70 G. H. Kinahan — The Silurian Rocks of Ireland. 



merates are usually small, and of white quartz, with some of red 

 jasper) ; but south-west of the valley of the Suir, in the Commeragh, 

 Galtee, and Knockmeeldown ranges, the type changes, the rocks 

 being massive purplish conglomerates, interstratified with slaty grits 

 or gritty slates. The pebbles in these conglomerates are often very 

 large, while the maximum thickness of the subdivision seems to be 

 considerable. The upper portion of the subdivision (called Upper 

 Old Bed Sandstone on the Geological Survey Maps, and Yellow 

 Sandstone by Griffith), however, is still very like the Central Ireland 

 type, except that the conglomerates are few or altogether absent. 

 North of the Galtees, in Slieve Phelim, Kimalta, Slieve Arra, Slieve 

 Bernagh, and Slieve Aughta (counties Tipperary, Limerick, Clare, 

 and Galway), the rocks are for the most part of the Central Ireland 

 type, although in places there are massive conglomerates ; while 

 in Slieve Bloom (King's and Queen's counties), the rocks are more 

 like the Commeragh type. 



South of the valley, between Dungarvan and Dingle Bay, there is 

 a very complete change in all the rocks ; from the base of the Coal- 

 measures downwards, they assume peculiar types. The Cork type 

 of the Old Red Sandstone has below massive, although generally 

 cleaved, purplish and dark grey grits and slates (Old Bed Sandstone) ; 

 and above, when typical, yellow and greenish grits and shales, 

 over variagated green, red, liver-coloured, and rarely purple slates 

 (Upper Old B,ed or Yellow Sandstone). 



The Old Bed Sandstone is very constant in its characters, but the 

 Yellow Sandstone changes considerably in the east and west direction, 

 To the eastward, where it is overlaid by the Lower Limestone Shale 

 and limestones, the Yellow Sandstone partakes in part of the Central 

 Ireland Type, and contains more or less red beds ; but towards the 

 westward, where it is overlaid by the Carboniferous Slate, the red 

 rocks die out, and the sandstones are replaced by grits. The greatest 

 and most sudden change that I have observed is in the neighbourhood 

 of the bay called Kenmare Biver. On the north and south sides of 

 this bay, in the neighbourhoods of Sneem and Ardgroom, are tracts 

 of Carboniferous Slate lying on Yellow Sandstone. Those to the 

 eastward are cut off by faults with downthrows to the west, and 

 further east, at Kenmare, are limestones and the Lower Limestone 

 Shale resting on bright red rocks, the latter lying conformably on 

 the Old Bed Sandstone. These bright red rocks are evidently on 

 the same geological horizon as the Yellow Sandstone to the westward 

 of them, although so totally different. The Old Bed Sandstone 

 extends conformably downwards into the Glengariff Grits, which, as 

 previously stated, are considered both by Griffith and Jukes to be the 

 equivalents of the Dingle Beds, and by the first to belong to the 

 Silurian formation. 



On the north of Dingle Bay the Old Bed Sandstone belonging to 

 the Carboniferous is nearly similar to that in Cork, but in places it 

 contains conglomerates. It has a great thickness (over 5000 feet), 

 and its upper portion is somewhat like the Yellow Sandstone of Cork, 

 but contains more red beds. Farther east, in the county Limerick, 



