244 
TRE GEOLOGIST. 
sea ; the Eeeks of Macgillicuddy, 3000 feet ; some of the mountains 
to the west of the Heeks, 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.AV., 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 off by tides, 
currents, and storms, carried with them any rocks which might have 
become attached to them or have fallen on them from any cliff at the 
base of which they had been temporarily arrested in their course to 
the southwards. 
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 
