210 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 22, 



Here and there ridges of Boulder-clay and other kinds of drift aim 

 northwards ; and all the loose stones in these hills of drift seemed to 

 be granite of the country. At Dungloe is a considerable ridge of 

 granitic boulder-clay, parallel to the course of the river and to the 

 fjord. "Where the sea has newly washed this clay from the rock, 

 glacial surfaces are perfect *. 



The marks aim from the foot of Slieve Snaght, at the north end 

 of Arran Island. Followed in that direction tbe marks still aim out 

 to sea northwards and to the west of north. Prom rising grounds 

 near the sea, Arrigle and Mookish are seen above the granite lowlands. 

 At the base of the high cone of Arrigle are great blocks of grey 

 granite resting upon the quartz ; and all along the sky-line seen from 

 Glen Veagh and from the Gweebarra Pass great stones are perched. 



The solid granite is in tbe S.E. ridge of Glen Veagh, quartz is on 

 the N.W. side of that furrow ; and the granite boulders seem to have 

 crossed from the Slieve Snaght ridge towards the N.W. 



All recent glacial marks that I could find in this region indicate 

 a local system of Donegal glaciers which moved as ice now moves 

 about Bergen and in Iceland. In particular tbe ridge which divides 

 Glen Veagh from Gweebarra Pass was covered by a sheet of ice like 

 Lang Jokull in Iceland, which flowed off it as water flows off the 

 roof of a house into gutters. The ice, according to its marks, once 

 was about 2000 feet thick, and went out to sea ; but it dwindled and 

 shrank till nothing remained but river-glaciers, and then mouutain- 

 glaciers of the smallest size, with one of which I began. (XII. 1.) 



6. Irish local systems. — That which is true of Donegal is true of 

 all the groups of mountains which I have visited in Ireland. 



A smaller local system left conspicuous marks on the peninsula 

 which ends in Slieve Liag, wbich I have already mentioned (XL). 

 Another was in the Antrim mountains. There moraines are en- 

 tirely made of fragments of rocks of Antrim. Whole walls are built 

 of boulders of basalt ; and the Boulder-clay is brown. Glacial 

 marks upon the rocks follow the run of water, beside rivers, from 

 the snow-shed downwards. Prom Lame to Ballyeastle the Antrim 

 glens were filled with glaciers like those of Donegal, which were like 

 those of Iceland. Another large local system was in the Mourne 

 Mountains. Another had the Twelve Pins and other hills of Conne- 

 mara for gathering-ground and starting-point. 



Another was in the group of hills on the west side of Lough Neagh ; 

 another was in the Sligo hills ; another was out near Achill Head. 



A very large system was in the south-western corner of Ireland, 

 with the high grounds about Killarney for gathering-ground and 

 the sea for receptacle. This last has been described by Mr. Close, 

 and by other writers. 



Knowing something of all these systems, and of others of less size, 

 it is proved, by marks about which there can be no doubt, that Irish 

 glaciers, down to latitude 51°, were equal in area and dimensions to 

 the largest local ice- systems in Iceland, which touches the Arctic 

 circle. But the Irish ice-system was still larger at an earlier time. 

 * Specimens of glaciated granite were shown. 



