1873.] CAMPBELL GLACIATION OP IRELAND. 211 



7. The Northern Irish Ice-system. — The most conspicuous moraine 

 that I have seen in the British Isles is at a point at the northern 

 horn of Donegal Bay, at a place called Clogher. It is marked hy 

 dots upon the inch-scale Ordnance Map. It is there nearly three 

 inches long, and it consists of at least six parallel ridges of angular 

 stones. The largest of these are as big as small houses ; and they 

 rest where they were tilted off the ice, like stones shot from the end 

 of breakwaters at Plymouth and Holyhead. Above this conspicuous 

 moraine is " Cruach Beg," a hill of puddingstone ("? pebble-beds of 

 the Old Bed) which is glaciated up to the top, 860 feet. The marks 

 run along the top and side of the ridge horizontally, parallel to the 

 moraine, aiming over the sea at the low country about Lough Conn, 

 and at the head of Clew Bay, beyond that low gap. Here is one 

 side of the bed of a glacier as deep as the hill is high ; but the other 

 side was over in Sligo, beyond Donegal Bay*. 



Following Donegal Bay round the coast, and looking to striated 

 rocks, ridges of drift, and all other marks known to me, it seemed 

 clear that the whole area of the bay, and all the lowlands about it, 

 from Barnes Gap and the hills about it round by Lough-Erne side 

 and Ballyshannon, past Sligo to Loch Conn, were covered by a sheet 

 of ice which bore heavily upon a hill-top 860 feet high, at Clogher, 

 near the end of Donegal. 



But the low lands about Lough Conn are glaciated as Sweden is ; 

 and great stones, like those which are in situ about Clogher and 

 Slieve Liag, are scattered about the low lands at which striae point 

 from " Cruach Beg " and Teelin Harbour. 



Clew Bay is like Donegal Bay. The low grounds are all made of 

 long ridges and furrows of drift which point westward, as do glacial 

 striae and other marks down to Achill Head, along the northern 

 coast of the bay. From Barnes Gap, east of Donegal Bay, to the 

 northern horn of Clew Bay, there was continuous ice moving sea- 

 wards, as it appears to me. But that was not the limit of the Irish 

 ice according to its marks. 



Depth. — Vast time has elapsed since the local systems were united. 

 The weather has worn out many tracks, and chiefly those which 

 were highest and oldest. The ice was more than 2000 feet deep at 

 many places ; but it must have been far deeper. In Connemara 

 is Shan Folagh, a ridge of hard quartz standing apart from the rest 

 of the group of mountains, and about 2000 feet high. On this iso- 

 lated top the rock is well glaciated, chiefly from the north-east. 



The Atlantic is on one side ; and the nearest block of ground of 

 equal height in the other direction is in Antrim or in Scotland. Ice 

 must have gone over this hill. I once thought it was drift-ice 

 afloat ; I now think it was part of the ice which covered Ireland from 

 Donegal to Gal way. 



High marks. — Beginning with the smallest class of mountain- 

 glaciers, Irish marks have led back to large river-glaciers, to small and 

 large local systems, to a combination of several local systems in an 

 estuary of glaciers in Donegal Bay, to the union of two estuaries in 



* Rubbings were shown. 



p2 



