Chakleswokth — Glacial Geology of North-West of Ireland. 223 



not been detailed, afford sufficient evidence upon which to construct a western 

 limit. The line would appear to run along the northern side of the Reelan 

 Valley, swinging round somewhat to the west so as to include Cronaglack, 

 crossing the valley of the Swilly above Letterkenny, and keeping east of 

 EUistria, continuing to ]\Iilford and Mulroy Bay. 



The following notes give the main line of distribution of the erratics. 

 They are extremely abundant to the south of Stranorlar, lying scattered over 

 the surface in their hundreds, occurring both in the drifts and on the surface, 

 almost to the exclusion of boulders derived from the subjacent rocks. In the 

 valley of the Deele lUver they occur in considerable numbers, and were 

 observed along all the country from Stranorlar to Letterkenny, decreasing 

 appreciably in numbers as traced to the latter. 



The granites were seen in great profusionover all the country bordering 

 the Finn Valley, from Stranorlar to Killygordon and Liscooly, occurring ou 

 both sides of the valley, though more abundantly on its northern side. They 

 are very common indeed in the fine railway cutting at Drnmboy, north-west 

 of Lifford, fairly plentiful on the western flanks of Knockavoe, east of 

 Strabane, and in the recess to the west of the Koram Mountains. They are 

 also abundant about Ballymagorry and in the embayment extending north- 

 east from Strabane to A rtigarvan, also from Eaphoe to Letterkenny. Carvill 

 Lewis noted their presence at Pluck. They are plentifully strewn over 

 Dooish, and occur at the Glentown quarries to the south-east of this hill, and 

 over all the area of the large and broad depression in which lies Port Lough, 

 They are also exceptionally abundant and large on the north and north-west 

 flanks of Finwell Hill about Farland Point, and on the shores and southern 

 slopes of Inch Island. An occasional boulder occurs on the western flanks of 

 Greenan Hill, though in the thick drifts between the hills to the south of 

 this, granites, both large and small, are numerous. They also lie scattered in 

 considerable numbers over the floor of the " Pennyburn depression." 



The main passage of the granite-laden ice was undoubtedly along the 



present Foyle Valley, as here the boulders are largest and most numerous, e.g. 



at St. Johnstown and Garrigans, and all over the country extending northwards 



to Londonderry. They are similarly abundant on the eastern side of the valley 



from Prospect via Prehen to Londonderry. Natural sections in the vicinity 



of this city are very few, but granite boulders (usually one foot long) occur in 



great numbers, and up to three feet in length in the walls of the fields and 



roads of the neiglibourhood. 



They are common in all the drifts of Inishowen, as far north as Malin 



Head and Inishowen Head, and were encountered in all the valleys of the 



peninsula. Great numbers occur at Carndonagh. They were even observed 



[2 £'2] 



