344 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 7, 



12. Dingle Beds. — Although it has no direct bearing on the subject 

 of this paper, it may still be pointed out that in the promontory north 

 of Dingle Bay, the Old Eed Sandstone diifers somewhat from that 

 just described, both in lithological character and in the thickness and 

 lie of the beds. 



In the Dingle Promontory the Old Eed Sandstone contains much 

 more conglomerate than it does south of Dingle Bay. It has large 

 masses of quartzose conglomerate, and also a very singular local mass 

 containing chiefly angular fragments of granite, gneiss, mica-schist, 

 felstone, and gritstone. This is sometimes as much as 400 feet thick, 

 but thins out rapidly in each direction. AVe have spoken of it as 

 the " Inch Conglomerate " (see Mr. Du Noyer's descriptions in Ex- 

 planation of Sheet 160, &c., pp. 6, 14, and 41). 



This Old Eed Sandstone rises conformably from under the base of 

 the Carboniferous Limestone and has a thickness of 3,000 or 4,000 

 feet, but it rests quite unconformably on some highly inclined red 

 rocks, — slates, sandstones, and conglomerates, — which have a much 

 greater thickness and a rather different lithological character. These 

 seem to repose conformably on Ludlow and Wenlock rocks at Dun- 

 quin and Ferriter's Cove. We have provisionally designated them 

 as the Dingle Beds. They are at least 10,000 feet thick. Their 

 conglomerates differ both from the Inch and the quartzose conglom- 

 erates of the Old Eed Sandstone, their pebbles being chiefly rounded 

 and angular pieces of brown sandstone, in some of which Llandovery 

 fossils were found. The Dingle beds also contain beds of blood-red 

 slates of a brighter colour than any usual in the Old Eed Sandstone 

 of Cork or Kerry. On the other hand, their sandstones and grit- 

 stones are very much the same as those found in the rocks of the 

 Iveragh and Dunkerron Promontory, south of Dingle Bay, especially 

 some pecuhar-looking sandstones lithologically identical with the 

 « Glengariff Grits." 



While, then, I cannot by any means feel sure that some of the 

 lowest rocks seen in the country south of Dingle Bay are not the 

 DINGLE BEDS, it was thought best not to assert that as a fact 

 without further proof, and each district has therefore been coloured 

 in our maps according to its own evidence. In the Dingle Promon- 

 tory the beds on which the Old Eed Sandstone rests unconformably 

 are separated from it as " Dingle Beds." In the maps of the other 

 district the colour used to distinguish the uppermost beds, which are 

 undoubtedly Old Eed Sandstone, is continued over the lower ones 

 because we failed to discover any characters which would enable us 

 to draw a lower boundary to them. 



13. Gradual Changes in Lithological Character. — It must not 

 be forgotten that in thus tracing these continuous masses of rock 

 across such large portions of Ireland there occur gradual lithological 

 changes in them, which might easily mislead an observer who saw 

 them only at distant intervals. Any one who visited only the Old 

 Eed Sandstone of Waterford, and then went at once to Glengariff in 

 Bantry Bay, without examining the intermediate district, might de- 

 cline to believe that the Old Eed Sandstone there was part of the 



