200 Proceedings of the Royal Irish Academy. 



This has been clone by Mr. W.B. Wright in hif5 paper on the drumlin country 

 of Pettigo.' It may, however, be here remarked, in view of some divergence 

 of opinion on the position of the blunt and higher end of the drumlin, that 

 this was found in general to be situated towards the stoss side of the mound, 

 the narrower, and more gently sloping end towards the lee. 



This peculiar topography extends from Killybegs on the west, round the 

 whole of the northern shores of Donegal Bay to Donegal town at the head of 

 the bay, and inland generally to the foot of the hills bounding the coastal 

 plain. It is equally well developed along the eastern shores of the bay, as far 

 as and even beyond Ballyshannon and the Eiver Erne, in the country east of 

 Pettigo, and north of Castle Caldwell. 



In certain areas the drumlins pass insensibly into the hill country behind, 

 in which direction their drift cover becomes ever thinner at the expense of 

 the rock core. This gradual transition from undoubted drumlin to equally 

 pronounced hill country, characterized by rounded and moulded " solid " forms, 

 is well seen in the area south of the Eglish valley, where the huge drumlin- 

 like mounds, of much larger dimensions than usual, rise above the general 

 surface of the country, their larger axes parallel with the general direction of 

 the glaciation of the district. A. similar transition takes place over the 

 country to the north-east of Ederny, and to the south-east of Donegal town. 

 In all these areas it is difficult or even impossible to draw a line separating 

 the true drift drumlin from the moulded " solid " feature. This behaviour of 

 the drumlins would appear to support the erosion cheory of their origin. 



In other areas there exists between the drumlin country and the highland 

 a strip of irregular and very broken surface, as can be observed in the district 

 extending between Barnesmore and the Clogher valley (lying east of Donegal 

 town), and also along part of the eastern margin of the Glengesh Plateau. 

 The transition forms occur therefore where the ground rises gradually into 

 the hills, the discontinuity of form where the hills fall fairly steeply to the 

 plain. 



Between the ridges and mounds lie small lakes and ponds, while water- 

 logged hollows and flats of peat or alluvial soil indicate the sites of former 

 drift-dammed lakes. As examples of such inter-drumlin lakes may be cited 

 Drunioske L., DrumhomeL., and Birra L., all in the vicinity of Eossnowlagh, 

 and Trumnian L., to the north-east of Bridge Town ; L. Ardnagossan and the 

 lough at TuUynagran are of similar origin. These inter-drumlin lakes are also 

 extremely numerous in the lowland situated to the east of Donegal Bay, 



' The Drumlin Topography of South Donegal : Geol. Mag. , N.S. , Dec. v, vol. ix (1912), 

 pp. 153-9. 



