308 Proceedings of the Royal Irish Academy. 



A number of corrie-like depressions occur in Donegal, placed laterally, 

 and in a hanging position, on the sides of the major U-valleys. They 

 are independent of the structure and nature of the country rock, though 

 chiefly occurring in the granite and quartzite areas, as these form the greatest 

 elevations. They face all points of the compass, including south, south-west, 

 and south-east (e.g., those in the sides of the Gweebarra depression and the 

 hollow in the S.-E. face of Slieve League), though the majority face N. or N.-E. 

 Traces of lingering ice in these recesses are remarkably scanty; with the 

 possible exception of the drift ridge at the mouth of the eastern depression 

 in Slieve League — a ridge totally insignificant in size as compared with the 

 recess behind — no true moraine was noted in connexion with these features. 

 Certain ridges observed at the moutlis of some of these when closely examined 

 are seen to be " solid " and indicative of erosion behind them. In the absence 

 of moraines these great hollows are clearly not to be attributed to late-glacial 

 erosion. They lack, moreover, the sliarp and serrated edge along their upper 

 rim, which, with the single exception of Slieve League, is invariably beautifully 

 rounded and covered with striae and moutoniiAc forms. The rounding is in 

 all cases due to ice pouring into the hollow over the top of the bounding wall. 

 As magnificent instances of corries, showing the smooth and rounded rims 

 curving into the back of the recess, may be cited the huge amphitheatre, about 

 three miles south-west of Ardara, tlie two recesses in which lie Lough Croagh- 

 ballaghdown and Lough Adoochro respectively, in the Slievetooey Hill, 

 the depression containing Glentornan Lough, and Lough Belshade in the 

 Barnesmore Hills. As this rounding took place during the maximum phase, 

 and as corrie moraines are absent, it would appear that these depressions 

 must lie either pre- or early-glacial features, moulded by the plunging glaciers 

 of the maximum period. 



The altitude of the floors of these depressions varies somewhat over the 

 region, the highest being about 1,000 feet above sea-level, the lowest some 500 

 or GOO feet. Like the U-valleys, they are modified rejuvenation features, 

 running into the hills from the higher peneplain. They have been widened 

 and deepened by glacial erosion, acting diiefly during the maximum stage, 

 though, in the case of the cirques, most probably also by the corrie glaciers 

 of the earlier stages of the glaciation. Any arretes so produced, however, 

 would be rounded by the plunging ice, any morainic mounds and ridges 

 transported far beyond the mouth of the corries. In this way they differ 

 from the cwms of Snowdonia, where the corrie stage persisted throughout 

 the glacial period. 



The absence of corrie moraines, except in Slieve League, and the perfect 

 state of preservation of the striated surfaces produced at the maximum 



