TBANSACTIONS OF SECTION C. 541 



TUESDAY, AUGUST 20, 1878. 



The following Papers were read : — 



1. On the Influence of "Strike " on the Physical Features of Ireland. 

 By Edward T. Hardman, F.G.S.,F.E.G.S.I, Geological Survey of Ireland. 



Although not often mentioned in geological works, the influence of " strike " in 

 determining the lines of direction of the principal physical features of a country is 

 recognised by most geologists, but in few countries is the relation so distinctly 

 shown as in Ireland. The author was led to pay attention to this subject on 

 reading Mr. J. F. Campbell's paper ' On the Glaciation of Ireland,' * in which that 

 gentleman assumes that the south-west and north-east trend of some of the 

 mountains of Ireland is due to the glacial action of a huge ice sheet passing over 

 Ireland from the south-west of Scotland. After some years' examination, how- 

 ever, the author has found that in most cases the trend of the hills, and course of 

 rivers, &c, are determined by the strike alone ; and he now wished to place the 

 facts noted before the section : — 



(1) Mountains. — The Donegal highlands trend to the south-west, along the line 

 of strike of the ancient crystalline stratified rock. The basaltic plateau of Antrim 

 follows in outline the windings of the outcrop of the underlying chalk, and, conse- 

 quently, the strike of the basalt upheaved with it. The Mourne Mountains and 

 Slieve Croob also coincide in direction with the stratified rocks on their flanks, 

 except where joints or faults have given rise to minor lateral valleys, e.g. Car- 

 linsrford Lou«h. Adherence to the line of strike is also seen in the hills forming 

 the flanks of the Wicklow Mountains, in the Kilkenny and Tipperary coal-fields, 

 the Comerao-h and Knockmealdown Mountains, and is most remarkably shown in 

 that series of flexured carboniferous, old red sandstone, and Silurian rocks forming 

 the hills of Cork and mountains of Kerry, the axes of which stretch from Dun- 

 garvan (Co. Waterford) to Cape Clear and Ban try Bay. Its influence is again 

 shown in the shaping of the high ground forming the Munster coal-field, and 

 finally in the mountainous district of Connemara ; although here, in places, 

 obscured by the action of faults. The Twelve Pins, Muilrea, the mountains 

 flankino- Killarney harbour, and the country northwards around Nephin Mountain 

 are striking examples. Towards the central plain the isolated mountains of old 

 red sandstone and Silurian rocks rising through the carboniferous limestone, viz., 

 the Slieve Bloom Mountains, the Devil's Bit, and the Galtees, conform to the same 

 rule, the axis in strike and direction being parallel. 



(2) Rivers. In the North of Ireland especially, many of the rivers follow the 



windings of the strike. The Suir follows the line of strike for eighty miles, only 

 beginning to cross it about ten miles from the sea. The Blackwater runs along the 

 strike for seventy miles of its course, crossing it for only sixteen miles. The Lee is 

 directed by the strike for some fifty miles of its length, as is also the Bandon 

 River for the greater part of its course, while tbe Shannon may be traced along the 

 strike of the beds for by far its greatest distance. 



(3) Inland Lakes. — Most of the lakes are conformable to the strike in their 

 o-reater outline, tbe smaller details being determined by the jointing. Of these may 

 be mentioned Lough Neagh. Loughs Corrib and Mask, Lough Erne (most notably), 

 Lou"h Allen, Lough Derg, and the far-famed Lakes of Killarney. 



(4) Sea Loughs, Bays, 8,-c— Tbe majority of these may be included :— Lough 

 Foyle, Belfast Lough, Strangford Lough, Lough Larne. The most notable ex- 

 ample's are those in the south-west :— Roaring Water Bay, Dunmanus Harbour, 



* ' Quart. Journ. Geol. Soc.,' Londou, May 1872. 



