374 MAJOR A. E. DWERRYHOUSE ON THE [vol. lxxix,. 



great amphitheatre of Sallagh Braes, the country is covered with 

 the northern drift, the ice having passed southwards along the 

 foot of the escarpment into the valley of the Larne Water, at the 

 head of which stream it passed over into the valley of the Six Mile 

 Water, and thence by Ballynure and Ballyclare, to Antrim and 

 Lough Neagh. This arm of the Scottish ice picked up and carried 

 with it large quantities of the Tertiary rhyolite of Tarclree Moun- 

 tain, boulders of which form so conspicuous an ingredient of the 

 gravels near the town of Antrim. 



Through the col between the head of the Larne Water and the 

 Six Mile Water is a large overflow-channel falling south-westwards,, 

 and on its flanks are numerous drumlins, the long axes of which 

 are parallel to the channel. The light railway from Larne to^ 

 Ballymena passes through this channel. 



The peninsula of Island Magee was glaciated from north-west; 

 to south-east by the Scottish ice, and the deposits (both boulder- 

 clay and gravel) contain Ailsa Craig eurite, basalt, Carboniferous 

 Limestone, chalk, flint, and the purple porphyrite of Cushendall. 



From Larne southwards the coastal strip of low ground is drift- 

 covered in many parts, although the covering does not appear to 

 be very thick, as the solid rocks crop out in many places. 



In the Grlenoe valley a lake was held up by the ice at one stage 

 of its retreat, and its waters overflowed by a well-marked channel 

 into the valley of the Copeland Water on the south. 



The Triassic country from Carrickfergus to the foot of the Cave 

 Hill at Belfast is also covered by a variable thickness of northern 

 drift, here made up very largely of the debris of the local Trias. 



On the basalt escarpment of Knockagh, near Greenisland, are 

 two dry gaps of the ' in-and-out ' type ; but the country did not 

 lend itself to the formation of extensive lakes. 



IV. The Belfast Valley. 



The Belfast Valley and its northward continuation (Belfast 

 Lough) lie on a belt of soft Triassic rocks ; they are bounded on 

 the east by the Silurian uplands of County Down, and on the west 

 by the basalt escarpment. The drifts of the valley have been well 

 described in the Geological Survey Memoirs, 1 wherefore it is not 

 necessary to enter into any great detail here. 



The lowest deposit appears to be a red boulder-clay with basalt, 

 Silurian grit, chalk, flint, Ailsa Craig eurite, and fragmentary 

 marine shells ; but the most conspicuous accumulations are sands 

 and gravels. 



Running down the centre of the depression, between the valley of 

 the Lagan and that of the Blackstaff, is a broken ridge of red sand, 

 the ' Malone Sands ' of the Geological Survey. These ' sands ' 

 consist almost entirely of re-assorted Triassic sand and marl. 



1 ' The Geology of the Country around Belfast ' Mem. Geol. Surv. Ireland, 

 1904. 



