Chaklesworth— Glacial Geology of North- West of Ireland. 289 



Newtownstewart,resfcing on the eastern flanks of Bessy Bell and on Deer's Leap, 

 at one stage depositing a moraine spanning the valley. Most probably 

 corresponding with this position of the ice-front is the overflow valley, falling 

 north, observed east of the hill of Deer's Leap. Larger morainic belts mark 

 the successive halts in the retreat from the hills to the east of this valley. 

 The finest is that which is crowned by the Mountjoy Forest and which is 

 partially responsible for the sontheiiy course taken by the Fairy Water. 

 It sweeps northwards under the village of Mountjoy and on to the southern 

 slopes of Bessy Bell. 



A similar series of moraines was noted along the foot of the northern 

 flanks of the Omagh range to the east and west of Drumqnin.' At one 

 stage a lake was impounded in the embayment south-east of Drumquin ; its 

 surplus waters escaped by tlie valley followed by the Omagh- Drumquin road. 



To the west of Drumquin the glacier appears to have split into two, one 

 branch receding towards the head of the large recess drained by the 

 Blackwater, the other, the major glacier, keeping to the broad depression 

 of the Fairy Water. A series of recessional moraines flung across the 

 Blackwater valley marks the retreat of the smaller glacier. One of these has 

 so obliterated the old course of the river that the stream now escapes across 

 the barrier by falls and a gorge cut in the " solid " rock at the Carrickaness 

 Bridge. 



As a result of the emergence of Bessy Bell from the surrounding ice and 

 the cleavage in the ice to the north-east of this hill, the lobe withdrawing 

 southwards along the Strule valley towards Mountjoy became separated from 

 the glacier occupying the valley of the Derg. This glacier had at the same 

 time parted from the main Finn Glacier somewhere on the line of the 

 present watershed between the valleys of the Finn and Derg. The broad 

 and ahnost streamless valley east of Eaws Hill possibly drained a shallow 

 glacial lake located on the site of the present Moneygal Bog and held up 

 between the glaciers filling the Finn and Derg depressions. The position of 

 the northern edge of the latter glacier is given by the huge Fyfin-Victoria 

 Bridge overflow valley,- which intakes N.-E. of Fyfin Station at an altitude 

 of just below 300 feet, O.D. 



The position of the ice-front at this stage of the retreat is further indicated 

 by the pronouncedly morainic belt skirting the southern foot of Olady Hill. 

 This broad strip of very hummocky country, studded with small pools and 

 forming a most conspicuous feature in the landscape, runs as a series of ridges 



'These are the "drift hillocks of irregular shapes" of the Geological Survey 

 Memoir (Sheet 33, p. 19). 



^ The Castle Derg and Victoria Bridge Tramway skirt-s the northern side of the valley 

 over the stretch from Fyfin Station to Victoria Bridge. 



