278 • Proceedings of the Royal Irish A cademy. 



the striae,' appearing even to have climbed the hill-slopes and overridden the 

 hills around the Donaghmore Glen. 



Two distinct sets of mounds and ridges of drift cover- the floor of the 

 Upper Lough Erne depression. The one set runs roughly parallel with the 

 axis of the valley and appears to be true drumlins. 'J'hese are crossed 

 roughly at right angles by a second set which is to be ascribed to the 

 retreat.- Their combination has resulted in the peculiar outline of tlie 

 waters of Upper Lough Erne.' 



As shown by the moraines along the eastern side of the valley, e.g. those 

 east of Lisnaskea and Maguire's I'ridge, the Erne Glacier persisted after the 

 ice had retreated from the Slieve Beagh hills. 



6. The Foyh and Sivillij Glaciers. 



In Inishowen, moraines and marginal drainage phenomena are singularly 

 poorly represented. 



The ever-diminishing thickness of ice caused the emergence of the highest 

 peaks and ridges, e.g. Raghtin More, Slieve Snaght and the range which 

 rises from the western shores of Lough Foyle. These nunataks, with 

 continued melting of the ice, broke up the once continuous ice-sheet into 

 several separate glaciers, the largest being those occupying Loughs Swilly 

 and Eoyle and the Mintiagh and Glentogher valleys. 



The successive positions of the eastern edge of the Eoyle glacier, as it 

 shrank off the foot-hills of the Sperrin Mountains, liave already been described. 

 The position of its varying western margin is fixed by a few " dry " valleys 

 and an occasional morainic mound on the hill-slopes falling to the western 

 shore of Lough Foyle. One of these well-developed marginal channels was 

 observed at The Colonies, about two miles S.-W. of Moville. It falls north, 

 and intakes at about 430 feet, O.D. A second, in aligned sequence with this, 

 and approximately one mile in length, was encountered near Ballyrattan. 



CorresponcUug to slightly later phases of the retreat of the Foyle Glacier 

 are the small channels to be found near Clare Mount (three miles S.-W. of 

 Moville,, while the somewhat doubtful overflow channels to be observed 



has suggesf.ed, may be true drumlins, formed, however, by ice proceeding from the 

 S.-W., and not from the N.-E., as that writer affirmed. The position of the pointed end 

 of these features, remarked upon by Mr. Hallissy, and regarded by him as exceptional, 

 would thus conform to the ordinary rule. 



' For the striae localities, see the one-inch Geological Survey maps of this area 

 (Sheets 45, 46, 57, 58), and the map (PI. IX) accompanying this paper. 



- The angular clebris, noted by Maxwell Close in some of these ridges {op. cit., p. 218), 

 is doubtless of morainic origin. 



3 A siuiilar aspect would be presented were the drumlin and morainic country of 

 Aughnacloy and Tynan to be partially submerged. 



