part 3] GLACIATION OF NORTH-EASTERN IRELAND. 411 



flow under Ballymakellet Bridge have cut deeply into, and in some 

 places through, the drift. The stream which rises south-east of 

 the summit of Carnavaddy and flows on the west of Slievestucan 

 exposes sections in stratified gravelly drift at least 40 feet thick, 

 at an altitude of 900 feet. A rough terrace of drift can also be 

 traced round the shoulder of Slievestucan to the valley of the stream 

 which, rising near the source of that last mentioned, passes round 

 the east side of Slievestucan, between that hill and The Castle, 

 and is known in various parts of its course as Shrufawnasheskon 

 and Altboy. In this latter stream, extending between the 700- 

 -and 900-foot contours, is a drift-section upwards of 100 feet in 

 height, forming a great scaur above the stream, and called 

 Spelleekboy. This drift is roughly stratified, and extends up 

 the hillside bej^ond the level of the terrace on the shoulder of 

 The Castle to a height of about 1200 feet. 



Both the streams above mentioned cut into the drift in many 

 parts of their courses, from the 700-foot level to the bridge at 

 Ballymakellet ; and the sections revealed indicate the existence of 

 several parallel lateral moraines, with intervening flats of stratified 

 drift. These deposits were formed in the waters of a lake held up 

 between the margin of the ice and the hillside. 



At the period of maximum glaciation the mountains were wholly 

 covered; but, as the ice-level decreased, the lake took various 

 forms at various levels, and the history of these changes can be 

 worked out by a study of the fine series of dry channels on the 

 spur of The Round Mountain. 



The highest of these is east of The Castle at a level of 

 1100 feet, and discharges direct into Glenmore below the Clough- 

 more moraine. The channel is small and ill-defined, and was 

 formed by the drainage from the glacier before the ice had dwindled 

 sufficiently to allow of the production of a lake. 



A similar origin may be postulated for the channel at about the 

 same level, on the western slope of The Castle. 



The first of the lake overflows is at 950 feet, cuts through the 

 south-western spur of The Castle, and falls southwards. It is 

 broad and shallow but well marked, and is partly occupied by a 

 swamp called Money boy. The second of this series is at 

 900 feet : it is similar to the last-mentioned, which it eventually 

 joins, and produces a deepening of the lower portion. 



This is followed by a small channel at about 810 feet which must 

 have been of a very temporary nature, being early rendered inactive 

 by the opening of the col between The Round Mountain and the 

 spur of The Castle.- 



East of The Round Mountain, and cutting the col last mentioned 

 at about 720 feet, is a group of deep overflow-channels cut in hard 

 dolerite. They unite to form a dark gloomy gorge known as The 

 Cellar, which opens into the Jenkinstown valley. The waters of 

 this channel drained eventually by way of the great Mullaghattin 

 channel into Glenmore (see p. 412). The head of the main 

 ^channel of the group is occupied by a swamp called Loughlyboy, 



