Neighbourhood ofKillarney and Dublin. 445 



The old red sandstojie and its conglomerate^ which varies 

 but little in its lithological character, and is found in great 

 thickness incumbent upon the edges of those Cambrian rocks 

 which I compared and identified with a well-known type 

 seen between Bangor and Ogwen in North Wales, and 



Compact arenaceous rocks, varying in character from grey 

 granular quartz to fine clay slate, of great thickness, occu- 

 pying a wide extent of country, and in geological position 

 agreeing with the upper part of the Devonian series described 

 by Professor Sedgwick and Mr. Murchison as rising" from 

 beneath the culm or coal measures. 



The scarcity of fossils and calcareous bands remains a dif- 

 ficulty in comparing the subdivisions with those of Devonshire, 

 but even in the WavelHte of the Ringabella slates, and the fossil 

 remains of Cove and Ballinhassig, we catch at points of re- 

 semblance which may serve as useful guides. These will be 

 dwelt upon subsequently in detailed memoirs. 



Between these latter and the mountain limestone there occur 

 occasionally a few alternations of shales and sandstones of 

 very variable thickness, but appearing to me never to exceed 

 100 feet, and containing the fossils of the true mountain lime- 

 stone, and none others. These beds are what Mr. Griffith calls 

 his " yellow sandstone " formation. Now I must differ from 

 him, and think that they really mark nothing but the gradual 

 transition from circumstances involving a purely arenaceous 

 deposit, to those in which the calcareous matter originated ; 

 and that they are not more worthy of distinct notice in a geo- 

 logical map than would be any of those grits which form part 

 of the carboniferous limestone formation of Yorkshire. 



These sandy beds may be seen in their greatest develop- 

 ment at Goat Island, near Youghal, as first described by Mr. 

 Robert Ball, and are also visible on the coast of Dublin, at 

 Portrane, Skerries, &c. I think I may mention the junction 

 between the upper Devonian rocks and mountain limestone 

 on the river Roughty, in the county of Cork, as one among 

 many localities where they do not exist as laid down upon the 

 map. 



One section will explain the view I take of the whole south- 

 ern series. (PI. I. f. 1.) 



In the gap of Dunloe, near Killarney, at the base of the 

 Purple Mountain, the Cambrian conglomerates support 

 unconformably a thickness of old red sandstone, which 

 probably exceeds 500 feet. This occupies the summits of 

 Tomies and Glena mountains, and at Glena dips rapidly to 

 the south ; here the transition is very sudden into a great 

 thickness of black and brownish slates observable about Lady 



