ANNIVERSAUr ADDRESS OP THE PRESIDENT. 7 1 



counties of Lanark, Ayr, and Dumfries, traversed by the Duneaton 

 Water, a fifth volcanic area may be traced. Its boundaries, how- 

 ever, are indeterminable, as it is overspread with Carboniferous 

 rocks both to the north-east and south-west. It possesses consider- 

 able interest, inasmuch as it exhibits, better perhaps than any other 

 of the volcanic areas, the alternation of volcanic discharges with the 

 continuous accumulation of the ordinary sand and gravel of the 

 lake. In its near neighbourhood also lies one of the granite bosses 

 to which I shall afterwards refer in connexion with the vents of 

 ' Lake Caledonia.' 



6th. The remaining portion of the Old Red Sandstone area on the 

 mainlan(f of Scotland from the valley of the Nith to the Firth of 

 Clyde has been so broken up by faults, and so much of it is over- 

 spread with Carboniferous rocks, that some uncertainty must remain 

 as to the distribution of its volcanoes. There were probably several 

 centres of activity. One of these was possibly situated near ^ew 

 Cumnock, and from it may have come the lavas and tuffs of 

 Corsincone on the one side, and those of the hills ranging towards 

 DalmeUington on the other. Another vent, or rather group of vents, 

 lay among the hills to the right and left of the Girvan Valley, south 

 of the village of Straiten. A third rose some miles to the north- 

 east, near Maybole, and poured out the lavas of the Carrick Hills, of 

 which such instructive coast-sections are exposed from Turnberry 

 Point to the Heads of Ayr. But for my present purpose it will 

 suffice to class these different vents together as the Ayrshire group. 



7th. At the extreme south of Cantire another display of volcanic 

 rocks of Lower Old Eed Sandstone age may be studied. Beds of 

 andesitic lavas with tuffs and massive conglomerates overlie the 

 schists of that region, and are themselves unconformably covered by 

 the volcanic series of Lower Carboniferous age, to be afterwards 

 described. 



8th. We have now to cross to Ireland, where a continuation of 

 the same volcanic types may be traced. On the Antrim coast at 

 Cushendall the coarse conglomerates are in main part made up of the 

 fragments of a remarkable quartz-porphyry, which is exposed on 

 the shore at that locality.^ Though there is no proof that this 

 igneous rock has been directly connected with any volcanic discharge, 

 it may be paralleled with such bosses as Tinto, which supplied 

 materials for some of the overlying conglomerates. Farther to the 

 south-west, however, in the county of Tyrone, abundant porphyrite 

 1 See Explanation to Sheet 14, Geol. Surv. Ireland, p. 2o. 



/2! 



