1866.] JUKES — OLD RED SANDSTONE AND DEYONIAN. 339 



there to be merely the topmost beds of that formation, and that if 

 the denudation had spared the rocks a httle more, they would still be 

 covered by the Coal-measures. Coming to the west, that limestone 

 is evidently becoming debased and dying away, for in the farthest 

 quarry to the west, while there is one good mass of Crinoidal Lime- 

 stone, the chief part of it is gritty and earthy-looking, and so impure 

 that they have ceased to quarry it for burning into lime. Black shales 

 lie in the ground half a mile farther west, in the lane leading from Old 

 Five Mile Bridge, and on the hill to the north of it, where impres- 

 sions of Posidonomya are abundant. 



If those black shales, and those of Ballyheedy, are really Coal- 

 measures, it will show another analogy with Devon, where the Culm- 

 measures (which are exactly like the Irish Coal-measures) rest on 

 the Carboniferous slate without the possibility of drawing any decided 

 line between the two*. 



The most obvious conclusion, on comparing the sections of Water- 

 ford and Kilkenny with those of Midleton, Ballea, and Ballinhassig 

 (figs. 2 to 8), is doubtless that the Lower Limestone shale has ex- 

 panded to the south-west, independently of any change in the Car- 

 boniferous Limestone, and that the beds which form the base of the 

 Limestone at Ballea are the same beds which are the base of the 

 Limestone at "Waterford, for instance. This, however, is not a ne- 

 cessary conclusion, and I now believe that the limestones die away 

 from below upwards in proportion as the shales or slates be- 

 come thicker ; so that what appear to be the lowest beds of Car- 

 boniferous Limestone in the south-west, are on the same geological 

 horizon as the upper beds of the limestone to the east and north. 



Owing to the want of continuous sections, and the frequent un- 

 dulations of the beds, it is impossible to assign very accurate thick- 

 nesses to the several rock-groups in the Ballinhassig section, fig. 8. 

 Perhaps we might calculate the Ballyheedy Coal-measures at 500 or 

 600 feet thick ; the thickness of exposed Old Bed Sandstone as 1500 

 feet ; and the Carboniferous Slate, between the two, as showing a 

 thickness, which may be as little as 3000 feet, but may be as much 

 as 5000 feet, or more. 



8. Old Head of Kinsale. — The greater estimate is certainly not 

 too great for the thickness of the Carboniferous slate a little farther 

 south, about Kinsale for instance. The narrow promontory which 

 is known as the Old Head of Kinsale stretches out to the south for 

 3 miles, with vertical chfis on each side of it. The beds strike east 

 and west from one cliff to the other, and can be examined on both 

 sides from a boat, and are occasionally accessible on land. Their 

 general dip is north, at angles varying from 40° to 80° or 90°. 



* Mr, Godwin -Austen describes the limestone of Ugbrook Park, near Newton 

 Bushel, in South Devon, as Carboniferous Limestone with Devonian (or Strin- 

 gocepjiahcs Limestone) below it. Although I have not yet been able to visit the 

 locality, I have no doubt of its being accurately described by Mr. Grodwin -Austen, 

 and that the Ugbrook Park Limestone is like that of Ballea, just the uppermost 

 beds of the true Carboniferous Limestone, with the Carboniferous Slate lying 

 under it, enclosing inliers of String ocephalus Limestone, and some of the peculiar 

 forms of fossils to which the name " Devonian " has been assigned. 



