part 3] GLACIATION OF NORTH-EASTERN IRELAND. 361 



slopes of Carnanniore and Carneighaneigh at levels of about 1000 

 and 900 feet respectively, and a lobe penetrated the Glenmakeeran 

 valley, covered the flanks of Crockaneel and Oghtbristacree to a 

 height of between 700 and 800 feet, and filled Glenshesk up to 

 the great Coskemnacally moraine. The lake in the valley of the 

 Corratavey Burn, which was still receiving the waters from the 

 Loughaveema Channel, overflowed by a deep (now peat-filled) 

 .channel between Carneighaneigh and Crockaneel, and thence along 

 the edge of the ice, cutting the channel at 700 feet between the 

 Owencam River and the Greenan Water, also that at a slightly 

 lower level joining the valley of the latter stream with Glen- 

 shesk, and finally those above the village of Breen on the flank 

 of Bohilbreaga. 



The Breen channels form one of the most striking groups in the 

 North of Ireland. There are three main channels and several 

 smaller ones, all falling westwards, and eventually opening into the 

 great Inver channel. The two largest of the Breen Channels are 

 each about half a mile long, and from a study of the whole group 

 .on the ground it is possible to demonstrate the retreat of the ice 

 stage by stage, indeed almost foot by foot. 



A further retreat diverted the overflow of the Corratavey Lake 

 to the northern face of Carneighaneigh, and two parallel channels 

 were cut immediately above the site of the Glenmakeeran Shooting 

 Lodge at 850 and 800 feet respectively ; a channel also was opened 

 from the headwaters of the Glenmakeeran River, at this stage 

 occupied by a lake, through a col at a height of 689 feet (present 

 level of the surface of peat). This channel flowed in a south- 

 westerly direction, cut across the valley of the Owencam River, 

 which stream it permanently captured, the old V-shaped channel 

 leading over into Killuca Burn being still visible at a height of 

 SO feet above the present level of the Owencam River, at the point 

 where it enters the gorge of the overflow (see fig. 2, p. 362). The 

 gorge is cut in the schists and, at its lower end, in red boulder-clay 

 containing northern erratics. 



This Owencam channel opened into the valley of the Greenan 

 Water, then an arm of the Glenshesk Lake, which at this stage 

 stood at a level of slightly over 400 feet, and overflowed by the 

 Inver channel, which it continued to do until finally drained by 

 the removal of the ice from its lower end. 



A further retreat rendered the Corratavey and Glenmakeeran 

 lakes confluent round the northern end of Carneiganeigh, and 

 allowed their waters to overflow the col (600 feet) at the head of 

 what is now known as Altiffirnan Glen (see PL XXIV). This glen 

 is an enormous dry gorge, excavated in hard schists to a depth 

 of more than 100 feet. It winds considerably, and, at present, S o 

 ■small is the amount of drainage that an artificial channel 1 foot 

 wide is sufficient to carry it off ; even this is dry in summer. 



At its lower end, where it enters Glenshesk, it divides into two 

 portions, and of these the southern branch is the older, Avhile the 

 northern (which is also the larger and deeper) at present carries the 



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