158 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



That some at least of tlio vents along the south coast of County 

 "VVatcrford may be vastly younger than the Lower-Silurian rocks 

 through which they have forced their way is suggested, if not 

 proved, by a section which is in some respects the most extraordinary 

 of the whole of this remarkable series. The occurrence of a group 

 of red strata was carefully noted by the late Mr. Du Noyer at 

 Ballydouane Bay, when he was engaged in carrying on the Geo- 

 logical Survey of that part of the country. At first he regarded 

 them as belonging to the Old Red Sandstone, which comes on in 

 great force only a few miles to the west ; but he subsequently 

 arrived at the belief that they are really an integral part of the 

 Lower-Silurian rocks of the district. Professor Jukes expressed him- 

 self in favour of this latter idea, which was thought to receive 

 support from the occurrence of some reddish strata in the Lower- 

 Silurian rocks of Tagoat, County Wexford *. 



The occurrence of red rocks among Silurian strata, which are 

 not usually red, might quite reasonably be looked for in the 

 neighbourhood of Old Eed Sandstone, Permian, or Triassic 

 deposits. If these deposits once spread over the Silurian formations, 

 a more or less decided *' raddling " of the latter may have taken 

 place. But in the present instance, though the Old Red Sand- 

 stone begins not many miles to the west, no such explanation of 

 the colour of the strata is possible. The cliffs of Ballydouane Bay 

 consist of red sandstone, red sandy shale, and conglomerate. The 

 red tint is of that dull chocolate tone so characteristic of the Lower 

 Old Red Sandstone. The conglomerates are immense accumulations 

 of ancient shingle, consisting largel)' of pieces of white vein-quartz 

 and quartzite, sometimes a foot long and often well water-worn. 

 Some of the sandy beds are full of large scales of white mica, as if 

 derived from some granitic or schistose region at no great distance. 

 Taken as a whole, the strata are much less indurated and broken 

 than the Silurian grits and shales of the district ; some of them, 

 indeed, weather into mere incoherent sand that crumbles under the 

 fingers. There does not appear to be any positive proof that the 

 red rocks are truly bedded with the ordinary Silurian strata, the 

 junctions being faulted or obscured by intrusive igneous masses. 



Nowhere in tlie British Islands, so far as I am aware, is there a 

 similar group of strata among the Lower-Silurian rocks. If they 

 belong to so ancient a seiies, thej^ show that in the south of Ireland, 

 during Lower-Silurian time, there arose a set of peculiar physical 



* Explanation of Sheets 167, 168, 178, and 179 of the Geological Survey of 

 Ireland (1865), p. 10. 



