Charleswueth — Glacial Geology of North-West of Ireland. 249 



Fore G-len tovvaixls the north-east. All the streams coming into the lake from 

 the south threw down their detritus to form the huge shingle and sand 

 terraces which lie at, roughly, 400 feet above sea-level, and fringe the 

 southern shores.' 'J'hey ha\e in places a slightly billowy surface, occasional 

 lakes marking the more pronounced hollows, e.g. Tullintrain Loncrh. 



Like the present Longh I)erg, this extra-glacial lake had two outlets 

 both in operation simultaneously. They drained into the Eiver Eoe. The 

 one extends as a deep and extremely broad valley (F.O.) from "The Glen" to 

 the south of the village of Teeny. The intake is about 430 feet, O.D. At 

 Altcattan Bridge, just south of Teeny, the overflow proper begins, where 

 . the valley has cut deej^ly into the " solid." The present small stream is out 

 of all proportion to the huge valley in which it flows. 



The second outlet is the Ballymouey overflow (B.O.), at the head of the 

 Fore Glen, the intake of which is likewise about 430 feet, O.D. Like the 

 Feeny overflow, it is wide and flat in its upper portion, which also was a 

 transition from lake to outflowing river. 



At an early stage in the exca^■ation of these gorges, wlien the level of the 

 lake was somewhat higher, the waters of the two branches, in the Fore Glen 

 and in the Feeny area, then probably cut off from each other by ice standing 

 to the east of Claudy, were doubtless confluent along the broad flat valley ^ 

 (altitude about 450 feet, O.D.) west of Mullaghmeash Hill. A lake in the large 

 valley of the Burutollet, which at a later stage was confluent with " Lake 

 Claudy," was at this period independent of it, the ice standing across the valley 

 somewhere on the line of the present Ifess "Waterfall, or slightly east of this 

 locality. The well- developed gravel mounds of Barr Gregg most probably 

 mark its position at some stage. The discontinuous morainic ridge near 



• This terrace extends as a strip fringing the valley to the west of Straid Hill (1,002). 

 It occurs about Straidarian Ho., and continues as an ever broadening band from south of 

 Ballyrory to Teenaght and Tullintrain, measuring along this stretch almost one-half mile 

 wide. It covers all the country between this and Comber Ho.andScardagh and as far south 

 along the valley of the Glenrandal Eiver as the bridge (320). On the left bank of this 

 stream it covers a considerable area, extending from the Rectory as far as Comber Church. 

 The good sections hereabout were described by Portlock (Report, p. 636). On page 639, 

 referring to these sands, he remarks that in them ' ' is seen a quiet and long-continued 

 action, probably assisted by the damming up of the channels by ice " — a truly remarkable 

 statement for that time (1843). This clear description of Portlock's requires no supple- 

 mentary remarks, other than the statement, that wherever exposed, the material invariably 

 shows the same characteristics and arrangement. Good sections were also observed at 

 Binn, south-east of Claudy, where the terrace features of flat-top and steep face are 

 magnificently shown. Traces of this terrace occur as a narrow shelf along the north side 

 of the lake. The best view of these magnificent terracic features in the Faughan and the 

 finest of the Sperrin Mountains, including the 400 and the lower terraces, is perhaps to 

 be obtained near Claudy, looking south. 



- This valley is brought out by the 500-foot contom- in PI. IX. 



