288 Proceedings of the Royal Irish Academy. 



The small morainic mounds, observed north of the Silver Hill-Binbane 

 range, e.g. in the valley of the Oweuoe Eiver, just S. of Doobin, to tlie S.-E. 

 of Meenagu.shoge Hill, and to the S. of Lough Magrath More, prove that 

 the ice cleaved north and south along the line of this ridge. 



A small terminal moraine of the glacier flowing along the valley of the 

 Owenea Eiver was observed about one mile S. of Glenties. Larger moraines, 

 above and below Martin's Bridge, were deposited by the same glacier at a 

 later stage. These may perhaps be correlated with the moraine at the 

 western end of Lough Finn. 



10. The Great Finn Glacier. 



The retreat from the region now to be described is largely bound up with 

 the recession of the great mass of ice in occupation of the Finn valley, which 

 at an earlier stage spread over the intervening watersheds into the valleys of 

 the Derg and Swilly. It is here comprehensively denoted the " Great Finn 

 Glacier." As moraines are practically absent, the manner of its withdra'wal 

 has been largely determined by the magnificent '• dry valleys " of the area. 



After the emergence of the higher part of the Omagh range and the sepa- 

 ration of the Fintona and Drumquin glaciers, these for some time continued 

 to flow round the eastern shoulders of the range, west of the town of Omagh, 

 and abut against the lower and south-east slopes of MuUaghcarn. Proof 

 of this is furnished by the sweep of the moraines from the east of Omagh 

 northwards along the sides of the hills in the direction of Deer's Leap. 



Further evidence is forthcoming in the occurrence of overflow channels 

 at the south-west foot of MuUaghcarn. The highest of these was observed 

 near Tiri^uin. It intakes just below 500 feet, O.D. A second and slightly 

 later channel intakes near Gornary at an altitude of about 450 feet, O.D., 

 beginning as a shelf on the hill-side. 'J'he small glen, which intakes just 

 below the lasL-mentioned channel and pursues a course down the natural 

 slope, marks a somewhat later position. Yet another " dry " valley was 

 observed at Killybrack. These channels, all cut in " solid " and falling 

 north, show that the ice had retreated from the terrain in that direction. 



The further shrinkage of the ice from this hill-side caused, at a somewhat 

 later stage, the complete severance of the glaciers streaming to the north 

 and south of the Omagh range and the development of an ice- free area about 

 Omagh. 



The retreat of the ice-lobe south of the range — the "Fintona Glacier " — 

 was sketched in an earlier section. The wide glacier of Lrumquin, north 

 of the range, extended down the valley of the Strule in the direction of 



