1873.] CAMPBELL — GLACIATION OF 1KELAND. 203 



which appear as spots upon the Mountain-Limestone in geological 

 maps. 



After seeing the destruction worked upon Dungannon sandstones, 

 and the denudation of regions about Lough Neagh and Lough Erne, 

 it is also seen that engines able to do such work may have destroyed 

 coal-formations over the whole area of " denuded" Mountain-Lime- 

 stone in Ireland. But if they did, then the low grounds are chiefly 

 hollows made by the same engines which destroyed the Antrim 

 chalk and Sligo limestone. "Weathering and rivers could not and 

 did not do this work, which I attribute to ice and the sea. 



VIII. Valentia. — At the other end of Ireland, at Yalentia, near 

 the telegraph station, is a bank of Boulder-clay scarped by the sea. 

 Slate rocks have there been crushed, smashed, and ground to powder. 

 Chips remain in the clay so arranged as to prove that the engine 

 which here crushed the solid rock came from the mainland down 

 certain deep glens, split on Valentia Island, and went seawards on 

 both sides of the island. 



An instantaneous photograph of withered leaves caught up and 

 whirled along by a strong wind might give some notion of the 

 arrangement of chips of slate in the clay at Valentia. But in the 

 immediate neighbourhood are finely polished, hard, grooved slate 

 rocks, which prove that a great stream of heavy ice passed into 

 Dingle Bay, moving north-westward after it split on Valentia Island 

 and crushed the softer slate. The other half of this stream went to 

 sea westwards. 



IX. Ice and the Sea. — At these three places, about Lough Weagh, 

 Lough Erne, and Valentia, the destruction of rock is recorded, as 

 the quarrying of slate is at Valentia and at Bangor, by remnants left 

 standing in quarries. At these three places marks of glacial action 

 upon a very large scale abound, and extend vertically from the 

 highest tops to the sea-level. But these glacial marks upon the 

 surface commonly end abruptly at the brink of tall cliffs, which the 

 sea is undermining and has undermined. 



Off the south-west coast, far out at sea, tall peaks and scarped 

 rocky fragments, the same in all particulars as rocks in neighbouring 

 points, stacks, rocks, and needles, out to the Skelligs 700 feet high, 

 are monuments of havoc wrought by the sea, after the ice-engine 

 had struck work. Upon these outliers all the power of waves and 

 weather now spend their utmost force ; and the effects are manifest 

 in cliffs at all the exposed points in the south-west. It is easy to 

 see that Irish rocks have been greatly worn from above, and that 

 ice did a great deal of the grinding. It is plain that the sea now is 

 destroying the land by undermining it. The shape of Irish lands 

 and coasts I attributo chiefly to the working of these two engines, 

 ice and the sea. 



X. Glaciation. — Glacial marks can best be seen amongst bare rocky 

 hills, where rock-surfaces are most exposed, and where the shape 

 of glens and hills, which arc grooves and ridges in the solid, can best 

 be distinguished from piles of loose drift. The structure of hills can 



