302 Proceedings of the Royal Irish Academy. 



along the western coast, e.g., among many others, the Clady, Gweeclore> 

 Ballaghdoo and Eske Pavers.^ The rivers of Sligo show the same features. 

 To this the Erne can be no exception, and if a buried channel exists south of 

 the present line, it would seem that it must also possess rejuvenated 

 characters. 



The drainage system of the Sperriu Mountains presents many anomalies. 

 As already elaborated, the retreating Donegal ice-sheet, abutting against these 

 hills, shut the natural exits to the north, and barred all direct egress of the 

 drainage. The channels, excavated by the glaciall^'-derived streams, have in 

 several ca^es been cut to such a depth as permanently to divert and influence 

 the plan of the drainage of the hills. The coui'se of the normal drainage is 

 generally to the north-west ; that of the glacial ovei-flow channels is in almost ' 

 all cases north-eastwards. 



A notable example of this aberration is furnished by the Finglen Eiver. 

 This river, instead of pursuing its course straight forward to Finearu down 

 the wide and open valley of the Sruhan Meeuard ri\'er, to which it obviously 

 belongs, swerves sliarply to the east tlirough the narrow, gorge-like valley of 

 the Cushcapal Water, finally falling into the deep glen of the Owenrigli 

 Eiver. This diversion is aided by the moraiuie accumulation in the floor of 

 the major valley. 



Among other very good instances may be cited the Glenrandal River, 

 diverted near Stranagalwilly, and the Ballydonegan Eiver, west of 

 MuUaghash. 



These anomalous drainage lines of the Sperrin Mountains are therefore 

 vestigial inheritances of the glacial period, the streams remaining in 

 occupancy of glacial marginal channels. 



' Eunning to the west of Bessy Bell and between this hill and MuUaghcroy 

 on the west, is a very large depression in which are situated the park and 

 ducal house of JBaronscourt. It is wide and flat-floored, with very little fall 

 (about 6 feet in three miles), wliile drift occurs against its sides and on its 

 floor. Its present stream is small and wholly incapable of excavating such a 

 large feature. The valley is undoubtedly pre- glacial in origin. 



The valley of the Strule Eiver from north of Mountjoy to Newtown 

 Stewart is in places a rock gorge, and in general so narrow as to forbid the 

 supposition that this was the ancient course of the northward-flowing 

 drainage. 



The ice shrinking we.stwaid along the broad flat of the Faiiy Water, as 

 already shown, impounded the drainage of the liigh land of Mullaghearn and 



' The waterfalls and deep gorges exhibited by the streams flowiug into Lough Foyle 

 down the eastern slopes of Inishowen would also seem to be due to rejuvenation. 



