part 3] GLAClATIOiJ OF NORTH-EASTERN IRELAND. 375 



The surface of the deposit is hummocky and moraine-like in 

 contour, but this is probably due to the erosion of the sands by the 

 powerful springs which arise in many places, and cut deep irregular 

 valleys. The. sands are usually stratified, and contain many beds 

 of laminated clay, which in some cases (as at Stranmillis) is used 

 for the manufacture of bricks. 



Coarse sands and gravels of the ordinary fiuvio-glacial type occur 

 higher up the valley in the neighbourhood of Lisburn. These are 

 well exposed in gravel-pits west of that town ; and in one of these 

 excavated in a mound near Causeway End, the following erratics 

 occur : — basalt, Triassic sandstone, flint, chalk, reddish quartz- 

 porphyry, Carboniferous sandstone with veins of calcite, black 

 limestone, syenite, vein-quartz, dolerite, glauconitic chalk, Tardree 

 rhyolite, mica-schist, Silurian grit, quartzite, red granite (Tyrone), 

 gneiss, fossil wood from the Lough-Neagh Clays, greenish-grey 

 gabbro, Ailsa Craig eurite, and fragments of marine shells. 



The sands are red, and obviously contain much Triassic material ; 

 and nearly all the erratics have come from the north. The pebbles 

 of rhyolite from Tardree travelled across the Templepatrick area, 

 and along the strip of country between Lough Neagh and the 

 Belfast Hills, by way of Stone} r ford. 



Farther west, in the neighbourhood of Moira and Soldierstown, 

 erratics from Tyrone are very common ; and this country lies 

 within the area invaded by the western ice at a late stage of the 

 glaciation. 



The Tyrone erratics include epidiorite, hornblende- syenite, Car- 

 boniferous Limestone, coarse hornblende-diorite, white quartzite, 

 and red quartz-porplvyry, all of which can be matched from rocks 

 occurring in the country north-west of a line drawn from 

 Magherafelt to Six Mile Cross in County Tyrone. 



V. The Area between Slieve Gallion (Tyrone) 

 and the Belfast Valley. 



This is the basin of Lough Neagh, and is bounded on the 

 west by Slieve Gallion (1735 feet; see map, fig. 5, p. 376), which 

 consists of granitoid rocks, crystalline schists, and Carboniferous 

 sediments, surmounted by an outlier of Chalk, capped with 

 Tertiary basalt ; and by the high land south-west of it running 

 by Fir Mountain (1193 feet), Oughtmore (1261 feet), through 

 Pomeroy and Slievemore (1037 feet) to Slieve Beagh (1221 feet) ; 

 finally, on the east by the basaltic Belfast Hills. 



This area was first invaded by the Firth-of- Clyde glacier, as is 

 proved by the occurrence of Ailsa Craig eurite in the drift deposits 

 at the mouth of the Blackwater, at the extreme south-western 

 corner of Lough Neagh. at Armagh, and at Monaghan. The pebbles 

 of Ailsa Craig eurite are mingled in the deposits with many rocks 

 from the Slieve Gallion axis, indicating that they are reman ies 

 from the deposits of the earlier glaciation, and have been incor- 

 porated with the proceeds of the later extensive glaciation from 

 the west. 



Q. J. G. S. No. 315. 2 d 



