38S MAJOR A. R. DWERRYHOTJSE ON THE [vol. lxxix, 



escarpment, and rises into summits at 893, 900. and 956 feet 

 respectively. 



North and south of this ridge are passes leading over into the 

 Roe Valley, and each of these carries a glacial drainage-channel 

 terminating westwards in a dry waterfall, below which is a short 

 gorge. These are locally known as 'pots'; the northern one is at 

 Pot Bridge and is called Legavannon Pot, while the southern one 

 is called Legananam Pot. These ' pots ' undoubtedly took the 

 drainage of a lake temporarily held up in the Agivey Basin by the 

 ice of the Bann Valley. 



The floor of the Agivey Basin lies between the 400- and the 

 500-foot contours, and is intersected by several lines of moraine 

 which are partly buried by peat and alluvium. These 1 take to be 

 lateral moraines of the Bann Valley Glacier, and I believe that they 

 belong to the same series as that which will now be described. 



The lower end of the basin is closed by a great lateral moraine 

 of the Bann Valley Glacier which stretches from the spur of Cool- 

 coscreaghan on the south to the high land west of Garvagh on the 

 north. The river has been forced over to the northern side of the 

 valley, and escapes by a gorge 100 feet deep cut through basalt. 



There is a section in the moraine on the right bank of the river, 

 immediately below Errigal Bridge, which shows brown saiuby drift 

 resting upon basalt ; and in gravel-pits close by similar material is 

 exposed, containing basalt, schist, flint, vein-quartz, and a coarse 

 dioritic rock from the Tyrone Axis. The sand is very ' dirty', and 

 there is some laminated clay without stones. 



The western (outer) face of the moraine is very steep, and about 

 100 feet high, and a small stream flows northwards through the 

 flat ground at its foot to join the Agivey immediately above 

 Errigal Bridge. 



The morainic belt is about a mile wide, and at its inner edge 

 near Lower Magheramore is a large gravel-pit, showing a section 

 30 feet deep in gravels which dip south-westwards. The materials 

 are similar to those of the great moraine, and include basalt, iron- 

 stone, schist, white granite, vein-quartz, and Slieve Gallion granite. 



Near the head of the Agive} r Basin, on its southern side, are 

 long gentle slopes leading up to Cam Hill and Benbradagh. 

 These slopes include the townlands of Brishey, Evishagaran, and 

 Cruckanim, and are heavily covered with drift, sections of which 

 are exposed in numerous stream-courses. The drift consists of red 

 boulder-clay below and gravels above. The material is all such as 

 could be derived from the immediate neighbourhood. 



The streams contain only basalt-boulders in their upper parts, 

 but some of schist appear lower down, as soon as the schist outcrop 

 has been reached. The ice which brought this material must have 

 come from the south-west, but whether from the ridge itself or 

 from the country beyond, I was unable to ascertain. 



In the valley of the Gelvin River below Legananam Pot, there is 

 an extensive lake-terrace at 500 feet O.D., consisting of red sandy 



