Charlesworth — Glacial Geology of North-West of Ireland. 201 



between Donegal town, Ballyshannon, and Pettigo. That these are due to 

 impoundmg of the drainage by druniliiis, and not to solution of the soluble 

 carboniferous limestone, is proved by their equal abundance on the relatively 

 insoluble schist. 



The drumlins have also I'egulated the course of the drainage, ami caused 

 the streams in general to flow parallel with the drunilin trend.' 



'I'he drumlin type of scenery is also cliaracteristic of the fertile country 

 encircling Lough Erne, the finest development being found along its eastern 

 shorCsS. Here the numerous inter-drumlin lakes include L. Bresk, White L., 

 and Ballydoolagh L., while there are also present, as in the major drumlin 

 country, large and small areas of turf, as near Mosstield Lower, marking the 

 position of infilled lakes. 'J'he islets in Lough Erne, especially those at the 

 Enniskillen end of the lake, are formed of one or more drumlins. These also 

 form the promontories jutting into the lake, while in other cases they separate 

 small lakelets from the main sheet of water. 



These drumlins strikingly demonstrate the lines of ice-flow. They sweep 

 round into Donegal Bay in wide swinging curves, their trend governed in part 

 by tlie contours of the adjacent high ground, and running parallel with the 

 general direction in which the drift has travelled. Thus their course, which 

 towards the west of the belt north of Killybegs is approximately north- 

 south, swings gradually round to east-west, in the neighbourhood of Bally- 

 shannon. Near Donegal town, intermediate in position, the direction is 

 likewise intermediate, north-east, south-west. An inspection of the map^ will 

 show this change in the direction of the drumlins, and their coincidence with 

 the striae. These, on account of the thickness and widespread character of 

 the drift, are by no means plentiful. A number were, however, observed by 

 the officers of the Geological Survey and by myself. 



The truncated ends of the drumlins along the coast furnish undoubtedly 

 the finest opportunity for the study of the nature and composition of the 

 drift. When these are supplemented by road and railway cuttings, sections 

 in stream and river banks, the nature of the drift can be quite readily ascer- 

 tained ; but as this everywhere shows the same characters and composition, 

 boulders and matrix alike being derived from the granite, metamorphic, and 

 carboniferous rocks, individual mention will be made of but few exposures. 



' They have also greatly influenced the road-directiuus, e.g., the main road nmniiig 



north from Ballyshannon to Laghy through Ballintra. This road, like so many others 



ill this drumlin belt, winds in a pronouncedly zig-zag manner along the valleys of 



■ accumulation between the mounds, while some of the older roads, esi^ecially those crossing 



the belt transversely to the stream of drumlins, bear a strong resemblance to a switch-back. 



^ All the drumlins here marked have been carefully reduced from my field maps. 



