382 PEOCEEDHirGS OF THE GEOLOGICAL SOCIETY. [JunO 18, 



lowest point of a watershed * anywhere, over any limestone ground, 

 in the south of Ireland. 



Thus far the Carboniferous Limestone is continuous from the 

 great plain between Dublin and Galway, spreading round the hills of 

 Lower Silmian and Old Eed Sandstone rocks, and beneath the hills 

 of Coal-measures. 



On the south side, however, of this limestone vaUey, which 

 stretches from Dingle Bay to Dungarvan, the limestone is entirely 

 cut off, and we meet with one continuous range of Old Eed Sand- 

 stone running from the headlands of Kerry, [near Yalentia, out to 

 Helvick Head, on the south side of Dungarvan Bay. 



All the Carboniferous Limestone to be found south of this long 

 ridge consists of detached outliers, forming vaUeys and low grounds 

 in the long synclinal hollows of the Old Bed Sandstone. These, with 

 their intervening anticlinal ridges, run along lines bearings at first 

 due E. and W., but gradually curving round as we go westwards, so 

 as to iTin E.N.E. and "W.S.W. The intervening ridges of Old Eed 

 Sandstone are of moderate height in "Waterford and the eastern part 

 of Cork, ranging from 400 to about 800 feet above the sea ; while no 

 parts of the limestone valleys rise to more than 200 feet, and their 

 general level is less than 100 feet above the sea. As we proceed 

 westward, however, towards Kerry, the ridges rise higher, and the 

 limestone valleys become narrower and shallower, until the Old Eed 

 Sandstone alone, but bent into similar curves, forms the well-known 

 mountainous district west and south of Killarney, between Dingle 

 and Bantry Bays. 



All the hills, indeed, to the south-west of a line drawn from "Wex- 

 ford Harbour, past Cashel to Limerick, run from east to west ; and 

 most of them rise gently from the east, with their culminating points 

 towards the west. Not only does the present surface of the ground 

 rise higher towards the west, but the beds themselves that form these 

 ridges, while they almost always dip at high angles either to the north 

 or south, nevertheless rise imperceptibly towards the west, so that 

 each bed gradually crops out towards the west, in the bottom of the 

 synclinal or on the crest of the anticlinal folds, those folds being stiU 

 apparent westwards, but in successively lower beds. We may ex- 

 press this structure by saying that the axes of the curves are gently 

 inclined, so as to sink towards the east, or rise towards the west. 



All the large open valleys of this south-western corner of Ireland, 

 too, run E. and W. along the strike of the rocks, having been ex- 

 cavated along the uppermost beds as they dip into the synclinal folds. 

 The lateral, or north and south, valleys are narrow and precipitous, 

 and either shallow and at high levels, or else deserve the name of 

 glens or ravines, rather than that of valleys. 



As far south as the latitude of Cork, the Carboniferous Limestone 

 is separated from the Old Eed Sandstone only by the beds of black 



* Some definite term is wanted to express the lowest point of a watershed be- 

 tween two adjacent basins of drainage, or that point which would first connect 

 them if one or both had their present mouths completely blocked up. Perhaps 

 the phrase, " lowest connecting gap," might be used to express this. 



