692 ME. F. E. COWPEE EEED ON THE [NOV. I9OO, 



to Garrarus. Probably to this same outburst belong the xenolithic 

 felsites and greenish tuffs exposed between Kilfarrasy and Annes^ 

 town. It is somewhat doubtful whether these were poured out 

 before the folding of the Ordovician beds, as the mutual relations of 

 the rocks are not very clear, but the felsites and tuffs frequently 

 show stratification and folding, and their strike when traced inland 

 agrees with that of the previous series ; so that the available 

 evidence points to their formation prior to the post-Ordovician 

 folding. 



Some of the irregular masses of felsite-porphyry appear to have 

 been intruded prior to the injection of the smaller intrusive veins 

 which pierce them and the above-mentioned rocks, but were formed 

 subsequent to the folding. 



The small veins, which are of several penological types and inter- 

 mediate composition, mark the next stage of igneous activity, but 

 show slight differences of age among themselves. 



Next comes the intrusion of the basic sills, diabases, etc., and 

 this was accompanied by the formation of a few doleritic dykes 

 and veins. 



Subsequently the igneous intrusions again assumed an acid 

 character, and the felsitic masses of Newtown Head, Passage; of 

 the centre of Garrarus Strand, and of Knockmahon were extruded. 

 Probably at this time too were formed the isolated necks, filled with 

 brecciated fragments of the earlier rocks, which have been described. 



The formation of the felspar-porphyry dykes may now have taken 

 place, but perhaps they are of still later age. Some of them may be 

 connected with the intrusion of the Wicklow granites. The numerous 

 isolated felsitic sheets and veins which pierce the folded rocks, 

 especially west of Kilfarrasy, probably belong to this late period, 

 but their relations to the other igneous rocks, except where some of 

 the latter are exposed with them, is generally doubtful ; and the 

 most that can be asserted is that they are later than the folding. 



The relative age of some of the peculiar types of intrusive rocks 

 has been previously indicated, but in other cases there is no means 

 available by which we can determine it. 



V. Conclusion. 



By the aid of the facts recorded in the foregoing pages, it has 

 been shown that there are two main periods of volcanic activity 

 exhibited in this area : the first, Ordovician ; the second, post- 

 Ordovician, but pre-Upper Old Ped Sandstone. Next, that the 

 second period is characterized by a succession of several distinct 

 types of igneous rocks ; while the first period is marked solely by 

 outpourings of a felsitic nature. 



Discussion. 



Sir Aechibalu Geikte stated that he had examined this in- 

 teresting region several years ago, and had given some account 

 of its igneous rocks in his Presidential Address to the Geological 



