286 Proceedings of the Royal Irish Academy. 



melting front step by step backwards np the soutbeni and eastern slopes of 

 the valley until it drew completely behind the crest of the hills forming the 

 western side of the Shallogan valley. As tlie ice-front fell back behind the 

 watershed, streams flowing from the melting ice ci;t steadily southward 

 through the crest-line, and produced a few overflow channels discharging a 

 series of small lakelets formed along the ice-margin. One or two failed to 

 cut through the watershed, e.g., that to the east of Denkbeg Hill, which 

 simply carried off the water from the melting ice, and makes only a slight 

 breach in the watershed. Some water escaped by the Carbat Gap. 



A large glacier lingered in the Shallogan valley. It deposited a terminal 

 moraine soulh-east of Denkbeg Hill and lateral moraines along its southern 

 side, though these are probably built upon " tails " from the Knockrawer and 

 ScuUoge mountains. The finest of these moraines in the Shallogan valley 

 forms a conspicuous feature at the south-west or iipper end of Lough Finn,' 

 stretching as a linear hillock across the valley from the foot of Sculloge to 

 the base of the Ourreen Hill. A later terminal moraine occurs on the 

 northern shore of the lake opposite Crockannaragoun. 



A morainic mound occurs at the eastern end of Lough Muck, south of 

 Scraigs. It is in part the cause of the existence of the lake, though glacial 

 erosion is doubtless the primary cause. 



9. Eetreat from the Glengcsh Plateau and the Country North of Donegal Bay. 



On the Glengesh Plateau no moraines were noted and but few overflow 

 valleys. These, of different value, suggest a progressive recession eastward 

 towards the great rampart of hills bounding the plateau in this direction. 



A lake of considerable size was held up in the valley running south from 

 Lougheraherk, and drained by a valley falling towards Kiltyfanned Lough. 

 Some water from the ice-edge farther south would appear to have discharged 

 over ihe col between Croaghnaleaba and Croaghloughdivna and some into 

 the valley leading to Malin More. The overflow at the head of the Owenwee 

 River took the surplus waters of a small lake held up to the north of 

 Stravally, while the valley of tli'e Meentashesk acted as a gutter carrying 

 off the waters from the ice-front. Finally contracting to a glacier in the 

 valley of the Glen Eiver, the ice brushed passed the south-east shoulder of 

 Slieve League, forming a drift feature, in part possibly a '■ tail," in part a 



' It originally impounded a lake on its western side, ivhich was subsequently drained 

 by the stream which has cut through the barrier. Tlie site of the lake is now occupied by 

 a large alluvial flat. 



Most of the mounds and ridges in this valley, west of Lough Finn, are apparently 

 residual or denudation features. 



