294 Proceedings of the Royal Irish Academy. 



Barnes Lough, in the transverse valley of the Barnes Eiver, owes its 

 existence in part to the niorainie ridge wliich probably originally spanned 

 the valley as a terminal moraine, but of which, owing to the activity of the 

 Barnes Eiver, only a small part now remains. The remnant of the lateral 

 moraine of a slightly earlier period runs along the foot of Brown's Hill. 



Terminal moraines were observed in the Owengarve valley. The large 

 valley, containing Croaghanard Lough, possesses a broad and low morainic 

 mound situated at the lower end of the lake. The mound is probably 

 partially responsible for the lake's existence. 



The main lines of the retreat of the great Donegal Ice-sheet from the 

 several boundaries limiting the region investigated in this work have now 

 been traced. Some points are still obscure. Of these the greatest is the 

 relative importance of the Barnesmore and Derryveagh centres during the 

 later stages. Though this has in the main been clearly solved in favour of 

 the former, it has been found impossible to determine with any satisfactory 

 degree of certainty the mode of retreat in the critical area immediately 

 S.-E. of the Derryveagh Mountains. 



VIII. — The Ee-advance of the Scottish Ice. 



It is proposed in this section to sketch very briefly the scanty evidence 

 suggestive of a re-advance of tlie Scottish Ice. The first indication of such 

 an advance is furnished by the occurrence of a number of very fine roches 

 moutonndes which were observed in several places along the coastal strip 

 extending N.-E. from Moville,' and which were most clearly produced by ice 

 proceeding from the N.-E. 



In the great sinus south of the Eoyle estuary there extends a great gravel 

 sheet, the " detritic flat " of Portlock.^ Covering many square miles of 

 country, it stretches from tlie foot of the hills, where it rests against rock or 

 hummocky drift, out over the gently-shelving bottom of Lough Eoyle, 

 forming an extensive coastal plain skirting' the southern shores of the estuary 

 from its head to the Eoeat Liraavady, and continuing southwards as a narrow 

 strip to the east of the Culmore section of the Foyle as far as Londonderry.^ 

 It sends tongue-like projections into the valleys and bays of the higher 

 ■ground, e.g., round the mouth and as patches along tlie sides of the valley 

 of the Faughan. The present streams, e.g., the Faughan and the Eoe,* have 

 carved out of it a number of alluvial flats and terraces bordered by miniature 

 escarpments. 



' E.g., by the edge of the sea, just out of Moville, on the north side. 



2 Report, p. 636. 



^ The military barracks of this city are built upon it. 



* Those of the Roe are referred to by Portlock (Report, p. 636). 



