Charlesworth — Glacial Geology of North-West of Ireland. 199 



1. The country along tlie Ice-slicd. 



The Bluestack and Barnesmore granite hills situate iu the central section 

 of the ice-shed, exhibit smooth moutonnec summits, beautifully rounded, 

 shoulders, and steep glaciated sides which descend sharply iuto broad U 

 valleys. The striae hear generally N.E.-S.W. — i e., parallel witli the axes of 

 the valleys. 



On the south side of the granite massif, where the surface falls steeply to 

 the country occupied by the sedimentary and schistose rocks, a series of rock- 

 basins — e.g., L. Aderry, L. Ankeeran, L. GuUaduff — were excavated in the 

 floors of the smaller steps by which the big break is accomplished while the 

 vertical rock faces of the steps are frequently striated. 



In the elevated country of schist which stretches to the south-east of the 

 Barnesmore hills, the same parting of the ice is also recognisable. Moorland 

 country for the most part, the evidence is not so easily obtained. Tet the 

 few striae' observed, the form of the ground, the roches moutonnees, the position 

 of the perched blocks, the ridges of drift within the area, and the drumlin 

 mounds in the adjacent country serve as unmistakable signs of the direction 

 of ice-motion. 



2. The Brumlin Belt rxrouncl Donegal Bay. 



The drumlius of the country skirting JJonegal Bay are developed with a 

 sharpness of outline and clearness of arrangement nowhere equalled or 

 approached in the whole of the region examined. Tliey are, perhaps, most 

 finely exhibited in the neighbourhood of Donegal town. The contoured maps 

 of the country around and bordering on Donegal Bay — e.g., the Ordnance 

 map of Donegal town (Sheet 23) — bring this out most strikingly. Generally 

 these features are separate, only occasionally coalescing, overlapping, or 

 mutually interfering. 



Some of these mounds are doubtless fashioned in rock by direct sub- 

 glacial erosion, possessing a large " solid " core and merely a thin coating of 

 boulder-clay, thickening from the crest to the margin. More particularly is 

 this true of those distributed on the inland side of the drumlin belt, where 

 the " solid " hills begin. Some even prove to be entirely " solid " features — 

 e.g., the basalt hill near Donegal town. 



It is not proposed to discuss here the question of the form of the drumlius. 



' The striae, occurring north of Clogher Hill at the head of the Leaghany E,iver, and 

 marked on Mr. W. B. Wright's map (The Drumlin Topography of South Donegal, 

 PI. VIII), trend, I think, east, not west, as there suggested. Those recorded from two 

 localities 4 miles west and south-west respectively of Ealleter, were certainly produced 

 by ice proceeding eastward in the opposite direction to that there represented. 



