Vol. 56.] IGNEOUS EOCKS OF COUNTY WATEEFOED. 693 



Society in 1891. But more recent observation had led him to 

 modify the opinions there expressed. The ground is now under 

 revision by Mr. J. 11. Kilroe, of the Irish branch of the Geological 

 Survey, with whom the speaker had the advantage of revisiting a 

 number of the sections last summer. Mr. Kilroe's work showed 

 that the masses of so-called ' agglomerate ' along the coast were 

 not really such, but in every case which he had examined were 

 intrusive felsites or other eruptive material, crowded with an almost 

 incredible number of fragments of black shale and various igneous 

 rocks. The matrix was not fragmental, but consisted of lava- 

 form material, sometimes showing good flow-structure. Sir Archi- 

 bald had been unable to detect any true bedded lavas in any 

 part of the coast-section which he had re-examined, nor could 

 either Mr. Kilroe or himself find any satisfactory evidence that 

 the tuffs, here and there visible, were connected with the Lower 

 Silurian strata. So far as they could see, the eruptive rocks were 

 all intrusive, and belonged (as the Author had said, and as the 

 speaker had formerly suggested) to some period intermediate between 

 the Bala Group and the Upper Old Red Sandstone. They might 

 not improbably be referable to that great epoch of igneous activity 

 which witnessed the intrusion of so much granite in Scotland and 

 Ireland, and in which the copious volcanic discharges took place 

 which gave forth the materials that now form the Pentland, Ochil, 

 and Sidlaw Hills, the heights of Lome, and various intercalated 

 lavas and tuffs in the Lower Old Eed Sandstone of the north and 

 south-west of Ireland. He thought it quite possible that the tuffs 

 of the Waterf ord coast really belonged to the same period of volcanic 

 activity ; but this was a question on which he hoped that Mr. Kilroe' s 

 further field-work would throw light. He was glad that the 

 Author had taken up the study of the petrography of the igneous 

 rocks of this region, and had produced a paper which would much 

 assist the labours of students of this singularly interesting but 

 very complicated piece of geological structure. 



The Peesident and Prof. Sollas also spoke. 



The Authoe, in reply, said that the abundance of xenolithic felsites 

 and the comparative rarity of true fragmental rocks had been 

 especially noted by him. The foreign fragments in these felsites 

 measured in some cases a yard or more in length, and were 

 often extremely numerous. As to the presence of true bedding 

 in the series of felsitic rocks, he admitted that it was in many 

 instances hard to detect, but in a few cases it seemed sufficiently 

 distinct. The intrusive and imbedded felsites were, however, much 

 more developed than the bedded felsites. True agglomerates were 

 present in the later necks. The date of some of the intrusions 

 probably coincided with that of the granitic masses in the East of 

 Ireland. 



