CoLte—On the Geology of Sheve Gallion, in the County of Londonderry. 215 
on the opposite flank. The northern end is still capped by an outher of almost 
horizontal basalt, preserving a thin layer of chalk, and repeating the features of 
the Antrim plateaux. Hence it is unlikely that the summits were ever peak-like 
or serrated, at any rate since the time that they formed part of the floor of the 
Cretaceous sea. The cirques at the head of the great combes have now become 
choked and grass-grown; and both flanks of the range are covered by huge fan- 
like taluses. The great days of Slieve Gallion, however, must have been when it 
rose as a promontory in the Carboniferous ocean, a buttress of the contorted 
district to the north and west. The Carboniferous sandstones that rest against the 
mountain are largely composed of its products of decay*; and denudation is now- 
a-days, as in the Wicklow mountains, restoring to us, on a somewhat reduced scale, 
the scenery of Paleozoic shores. At the north end of the mountain, the mantle of 
Carboniferous sandstone has not yet been stripped away, and the rocks are 
conspicuous by their stratification and their warm red-brown colour. 
Gerard Boate,t in 1755, referred to the possibility of mineral wealth in ‘ the 
mountains Slew-galen”’; and an iron-mine was then being worked in the Lissan 
valley. His suggestion that ‘rich gold mines do lye hidden”’ in Sheve Gallion 
seems still to exercise a fascination over the peasantry, who believe their highland, 
from Carncose to Oritor, to be capable of great mineral development. Nor are 
they discouraged by the failure of various attempts at iron-working,§ but regard 
all geologists who visit them as speculators in gold or coal. 
G. V. Sampson’s map,|| which was issued by the Dublin Society in 1802, 
records the occurrence of granite on Slieve Gallion, and of basalt and ‘‘ white 
lime” on the northern summit. His mineralogical and geological notes show 
characteristic powers of observation. 
Jean Frangois Berger{ carefully examined the mountain in 1816, especially 
noting the granitic series and its variations. 
Sir R. Griffith,** in 1829, showed an acquaintance with the problems of the 
district; and the changes made in successive editions of his famous Geological 
* Geol. Surv. Mem. sheet 27, p. 16, &e. 
} The upper part of these sandstones, on the steep scarp of Slieve Gallion North, was regarded by 
Portlock as Triassic (‘‘ Report on Geol. of Londonderry,” p. 114; also G. H. Kinahan, ‘Geology of 
Ireland,” p. 141). Mr. Egan, howeyer, with much probability, has referred them to the reddened Lower 
Carboniferous series (Geol. Survey Mem. sheet 27, p. 18). 
{ “A Natural History of Ireland,” Pt. i., pp. 69 and 71. 
§ See G. V. Sampson, ‘‘ A Memoir explanatory of the Chart and Survey of the County of London-Derry, 
Ireland” (1814), p, 97. Also Geol. Surv. Mem. sheet 27, p. 42. 
|| ‘Statistical Survey of the County of Londonderry, drawn up for the Dublin Society.” 
q ‘‘ On the Geological Features of the North-eastern Counties of Ireland.” ‘Trans. Geol. Soc. London, 
vol. iii., p. 144, &e. 
** «¢ Geological and Mining Surveys of the Coal Districts of the Counties of Tyrone and Antrim,” p. 1. 
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