154 W. B. Wright— The Dnim/ins of South Donegal. 



truth is by careful observation of the peculiarities of form and 

 structure exhibited by these features in the areas where they are 

 most characteristically developed. 



Two such areas occur in the south of the county of Donegal in the 

 north-west of Ireland, and were examined by the writer in the 

 summer of 1910. They are both lowland districts formed of 

 Carboniferous rocks, the first lying around the village of Pettigo, 

 north of Lough Erne, and the second around the towns of Donegal 

 and Ballintra. These areas are separated by a ridge of high moorland 

 formed of metamorphic rocks and indicated by the course of the 

 400 foot contour shown on the map on Plate VIII. Such striae as have 

 been recorded in the district are also indicated on this map, and it 

 will be seen that their direction corresponds very well with that of 

 the adjoining drumlins. 



In the district lying south-east of the moorland there are several 

 rather distinct types of drumlin topography. To the north-east of 

 Pettigo elongated hills occur with axes trending south-west. Some 

 of these are composed entirely of drift, but others appear to be moulded 

 on solid cores of rock, and in general in this area it is difficult to pick 

 out the solid features from those due entirely to deposition. The 



Fig. 1. View looking south-east from Carn Upper, near Pettigo, co. Donegal, 

 across the direction of ice-motion. Gently domed drumlins of shortly oval 

 outline. 



country is deeply grooved and ridged in the direction of the ice-motion, 

 which, there is every reason to believe, was just here more constant in 

 its trend than further south-west. Such undoubted drumlins as occur 

 are elongated and of the form most aptly described as hog-backed. 

 Occasionally they show a tendency to develop a crested form similar 

 to that of the drumlins of the Ballintra district to be described below. 

 Immediately around Pettigo the predominant form of ground-plan is 

 a short oval, and the tops of the hills are gently domed without any 

 trace of a central ridge or crest. In Fig. 1 an attempt is made to 

 portray this type of drumlin topography, and the contours on the east 

 of the map in Fig. 2 also show well the character of a number of 

 drumlins of this type. Further west in the neighbourhood of 

 Carntressy and Belalt a third type of topography is in evidence. The 

 drumlins here, like those of Pettigo, are subdued and gently domed in 

 profile, but in ground-plan they take on most remarkable triangular 

 and crescentic forms, which are well shown by the contours in Fig. 2. 

 As the striae in this area prove two directions of ice-motion, and as 

 the sides of the triangles and the horns of the crescents are parallel to 

 these two directions, one is irresistiblv forced to the conclusion that 



