1862.] JITKES — ^EIVEE-VAILETS. 381 



from the county Cork, through Kerry and Limerick, into Clare. It 

 is cut in two by the broad estuary of the Lower Shannon. Towards 

 the northern part of Clare, a thin coating only of Coal-measures is 

 is left on the high land, which is there formed of the Carboniferous 

 Limestone, — hills of hmestone, more than 1000 feet in height, form- 

 ing the Barony of Burren, and looking down upon Galway Bay. 



These limestone and Coal-measure hills are separated from the 

 Slieve Aughta and Slieve Bemagh by a low limestone tract, spreading 

 from Galway, past Gort and Ennis, to the Lower Shannon, the water- 

 shed of which is in the neighbourhood of Gort, and is in some places 

 not higher than 150 feet above the sea. It is a branch of this low 

 limestone country which runs out to Lough Derg by Scariff, between 

 the Slieve Aughta and Slieve Bernagh hills. 



The part of the limestone plain lying on the east side of Lough 

 Derg forms a similar country, and sends a branch down the Kilma- 

 stullagh valley, between the Slieve Arra and the Keeper group, to the 

 Shannon at O'Brien's Bridge, and another smaller one through the 

 Gap of Eoscrea, between the Devil's Bit range and the Slieve Bloom. 



This latter branch, which thus connects the limestone plains on 

 each side of the central ridge of Slieve Bloom, is traversed by the 

 main watershed of Ireland at a level not higher in some places than 

 360 feet above the sea. This part of the main watershed runs be- 

 tween the basin of the Shannon and that of the Nore. 



To the south of the hills just described the limestone country again 

 expands into a plain, in parts of Limerick and Tipperary, between the, 

 extension of the two Coal-measure high lands, embracing, however, 

 several minor east and west ranges of lower rocks. The watershed 

 on this plain, between the basin of the Shannon and that of the Suir 

 River, is not higher in some parts, near the Limerick Junction Rail- 

 way-station, than 330 feet above the sea. 



The most important of the east and west ranges that rise here- 

 abouts is that of the Galty Mountains (3015 feet) and their sub- 

 ordinate groups. These are surrounded by branches of the limestone 

 plain, which meet about Castletown Roche, and conduct us into the 

 valley of the Blackwater. The watershed between the basins of the 

 Suir and Blackwater, in the western branch, is about Castle Harrison,, 

 near CharleviUe, at a height of about 374 feet ; that in the eastern 

 branch is about the Caves of MitcheUstown, and is about 400 feet 

 above the sea. 



The valley of the Blackwater Eiver again enables us to cross 

 Ireland whoUy on the Carboniferous Limestone, in a nearly straight 

 line from sea to sea, starting from Dungarvan Harbour, and ascending 

 the Blackwater, past Cappoquin, Lismore, Permoy, Mallow, and Mill- 

 street, and then descending into the basin of the Flesk, and continuing 

 out by KiQamey and Killorglin into Castlemaine Harbour in Dingle 

 Bay. Between Millstreet and Killamey, however, the limestone is. 

 entirely concealed for some nules by great accumulations of drift, pro- 

 bably not less than 200 feet in thickness ; and the watershed between 

 the Blackwater and the Flesk basins rises in consequence to a height 

 of 550 feet at the lowest point. This is the greatest height for the 



