part 3] THE GLACIATION OF NORTH-EASTERN IRELAND. 385 



the chain of the Sperrins and the elevated edge of the basalt- 

 plateau into the valley of the Roe and the Lough Foyle depression, 

 and an investigation of these seemed to promise a solution of the 

 problem. 



Prof. Charlesworth had informed me that there was an over- 

 flow-channel at a height of 870 feet, leading over from the head of 

 Glenelly into the headwaters of the Glengomna Water, a tributary 

 of the Moyola ; I subseqtiently found that the col between Crock- 

 brack (1735 feet) and Craigbane was cut by a dry gap falling 

 north-eastwards at a level of 1250 feet, and that the drift-deposits 

 extend up to the 1250-foot contour-line on the sides of Craigbane. 



There are two roads leading over the col between Mullaghmore 

 (1825 feet) and Spelhoagh (1875 feet), the western one into the 

 valley of the Finglen River, and the eastern by Barony Bridge 

 (1176 feet) to Dungiven. The col is thickly covered with brownish 

 sandy drift, containing masses of Carboniferous conglomerate, 

 schist, and vein-quartz, all of local origin. 



At a height of 1000 feet on the south side of the pass, the 

 Altallack River cuts through a great moraine ; and at about 1150 

 feet above O.D., between Barony Bridge and Labbybeige Bridge, is 

 another moraine, which consists of material derived from the south 

 and south-west. 



These facts indicate that the ice stood sufficiently high to over- 

 ride the col between the heads of the Altallack and Altnaheglish 

 Rivers. This col is also cut by an enormous overflow-channel 

 which falls north-westwards, and is streamless. There are, more- 

 over, great morainic accumulations on the western road near 

 Glenedra Lodge, at a height of about 1100 feet. 



On the southern face of the spur of Spelhoagh, connecting that 

 mountain with Craigagh Hill, is a large corrie with precipitous 

 cliffs, the summit of which stands at about 1500 feet above 

 Ordnance datum. These cliffs are cut by two large dry gaps, 

 which are continued by very broad dry channels down the northern 

 slope of the spur into the valley of the Glenedra Water. 



It is thus evident that the ice at one period stood against the 

 southern flanks of Oughtmore and Spelhoagh at a level of at least 

 1500 feet ; and, as this would give an ample force to account for 

 the phenomena which I had observed in other parts of the country, 

 and as I was now within Prof. Charlesworth's territory, I did not 

 pursue these investigations any farther. 



As has already been stated, Slieve Gallion was completely over- 

 ridden at the maximum extension of the ice ; but at a later stage 

 it was a nunatak dividing the ice of The Six Towns Glacier from 

 that of the Moneymore Valley. Both these streams were moving 

 northwards, and they became confluent at the northern end of 

 Slieve Gallion, where enormous masses of morainic material, form- 

 ing a triangle with its apex towards the north, were accumulated. 

 This morainic material rests upon a tough red boulder-ckvy con- 

 taining rocks from the Slieve Gallion area, and extends from 



