Papers Bead at the British Association. 423 



basalts can only be approximately determined. They are newer than 

 the Carboniferous Limestone which they are seen to traverse at 

 Cranfield Point, Carlingford, and elsewhere. EecoUecting the abun- 

 dant evidences of contemporaneous volcanic action which the Car- 

 boniferous rocks of Scotland and the North of England and Stafford- 

 shire present, the authors are disposed to refer these older basalts 

 to the Carboniferous period ; and, having regard to the prodigious 

 number of these dykes traversing the rocks at intervals along the 

 coast from Dundalk Bay to Dundrum Bay, they suggest the former 

 existence of one or more volcanic vents in their vicinity during 

 later Carboniferous times, such as has been inferred to have existed 

 in the vicinity of Carlingford by Dr. Haughton.^ 



Sequence of Granitic, Plutonic, and Volcanic Bocks in the Mburne 

 District. — The following may be regarded as the order of succession 

 of these rocks, with their approximate ages, in the district north of 

 Carlingford Bay, all being more recent than the age of the Caradoc 

 beds of the Silurian epoch ; commencing with the oldest we have — 



(a) Metamorphic Granite of Slieve Croob, Castlewellan and Newry; Fre-Carbon- 



iferous : Fost Silurian. 



(b) Older Basaltic dykes of Mourne and Carlingford; Upper Carboniferous. 



(c) Diorite dykes ; later than the Carboniferous. 



{d) 1. Granite of Mourne, 2. Felstone and Porphyry dykes penetrating the Granite 



of Slieve Croob and the older Basaltic dykes ; Fost Carboniferous, 

 {e) Newer Basalts of Miocene Tertiary Age. 



Judging by the comparative scarceness of the newer Tertiary dykes 

 in the district of Mourne, the authors draw the conclusion — that 

 it may be considered as the southern limit of the region affected by 

 the volcanic outburst of the Miocene Period, which have left such 

 grand monuments of active force over the districts of the north-east 

 of Ireland and extending into the Inner Hebrides ; while, on the 

 other hand, it was the seat of active volcanic energy during an 

 earlier period, which, in all probability, was identical with the later 

 Carboniferous. 



III. — On the Silurian Eooks of the Pentland Hills and 



Lbsmahago. 

 By D. J. Brown. 



THE author showed that in the Pentland Hills both the Wenlock 

 and Ludlow divisions of the Silurian Eocks are represented, 

 and that the Lower Old Eed Sandstone formed no part of these beds. 

 Also, that these Pentland beds are not the equivalent of the Lesma- 

 hago, but that these latter are a higher portion of the Ludlow series 

 than any found in the Pentland Hills. 



I 



IV. — On the Silurian Eocks of the South of Scotland. 

 By D. J. Brown. 

 N this paper the author endeavoured to show that the Silurian 

 rocks of the South of Scotland, as developed in Dumfriesshire 



^ Quart. Joum. Geol. See. vol. xii., p. 193. 



