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



to the south, and the surface of the ground also falls again in that 

 direction, but much more gently. The Old Eed then passes beneath 

 the Lower Limestone shale and Carboniferous limestone of the valley 

 of Dungarvan, as shown in Pig. 5. 



The thickness of this Old Eed Sandstone is, according to Mr. Du 

 Noyer, not less than 1.700 feet near the Suir valley, increasing towards 

 the south-west until it becomes upwards of 3000 feet north of Dungar- 

 van (see Explanation of sheets 167 &c. of the Irish Survey Maps, and 

 the Longitudinal section, sheet 13). The Lower Limestone shale also 

 is materially thicker on the south of the Comeraghs than it is on the 

 north. The black shales and the flaggy limestones near Clonea Castle, 

 about four miles east of Dungarvan, seem, from their exposure on 

 the shore, to have a thickness of 600 or 700 feet. They, however, 

 as well as the limestones immediately above them, are so much 

 affected by slaty cleavage that the bedding is often greatly obscured 

 by it. This fact is observed by Sir H. De la Beche in the ' Memoirs 

 of the Geological Survey,' vol. i. p. 76. 



The gently undulating arch of Old Eed Sandstone which forms the 

 Comeragh Mountains, is continuous as a ridge of lofty ground for 

 thirty-five miles to the westward, first sinking to 650 feet in the 

 pass of Ballynamult, then rising to 2600 feet in the peaked hills 

 called the Knockmeildown Mountains, and then dying away in the 

 much lower Kilworth Hills south of Mitchellstown. The gentle un- 

 dulations in the beds in the Comeraghs become more pronounced 

 farther west, and the beds are folded into sharp anticlinal and sjn- 

 clinal curves, which let in a little trough of shale and limestone in 

 the very centre of the hills between the Knockmeildowns and the 

 Kilworth Hills. 



The axes* of these curves then gradually sink towards the west, 

 and the Old Eed Sandstone dissappears in that direction beneath the 

 plain of Carboniferous Limestone that extends from Mitchellstown to 

 Mallow. The undulations in the beds, however, do not cease, the 

 limestone beneath the plain being bent into curves like the Old 

 Eed Sandstone of the hills. 



This Carboniferous Limestone, after wrapping round the extremi- 

 ties of the Kilworth Hills, runs down the valley of the Blackwater 

 past Lismore and Cappoquin, and is continuous out to Dungarvan 

 Harbour and Clonea. Between Fermoy and Dungarvan the Lime- 

 stone lies in a long narrow trough, the Old Eed Sandstone, which 

 dips underneath it from the hills on the north, quickly rising out 

 again towards the south into a persistent ridge, which stretches east 

 and west right across this part of Ireland from Dungarvan Harbour 

 to Doulus Head in Dingle Bay, a distance of 120 miles. 



5. Old Heel Sandstone of North Corh, South Waterford, and South 

 Kerry. — This continuous ridge forms the northern margin of a tract 

 of Old Eed Sandstone, having a mean length of 100 miles. It is 

 18 miles broad at the eastern end, measuring from a little south of 



* By the axis of a curve I understand the purely imaginary line about which 

 the beds may be suppos?d to be bent, and not any particular mass of rock that 

 appears at the surface. 



