328 Geological Society. 



various theoretical questions suggested by a comparative study of 

 the whole of the Scottish Mesozoic strata. 



January 22, 1873.— His Grace the Duke of Argyll, K.T., F.K.S., 

 President, in the Chair. 



The following communication was read : — 



" On the Glaciation of Ireland." By J. F. Campbell, Esq., F.G.S, 



The author stated that almost the whole of the surface of Ireland 

 consists of glaciated rocks less or more weathered, or well preserved. 

 The polished surfaces are covered in low grounds with drift. Boulder- 

 clay, unstratified, is next to the rock ; sands and gravels and peat 

 bogs are above the clay. The solid rocks have been greatly worn 

 away since the formation of the Antrim basalt ; the drift since the 

 Glacial period. The hills and hollows in the rocks are the result of 

 wearing and "denudation;" the debris is the "drift" partially 

 rearranged. 



This was shown by examples in : — 1 st, chalk and basalt in Antrim ; 

 2ud, mountain-limestone &c. in Sligo ; 3, older rocks about Yalentia 

 and the south- west ; 4, granites and metamorphic rocks in Donegal 

 and the north-east. The effect of the Atlantic on cliffs at Slieve 

 Liag in Donegal, and elsewhere on the Irish coast, was noticed. 



It was shown from these large coast-sections that the upper surface 

 now has no relation to the older contortion, fracture, and folding of 

 these disturbed and faulted rocks, which, lie under newer and less- 

 crumpled beds, up to the peat. The probable dimensions of the ice- 

 engines which worked on the surface of Ireland was shown by com- 

 parison of glaciers in Iceland, Norway, and elsewhere, with the Irish 

 marks, which indicate ice of equal size. Beginning with the smallest 

 and rising to larger systems, Irish marks indicate ice of equal 

 dimensions, till horizontal grooves at 2000 feet above the sea indicate 

 ice more than 2000 feet thick, moving over Ireland into the Atlantic 

 in a south-westerly direction. It was shown that the ice at its max- 

 imum probably extended from the Polar Basin to Cape Clear. In 

 support of this view, boulders on Fairhead, and the denudation and 

 glaciation of the central Highlands of Scotland, and of Scandinavia, 

 Finland, and the United States, were shortly noticed. The question 

 whether these extensive tracks were made by glaciers or by ice- 

 bergs was discussed. The marks in Ireland and Scotland seem to the 

 writer to indicate ice more than 2000 feet thick moving along the 

 bottom of lochs, straits, and shallow seas, in water less than 1800 

 feet deep, with large local ice-systems upon high lands. It was 

 shown that glacier-ice aground in water is easier to push horizontally, 

 and so to drive over impediments, in proportion to the weight lifted 

 vertically by flotation. 



Kubbiugs from glaciated rocks placed beside shaded Ordnance 

 maps of parts of Scotland and England, showed that similar forms 

 had been somehow produced on scales of inches and miles upon the 

 rock-surface of Scotland. 



The author's conclusion is as follows : — 



" Ireland has been greatly denuded. Glacial and marine action 



