206 Frof. Suit — The Volcanic Sistory of Ireland. 



part a triclinic felspar, in which are inclosed crystals of augite, 

 olivine, and magnetite, together with chlorite, which must be con- 

 sidered of secondary origin. While such is the character of the 

 generality of these Lower Carboniferous lavas, there are occasional 

 variations ; and in the case of the rock of Knockdirk we find a 

 highly silicated felstone forming apparently one of the old necks 

 of eruption. 



Another interesting A'olcanic district referable to this period lies 

 at the entrance to Bantry Bay, amongst the rocks extending from 

 Black Ball Head to Bear Island. They consist of slates, grits, and 

 calcareous bands belonging to the " Carboniferous Slate " and 

 •' Yellow Sandstone " series of Sir E. Griffith. The volcanic rocks 

 associated with these consist of contemporaneous and intrusive 

 felstones, greenstones, with beds of ash, breccia, and agglomerate, 

 and are ably described by Messrs. Kinahan and O'Kelly in the 

 Memoirs of the Geological Survey.'^ Amongst these certain actual 

 vents of eruption are recognized by the authors referred to ; and 

 owing to the variety of volcanic phenomena here exposed in the 

 fine coast-sections, — the beds of felstone, porphyry, ashes, and 

 breccias ; the old volcanic necks filled sometimes with trap, some- 

 times with fragmental materials ; and the dykes which range both 

 through the igneous and sedimentary rocks, — this district offers most 

 instructive materials to the student of the volcanic phenomena of 

 Paleozoic times. 



As the upper portion of the Carboniferous Slate series, which 

 expands into such unusual proportions towards the south-west of 

 Ireland, may, with some probability, be considered as partly the 

 representative in time of the Carboniferous Limestone, it seems 

 highly probable that the submarine volcanos of the south-west coast 

 just described were in active operation at the same period as the 

 earlier ones of the Limerick Basin, and these again contemporane- 

 ously with those of the centre of Scotland and the north of England; 

 so that this portion of the bed of the ocean — swarming as it was 

 with coralline, radiate, and molluscan life — was at this period 

 frequently invaded by sheets of augitio lava poured forth from 

 submarine vents; and by showers of ashes, stones, and bombs, shot 

 forth and strewn by the currents of the sea. 



With these events the history of the Palceozoic volcanic irruptions 

 of our island closes ; and we have to ascend through a long lapse 

 of geological time, including the whole of the Mesozoic epoch, 

 before we again meet with evidence of contemporaneous volcanic 

 action in Ireland. 



Tertiary Period. — After the volcanic fires had slumbered through- 

 out so many ages, they again burst forth in the Tertiary period with 

 unwonted intensity over the area now occupied by the N. E. of 

 Ireland, extending thence to the west of Scotland and the Inner 

 Hebrides. In our own island the area now occupied by these 



1 Geol. Survey Map, Sheet 198, with "Explanations" to Sheets 197 and 198 

 (1860). Also Mr. Kinahan on "The Igneous Ilocks of Berehaven," Joui-n. Geol. 

 Soc. Dublin, vol. vii. 



