to the Mineral Structure of the South of Ireland. J 71 



side of the axis at Shrugh, and on the north side at Crooked 

 Bridge on the road from Lismore to Clogheen. In the lower 

 part of this series the quartz-rock and sandstone predominate, 

 but in the upper part the red clayslate is the prevailing rock. 



Descending the hill on the north side towards Clogheen, 

 and on the south towards Lismore, we find the last-mentioned 

 rocks succeeded by alternations of gray sandstone and red 

 clayslate, beyond which we have the limestone series alter- 

 nating in the commencement with dark-gray clayslate. There 

 is much diluvial matter at the base of the declivity on the 

 north side, and in consequence the yellow sandstone with ca- 

 lamites is not visible there; although to the north of Lismore, 

 at Reaf, and in other parts of both valleys, it may be observed 

 associated with the dark-gray slate, which alternates with the 

 lower beds of the carboniferous limestone. 



If we compare the succession of rocks which form the stra- 

 tification of the Knockmildown mountains, as above described, 

 with those that occur at Ballyvoil Head and Gloundolgan, it 

 would appear that the lowest visible rocks of the Knock- 

 mildown range belong to the upper part of the old red sand- 

 stone suite, which will account for the absence of the thick 

 beds of conglomerate which abound in the lower part of the 

 series in the Monavoullagh range, as at Crotty's rock, Gloun- 

 dolgan and Ballyvoil Head. 



In my paper printed in the Journal of the Geological So- 

 ciety of Dublin*, I have entered so fully into my reasons for 

 considering that the limestones of the valleys of the Suire, the 

 Blackwater, the Bride, the Lee, &c., occupy the same geolo- 

 gical position, both by the order of succession of the strata 

 and by fossils, that I do not think it necessary to discuss the 

 subject a second time ; and conceiving that I have shown that 

 the red slates and conglomerates which overlie the conglo- 

 meritic base at Crotty's rock, at Gloundolgan, and at Bally- 

 voil Head, occupy the entire space between the dark-gray 

 transition slate and the carboniferous limestone, I think I have 

 substantiated my case, and shown that the strata situated to the 

 south of the unconformable junction with the transition slate 

 of the county of Waterford, do belong to a newer series, to 

 which, for reasons already given, I have applied the name of 

 old red sandstone in my large geological map, and in the 

 papers referable to it. 1 shall, however, reply to one state- 

 ment of Mr. Weaver's in regard to the stratification of the 

 ridge interposed between the valley of the river Blackwater 

 and the Bride, which, he observes t> "are said by Mr. Grif- 

 fith to partake of a similar composition to that of the northern 



* See vol. ii. part 1. 



t See Lond. and Ed. Phil. Mag. for April, 1840, p. 228. 



