﻿156 Royal Geological Society of Ireland. 



1. The Upper, consisting of massive sandstones, shales, with 

 beds of coal, black-band and clay-band, ironstone, &c. (Lingula 

 squamiformis). 



2. The Middle, consisting of a thin bed of limestone lying 

 between shales, with carboniferous-limestone genera and species 

 of shells, crinoids, and corals. 



3. The Lower, consisting of massive reddish grit and conglo- 

 merate with thin beds of shale. 



The author showed that the Carboniferous Limestone of Ireland 

 undergoes in its extension northwards changes similar to those of the 

 same formation in Britain when traced from Derbyshire into Nor- 

 thumberland and Scotland. The calcareous member thins away and 

 is replaced by sedimentary strata of sandstone and shale, showing 

 approximately terrestrial conditions productive of coal and ironstone. 

 It was thus that in the case of the Glasgow coal-field the limestone 

 of Derbyshire, several thousand feet in thickness, was represented by 

 only thin bands of earthy limestone interstratified with a thick 

 series of grits, shales, &c., with ironstone and coal. In a similar 

 manner the Ballycastle coal-field, with only a few feet of limestone 

 shown in the cliffs of the Bay, was the representative of the Carbo- 

 niferous Limestone of the centre of Ireland, nearly 3000 feet in 

 thickness. 



Mr. Hull considered the lower division (No. 3) of the Ballycastle 

 beds (as above described) to be undoubtedly the representative of the 

 " calciferous sandstone series " of the Geological Survey, which lies 

 at the base of the Carboniferous rocks of the West of Scotland, and 

 that the middle and upper divisions (Nos. 2 and 1) correspond to 

 the Carboniferous Limestone series, or lower coal-field of that country. 



As regards the palseontological evidence, it was in favour of this 

 view as far as it had been studied. Out of thirty-three species ob- 

 served in the limestone band of Ballycastle Bay, 50 per cent, had 

 been described in the Lower Carboniferous rocks of the West of 

 Scotland ; and one of the uppermost seams of coal lying above the 

 limestone had yielded Lingula squamiformis, a form characteristic of 

 the Limestone series in the north of England, Scotland*, and Ireland. 

 Mr. W. H. Baily, F.G.S., concurred in the view of the age of these 

 beds on palseontological grounds. 



The author concluded by pointing out several features of similarity 

 between the Ballycastle beds and the lower coal-series of the West 

 of Scotland, such as the occurrence of several beds of " black-band " 

 ironstone, the hydraulic and earthy character of the limestone of 

 Ballycastle Bay, exactly resembling the " Arden " and " Cowglen " 

 bands of Glasgow. Some uncertainty still remained whether there 

 were any beds in the Ballycastle district as high in the geological 

 series as the millstone-grit, or true coal-measures ; but until more 

 light could be brought to bear on this question by further explora- 

 tion, and a complete investigation by the Government surveyors, the 

 author meanwhile regarded the whole series as Lower Carboniferous. 



* John Young, Trans. Geol. Soc. Glasgow, vol. ii. 



