On the east side of Slieve Gallion at the head of a narrow glen called Tintugb Glen, about 1300 feet above the level of the sea, crop out several unconnected masses of greenstone.
They are totally unconnected with the flat stratified trap which overlies the chalk, and crowns the summit of the mountain. The fissures are lined with calcareous spar, and veins of crystallized heavy spar and of red compact iron stone are contained in this rock.
D. Old Red Sandstone.
This formation has been observed only in the two following districts, and even there its extent appeared to be very limited.
1. In the county of Down, on the sides of Strangford lough.
2. On the N.E. coast of Antrim, between the bays of Cushendall and Cushendon; and again in Murloch bay.
Vestiges indicative of the old sandstone may also be traced along part of the shore of the Isle of Rathlin opposite Fairhead.
The tract of sandstone first specified extends from the E.N.E. side of Strangford Iough to Scabro hill on the opposite side of that lough, appearing likewise at Ballymasca, Dunlady, and Kirkdonnel.
Scabro hill rises 483 feet above Strangford lough, its summit is composed of a cap of greenstone about 150 feet in thickness; the remaining 330 consist principally of the sandstone, which may be observed in one[1] of the quarries opened on that hill (to procure this material for architectural purposes) in distinct beds of very variable thickness alternating with greywacke.
- ↑ The name of this quarry it the White quarry.
