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



The felsites of the whole of Kilf arrasy Strand belong not improbably 

 to the same late period. 



Such are the principal groups of felsitic rocks, but we have also to 

 notice the more isolated and differentiated occurrences, and must 

 make an attempt to fix their relative ages. Thus the beautiful 

 columnar sheet of pink felsite of Kilfarrasy Island is obviously still 

 later than the felsites which it pierces, and these themselves belong 

 to the latest group above mentioned. Perhaps the tongue of purplish 

 felsite in Lady's Cove, Illaunacoltia, is of the same age as this colum- 

 nar sheet. The felsite-porphyry at the western end of Garrarus 

 Strand is also probably one of the later intrusions (see p. 676). 



Morageeha and Knockane Strands. — We may now proceed 

 to notice the felsitic rocks west of Annestown. The group of felsites 

 at the eastern end of Morageeha Strand comprises various types, but 

 they are all associated with a crushed greyish felsite and tuff filling 

 an old pipe. They send out irregular tongues and protrusions into 

 the surrounding rocks, and enclose portions of the black slates 

 which bound them on the west. These black slates, which dip 

 generally north-westward at high angles and are excessively 

 cleaved, were penetrated by several irregular sheets or dykes of 

 felsite subsequent to their crumpling and cleavage. The large 

 detached rock called the Long Rock, near "Knockane Strand, consists 

 of a massive grey felsite which is also exposed in the cliffs behind; 

 and the shattered condition of the neighbouring slates shows that 

 it has burst through them. A large mass of grey quartz-porphyry 

 is here inserted in the midst of this grey felsite, though its re- 

 lations are not seen with distinctness owing to landslips ; but it 

 seems to represent the central plug in the pipe up which the grey 

 felsite welled. The latter is seen to enclose large blocks of the 

 black slate on its western boundary, and the massive sheets of 

 similar felsite that occur on the adjoining promontory separating 

 Knockane from Morageeha Strand, and show similar relations to the 

 black slates, are probably apophyses of it. There is a small vent 

 situated just here, consisting of a plug of grey felsite, of the same 

 type as that of the Long Eock, surrounded by a zone of brecciated 

 slate measuring in places as much as 12 feet in width. This mass 

 of closely-packed fragments of slate has suffered a rude sort of 

 cleavage with the surrounding slates, in consequence of movements 

 subsequent to the explosion which blew out the vent and filled the 

 pipe with breccia ; but since the felsite itself shows no sign of 

 crushing, these movements must have occurred prior to its injection 

 into the pipe. 



Immediately west of this occurs a sharply-defined and nearly 

 vertical dyke of dark-grey felsite, with regular parallel walls and of a 

 different petrological type, traversing the slates. Two more masses 

 of felsite considerably shattered are found between this spot and 

 Dunabrattin Head, on the western side of which occurs the large 

 boss of horny grey felsite intruded into the base of the Tramore 

 Limestones and previously figured. 1 



1 Quart. Journ. Geol. Soc. vol. lv (1899) p. 736, fig. 14. 



