelying, 

 however, on the conclusions formed in Ireland, Mr. Jukes believes 

 that the central band of Old Eed Sandstone must be cut off towards 

 the north by a great longitudinal fault, with a downthrow to the 

 north of some 4000 feet. Mr. Jukes pointed out that this hypo- 

 thesis would do away with the necessity of asssigning the enormous 

 thickness to the North Devon rocks which the ordinary hypothesis 

 requires. 



After discussing in general terms the objections that may be 

 urged against the hypothesis, especially the palgeontological ones, 

 he ventured to propose that geologists should no longer include the 

 Old Eed Sandstone among the Devonian beds, but confine the term 



