392 MAJOR A. B. DWEKBYHOUSE ON THE [vol. lxxix, 



(b) The Valley oP the River Main. 



It will be convenient to begin the description of the deposits in 

 this valley at its southern end, as the latest movement of the ice 

 was from south to north. 



It has already been pointed out that in the Randalstown-Cooks- 

 town Junction area the Tyrone rocks disappear from the drift 

 about the line of the Midland Railway (main line), and in the 

 district on the north they are confined to a narrow strip on the 

 western side of the valley of the River Main. Thus, at Ahoghill, 

 the boulders (though chiefly of the local basalt) include a few 

 diorites and mica-schists from the Tyrone Axis. 



On the old road between Galgorm and Ballymena, in the heaps 

 of boulders picked from the neighbouring fields, only basalt and 

 one fragment of chalk were found ; and in a brickworks alongside 

 the railway, half a mile south of Ballymena Station, in a very large 

 collection of boulders I found only basalt, Silurian grit, vein- 

 quartz, flint, and rhyolite. 



North of Ballyniena, and lying between the town and Berk Hill 

 (506 feet), is an area covered by mounds of glacial gravel ; in this 

 are numerous extensive sand- and gravel-pits giving excellent 

 opportunities for determining the origin of the materials. In none 

 of these pits was I able to find any rocks from the Tyrone area. 



A point of considerable interest is the transport of fragments 

 of the local rhyolites of Quarry town and Kirkinriola to the west of 

 their outcrops, which must have been caused by the Scottish ice 

 descending the valleys of the Braid and Clogh rivers. 



As examples of these gravels, a description of the pits in two 

 localities will suffice. 



On the right of the main road from Ballymena to Ballymoney, 

 and 2 miles from the former locality, are two large pits worked for 

 sand and gravel. In the southernmost of the pits the material is 

 strongly current-bedded, and the gravel, which is 12 feet thick and 

 waterworn, rests upon the sand. There are beds and patches of 

 extremely fine gravel consisting almost entirely of basaltic debris, 

 but with numerous grains of white quartz in the sandy layers. 

 The sand dips north-westwards at 5°, and is intersected by numerous 

 small faults with throws varying from 3 to 4 inches. The coarse 

 gravel consists chiefly of basalt, but also contains Tertiary quartz- 

 rhyolite, bluish in colour (Kirkinriola type), flint, chalk, and Ailsa- 

 Craig eurite. 



In the northern pit the gravels are of considerably coarser texture, 

 and contain many large boulders. They are roughly stratified, but 

 not current-bedded. Here again basalt is predominant, the erratics 

 being Tertiary rhyolite, flint, chalk, a basalt with porphyritic 

 felspars, olivine-dolerite of Sliemish Mountain, and quartzite. 



Nearer the main road is a deposit of stratified sand at a loAver 

 level than, and apparently passing beneath, the gravels. 



At Drumbane, on the road between Balryrnena and Clogh, are 

 several pits in sand and gravel, with thin beds of red sandy boulder- 

 clay. Many of the beds of sand are black, and consist of basaltic 



