244 



THE GEOLOGIST. 



sea ; the Eeeks of Macgillicuddy, 3000 feet ; some of the mountains 

 to the west of the iieeks, such as Caher, 3200 feet ; with Brandon 

 Mount, 3121 feet; and Benoskee Mount, 2713 feet — both in the 

 Dingle Promontory ; we must be struck with the singular fact, that 

 up to an elevation of 2400 feet they are all rounded and covered with 

 water-worn blocks, while above that level they are more or less peaked, 

 and their surfaces rugged and bristling with the coarsest angular 

 debris and massive rock-flakes, evidently the result of long-continued 

 atmospheric action; to this there is one exception in Mangerton 

 Mount, which is 2715 feet in elevation, whose summit is completely 

 rounded, — a fact which we may account for by supposing it to be the 

 result of some local depression of this part of the mountain chain 

 during the period of the "Drift" action, or a subsequent upheaval 

 after its cessation. 



From this peculiarity in the outline of the mountains we may 

 suppose that before the last great upheaval, and at the commence- 

 ment of our last or glacial " Drift " period, the land over the South 

 of Ireland lay submerged to the depth of about 2400 feet, — thus 

 forming a group of islands, the highest of which was the Peak 

 of Carrantuohill, — having shoal-water extending from them in the 

 direction of N.E. and S.W., the present longest axis of the moun- 

 tain chains, and deep channels between them, which are now our 

 valleys. Over this sea great masses of ice floated, and carried blocks 

 of rock to the S. and S.E. from what is now the Galway mountains, 

 and possibly other mountain chains, which lay in what is now the 

 Atlantic, and scattered them over the islands. As the land arose 

 gradually from the waters, its shores and shoals frequently arrested 

 the travelling iceberg ; these, on grounding and melting, deposited the 

 blocks attached to them ; or, on being again floated ofl" by tides, 

 currents, and storms, carried with them any rocks which might have 

 become attached to them or have fallen on them from any clifi* at the 

 base of which they had been temporarily arrested in their course to 

 the soutli wards. 



At an elevation of over 2200 feet above the sea, in a remarkable 

 hollow at the northern summit of Mangerton Mount, there now lies 

 the lake called "The Devil's Punch-Bowl;" along its northern side 

 its waters are dammed up by a mound of very coarse subangular 

 detritus of local grits and sandstones, having a height of 2319 feet 

 above the sea, or 119 feet above the level of the lake. On the sum- 

 mit of this well-marked mound there are many large angular perched 



