386 MAJOR A. E. DWERRYHOUSE 0~S THE [vol. lxxix, 



Eelmount Hill (377 feet) southwards across the Draperstown 

 Railway to the neighbourhood of Baveagh. 



The striations on Brackagh Slieve Gallion, on Drumbilly Hill, 

 north-west of Desertmartin, in the area south of Magherafelt, and 

 on the northern shores of Lough Neagh, all indicate a movement 

 of ice in a north-north-easterly direction down the valley of the 

 Lower Bann, and the course of this glacier will now be traced 

 towards the northern sea. Its width extended from the basaltic 

 hills Coolnasillagh Mountain (1340 feet) and Carntogher (1521 

 feet) on the west, over the valley of the Bann at Portglenone 

 and the high ground east of it, into the neighbourhood of Ahoghill 

 and Grace Hill in the valley of the River Main, where it was 

 confluent with Scottish ice from the valleys east and north-east of 

 Ballymena, which it was powerful enough to deflect northwards. 



The western margin of the Bann Glacier, and its deposits in the 

 valley of the Bann will first be considered. The marginal pheno- 

 mena are best seen on the basaltic spurs which project eastwards 

 from the left slope of the valley. 



Whether the ice passed over the summit of Coolnasillagh there 

 is no direct evidence to show ; but, if Ave judge from the direction 

 of the striations, south-south-west to north-north-east, near Sheskin 

 Bridge in Glenshane Pass, this seems highly probable. 



That an ice-lobe penetrated the pass from the south-east is indi- 

 cated by accumulations of gravelly drift and the existence of two 

 overflow-channels, one on the line of the pass at 946 feet, and the 

 other north of Crockcor at an altitude of slightly over 1000 feet. 

 These channels both fall north-westwards, and terminate at about 

 850 feet in Glenshane, at Avhich level there are large spreads of 

 gravel that probably mark the level of a glacier-lake. 



The first of the basaltic spurs mentioned above is that north of 

 the valley cariying the road from Maghera to Glenshane Pass, and 

 between it and the Pullan Water. It is cut through by a number 

 of channels, the most marked of these being at 560, 480, 380, 320, 

 and 280 feet respectively. They all fall northwards, and took the 

 overflow of a lake impounded between the ice and the spur, at 

 successive stages of the retreat. The largest of the channels is 

 that at the 380-foot level, which contains Killelagh Lough. This 

 channel is cut in basalt, is 100 feet wide, and has a flat floor. The 

 lough is on the watershed which is at the southern end of the 

 channel, and small streams flow from both ends of the lough. 



Running parallel to the road from Maghera to Swatragh is a 

 lateral moraine of considerable size, which lies between the road 

 and the end of the spur. 



The next ridge in succession is a spur of Carntogher, and the ice 

 impounded a lake in the valley in which Carntogher House stands, 

 between it and the spur previously mentioned. The valley con- 

 tains much dark brown boulder-clay, in which there are several 

 stream-sections, containing many small boulders of schist, vein- 

 quartz, and basalt, with occasional fragments of flint : this 

 material is all local. The drift extends up the Pullan Water to 



