68 Mr. Weaver on the Geological Relations of the South of Ireland. 



the south and that of the Slievenamuck, Slieve Riagh, and Seefin on the north, 

 and upholds on each side mountain masses of old red sandstone (§. 48.), are 

 several quarries of roofing-'slate, covered by a considerable accumulation, con- 

 sisting of clay, in which are imbedded numerous boulders and pebbles of slate, 

 greywacke, sandstone, and limestone, and not a few of greenstone porphyry, 

 red felspar porphyry, and purplish claystone porphyry. The first four enu- 

 merated kinds of rolled debris, have evidently been derived from the fixed 

 rocks of the immediate neighbourhood. But whence have the porphyries 

 been derived? To find analogous rocks in situ we must travel some distance 

 to the north ; where they are to be found in association with the carboniferous 

 limestone of Lough Gur, Kilteely, and Pallis. 



(88.) The last case I shall notice is in the peninsula of Renville, the west- 

 ern extremity of which, is by land about four miles from Oranmore, and by 

 sea about the same distance from the town of Galway. It forms a low tongue, 

 the base of which is carboniferous limestone, but the surface is mostly occu- 

 pied by a considerable deposit of limestone gravel and marl, inclosing 

 numerous boulders and pebbles of red and grey granite, syenite, greenstone, 

 and sandstone. This case corresponds perfectly with the preceding. The 

 limestone gravel may be said to be the produce of the immediate subsoil; but 

 the granite, syenite, and greenstone, if not the sandstone also, must have 

 been drifted from the northern side of the bay of Galway, where they con- 

 stitute an extensive district. 



(89.) These instances may suffice to show, that the evidences of diluvial 

 action are no less conspicuous in the South of Ireland than in the other parts 

 of the world, to which observation has extended. And, from the last two 

 cases mentioned above, it might be inferred, that the general current of 

 the waters was from the N.W. to the S.E. ; a view which, making allowances 

 for eddies produced by intervening obstacles, is in accordance with my remarks 

 on the East of Ireland^ : and I may add also with those of Mr. Bryce in the 

 North, as since ably developed, by that author, in his memoir on diluvial action 

 in the North of Ireland*. 



' Geol. Trans, First Series, vol. v. Memoir on the East of Ireland, Alluvial Tracts, §§. 202 to 

 211, and in particular §§. 209 and 210. 



- Journal of the Geological Society of Dublin, Part I. 



