252 Proceedings of the Royal Irish Academy. 



composite origin, for the ice-front at this phase stood just clear of its mouth 

 and almost on the western edge of its delta. 



The Dergbrongh moraine and the ice towering above it served as the 

 western end of this combined lake, which extended up the Glenelly some 

 12 miles, and had a depth on the site of Plumb Bridge of about 300 feet. 

 With this lake that in tlie deep Grlashygolgan valley (west of Crockaelady), 

 was at this stage confluent. 



The relief of this country, as will be gathered from the maps, is such as to 

 secure a stable position of discharge during a considerable oscillation and retreat 

 of the ice-front, ensuring persistent cutting along the line of the Inver Burn. 

 Altaravan Glen (A.) and Glengiuk (G-.) were successively in operation while 

 the Iiiver channel was in action, as is proved by the heights of their deltas. 

 A small retreat in the Cullion recess would in turn free the G-lengink and 

 Killymore cols, while in the recess to the north, a \ery extended withdrawal, 

 to be measured in miles, would not affect the drainage along the Inver 

 channel. 



On the floor of the embayment, W. of Plumb Bridge, was laid down a 

 series of moraines. Their invariable convexity to the east is proof of a tlirust 

 in that direction. They are in places' especially conspicuous, and are seen to 

 consist of schist pebbles with much sand, clearly deposited at the foot of the 

 receding ice-front. One exceptionally well-defined position of the ice-edge is 

 given by the morainic mounds running along the northern slopes of the hill 

 east of j\Ioyle Ho., to the south of Killymore Bridge, and by the hummocky 

 and billowy strip of country sweeping along the floor of the amphitheatre 

 from north of this last locality to Agnaglarig. These moraines indicate the 

 thrusting of a large lobe into this huge amphitheatre, resting on the walls on 

 either side of its wide entrance. Between these morainic mounds and ridges 

 the whole floor of the great recess is deeply filled with lacustrine sands and 

 gravels. These are finely displayed in the banks of the Glenelly Eiver,- and 

 represent the floor deposits of " Lake Gortin-Glenelly." 



A small lake, " Lake Douglas," was held up in the upper part of the 

 valley of the Douglas Burn, east of Victoria Bridge. Its waters escaped by 

 a small channel, intaking at about 630 feet, O.D., and falling south. A shelf 

 falling slightly north occurs at Meenawaddy. Its height is about 530 feet, 

 O.D. A later stage is represented by the valley west of Meenawaddy, which 

 intakes at about 470 feet, O.D. 



' E.g., at Shannony Bridge, Carnargan and FuUagherin Bridge. 



2 E.g., at North and South Lislea. The finest of all these magnificent sections is in 

 the banks of this river at the first "e" of Glenelly iiiver" (one-inch O.S. map). Here 

 the section, some 60 feet high, is composed almost entiiely of beautifully stratified sands 

 and well-wom gravel and shingle. 



