part 3 J GLACIATION OF NORTH-EASTERN Ireland. . 383 



In the neighbourhood of The Three Islands is an extensive 

 striated surface of basalt, on which the strise run in several 

 different directions : namely, south to north, south-south-east to 

 north -north -west, and south - south - west to north-north-east. 

 Those from south-south-east to north-north-west cross, and in 

 some cases obliterate the others, thus representing the latest move- 

 ment. Other striated surfaces with striae running in the same 

 general directions occur at Gawley's Bay, Pullan Ba} r , and Doss 

 Bay farther west. 



At Pullan Bay are many big boulders on the beach, and these 

 include basalt (local), granite (Slieve Gallion), diorite, pyroxene- 

 rock, red granite, schist, andesite, and gneiss (all from Tyrone), 

 and also chalk, flint, and vein-quartz. The beach is bounded by 

 low cliffs of brown boulder-clay, which also occurs in situ on the 

 shore ; and it was from this deposit that the large boulders were 

 derived. 



A mile north of Staffordstown Station, in the same area, occur 

 boulders of basalt, pink quartz-porphyry, andesite, pyroxene-rock, 

 chalk, and flint, all derivable from the south-west. 



VI. The Central Depression north oe Lough Neagh. 

 (a) The Valley of the Lower Bann (map, fig. 6). 



In order to follow the later glaciation of this area it will be 

 necessary first to consider the deposits and drainage-channels 

 in the country north of Slieve Gallion, and in the neighbour- 

 hood of Draperstown, Magherafelt, Castledawson, and Maghera 

 (figs. 5 & 6, pp. 376 & 384). l This is a low-lying basin drained 

 by the Moyola Eiver and its tributaries, and I saw at once, on 

 visiting the area, that it had been covered by ice from the south 

 and south-east. 



It has already been noted that a great glacier flowed in a north- 

 easterly direction from the valley of The Six Towns and the high 

 ground north-west of Slieve Gallion, also that ice flowed in a 

 northerly direction along the eastern face of Slieve Gallion, over 

 the country between Moneymore and Magherafelt. 



It was obvious on the ground that the ice-flow from the direction 

 of The Six Towns, and from Glenelly and the country on the west, 

 had been extremely powerful, and my first investigations in this 

 district were undertaken with the view of ascertaining, if possible, 

 the height which the ice of this stream had reached on the hills 

 north-west of the Draperstown basin. Little information could be 

 gained on this subject from Slieve Gallion (1735 feet O.D.) except 

 the fact that that mountain had been completely overridden. 



North and west of Draperstown are several passes leading over 



1 In fig. G the place-name ' Granaghan Hill ' should appear on the hill 

 immediately north of that on which it is erroneously indicated : that is, nearer 



ISwatraffh. 



