part 3] THE GLACIATTON" OF NORTH-EASTERN IRELAND. 377 



How far the northern ice penetrated in this south-westerly 

 direction it is at present impossible to say, so long and severe 

 was the south-eastward ice-flow which followed that all traces 

 be} r ond occasional erratic pebbles have been removed. For this 

 reason the features which will now be described are those due 

 to the western ice. 



Slieve Gallion (Ordnance Survey, 1-inch map, Sheets 26 &27; 

 see also map, fig. 5) forms the eastern bulwark of a mass of high 

 ground made up of an igneous and schistose complex, extending in 

 a north-westerly direction to the Sperrin Mountains and south- 

 westwards to Carrickmore and Beragh. This mass of high ground 

 will be designated the Tyrone Axis. 



The ridge of which Slieve Gallion forms the highest point is 

 continued in a south-westerly direction by the summits of Fir 

 Mountain (1193 feet O.D.) and Beleevnamore Mountain (1257 

 feet), and north of this line of hills lies a great undulating 

 plateau in which is the valley of The Six Towns. 



Up to a very late period of the glaciation this area was occupied 

 by a large glacier which flowed north-eastwards over the site 

 of Draperstovvn. That flow is indicated by the striatums, by the 

 transport of local material, and by the fine series of lateral 

 moraines in the neighbourhood of Lough Fea. A very good example 

 of ' crag and tail ' is to be seen at Craigamullen, 2 miles west of 

 Lough Fea, where boulders of the local pyroxenic rocks can be 

 traced in enormous numbers north-east of the outcrop. 



This Six Towns Glacier pushed tongues of ice through the 

 valleys between Slieve Gallion and Fir Mountain, and between Fir 

 Mountain and Beleevnamore, wherefore frontal moraines of these 

 lobes, produced during the retreat, form very conspicuous features 

 near Lough Fea and at Wolfs Hills and Friars Rock. 



A hornblende-granite, 1 which occurs in situ near Lissan, has a 

 very wide and peculiar distribution. It has been carried up the 

 valley past Lough Fea, is present in considerable quantity in the 

 moraines known as the Crockandun Hills, and a train of its 

 boulders runs north-eastwards into the valley of the White Water. 

 This indicates a movement of ice through the Lissan valley from 

 south-east to north-west at an early stage ; but the frontal moraines 

 mentioned above indicate a flow in the opposite direction at a later 

 period. 



There is no doubt that the ice north-west of the great ridge was 

 confluent with that on the south-east at one stage, and ice may 

 well have flowed through the Lissan valley first in one direction, 

 and then in the other, in. response to varying thrusts, as one or 

 other of the great glaciers was in the ascendancy. 



In addition to the distribution described above, the Lissan 

 granite is to be found abundantly in the drift south-east and east 

 of Slieve Gallion : for instance, at Moneymore, and on the shores 

 of Lough Neagh at Ballyronan and Toome. 



1 Indicated on the Geological Survey map as ' syenite '. 



2 n 2 



