Chaklesworth— Glacial Geology of Noflh- West of Ireland. 22 1 



Point, at the head of McSwyne's Bay ; indeed, beyond here they are quite 

 scarce. Only a very occasional boulder was detected in the peninsulas runninu 

 south to the east and west of Killybegs Bay. The absence of granite boulders 

 at Malin Beg in the drifts already alluded to proves that the main granite- 

 bearing ice from Barnesinore passed far from the siiore down the central part 

 of Donegal Bay, and that tiie ice .skirting this coast contained not even a 

 straggler of this granite. 



Tjarge granite boulders were observed to an altitude of 1,200 feet along 

 the eastern flanks of the nietamorphic mountain of Caraween and on the 

 adjacent hills. At Ivy Bridge, over the Owentocker River, several large 

 granite erratics were noticed, while other large blocks of the rock occur in 

 considerable numbers all down the valley below this point. Small boulders 

 were detected at intervals as far as and along the eastern foot of the Glengesh 

 Plateau, where towards its northern end they occur well up the slopes. As 

 no granite of any description was encountered in the Glengesh drifts, the 

 limit of the Barnesmore granite boulder country in this direction must be 

 regarded as roughly coincident with the eastern foot of the plateau. 



To the north-west of the Barnesmore Hills the limits of the boulder dispersal 

 cannot be so accurately laid down. An occasional erratic from these hills 

 (probably from Lavagh More, 2,211) has gained access to the valley of the 

 Stracashel Eiver, proving ice-motion down this valley from the east. In 

 the upper part of the Owenroe Eiver, e.g. at Martin's Bridge, the stream 

 sections show well-rounded.granites from this source, while occasional boulders 

 were observed at intervals all the way down the valley as far as Crockbrack. 

 Pieces of granite occur in the Pinn valley moraine, at the western end of 

 Lough Pinn. Parther west, these boulders become inextricably mixed up 

 with the erratics from the Donegal granite outcrop, so that no line of 

 demarcation of the Barnesmore granite boulder country in this direction has 

 been inserted on the accompanying maps. 



In the following description of the dispersal, north of the axis, it is 

 proposed to delineate the approximate limits of the fan on the west, south, 

 and east, and to locate the main track. 



Occasional granite boulders rest on the surface in the valley of the Eeelan 

 liiver. None were detected in the drift sections in. the upper part of the 

 Pinn Valley until its confluence with the Eeelan Elvers was reached, where 

 in the railway section near Cloghanmore, a few small pebbles were observed. 

 Though these were fairly common, not a single large boulder of granite was 

 encountered. Here, therefore, we appear to be on the fringe of the fan of the 

 granitic drift. 



?,.-|.A, PROC, VOL. XXXVI, SKCI. B. [2 E\ 



