SYMONDS NOTES OF A GEOLOGIST IN IRELAND. 



331 



. amount of contortion and twisting in the rocks of that coast is extreme ; 

 but for the minutiaB of detail, we refer the traveller to the maps and 

 printed papers of the gentlemen attached to the Geological Survey of 

 Ireland. 



In the west of England, the Bala or Caradoc-beds are overlaid by the 

 May Hill or Llandovery rocks, which are really the base of the Upper 

 Silurians, and it is said that a portion of this May Hill Sandstone group 

 underlies the representatives of our Wenlock and Ludlow rocks at 

 Dingle. In Galway, on the shores of Lough Mask, and at Ughool, in 

 the county of Mayo, my friend Dr. Melville informs me that Ireland 

 furnishes, what he considers to be, the exact equivalents of our English 

 May Hill deposits, and their passage upwards into true Wenlock deposits. 

 That the Dingle promontory contains the representatives of the Wenlock 

 and Ludlow rocks, we cannot doubt. The uppermost Silurian beds 

 are overlaid by the Glengariff-grits and Dingle-beds, which are esti- 

 mated by Professor Jukes and Mr. Du !N'oyer at the enormous thickness 

 of 10,000 or 12,000 feet. 



The red slates which cover up conformably the upper Ludlow 

 deposits with Pentamerus Knightii, must be the Irish representative of 

 the English Tilestone group ; and the overlying Glengariff-grits and 

 Dingle slates are, we imagine, the local representatives of our masses 

 of Cornstones and Brownstones, which are so well developed in the 

 Brecon Yan district, and in the cornstones of Herefordshire and Brecon, 

 and which, with the Tilestones, I believe to be rightly denominated 

 by the good old term of Old Red Sandstone." Thus we have in the 

 Dingle rocks, 1. Upper Silurians. 2. Tilestones. 3. Glengariff-grits. 

 4. Dingle-beds. The tilestones are red slates and sandstones, the 

 Glengariff-grits green and purple grits with red and greenish slates, 

 and the Dingle-beds consist of red sandstone and slates with thick beds 

 of conglomerate, which contain' pebbles of Silurian limestone and 

 fragments of hornstone and jasper. 'N'ow, over all these beds are 

 deposited, unconformably, red sandstone and conglomerates, which are, 

 I have no doubt, the representatives and correlatives of our English 

 red sandstone and conglomerates, which overlie our Upper Cornstone 

 series or Brownstones, and are, in some instances, as at Dean Eorest 

 and on the Blorenge, unconformable to the Brownstone below. This 

 so-called Old Red conglomerate" in England and Scotland passes 



upwards conformably into the yellow sandstone and carboniferous shales^ 



2 c 2 



