(Jharlesworth — Glacial Geology of North-West of Ireland. 301 



crossing the Carboniferous Limestone and other rocks of this formation to 

 their boundary with the members of the metaniorphic series, then following 

 the line of junction to the sea. This change of direction is accompanied by 

 an equally pronounced transformation in the character of the valley, the 

 river, below Belleek, flowing by a series of falls and rapids along a rocky 

 gorge bounded by lofty and precipitous sides to the Falls of Ballyshannon 

 near the sea. Between Belleek and Ballyshannon, a distance of some six 

 miles, the liiver Erne falls 143 feet ; from Enniskillen to Belleek, a distance 

 of roughly twenty-four miles, the fall is 10 feet. 



This coincidence in the abrupt change in direction with the remarkable 

 change in the scenery and type of valley is highly suggestive of a glacial 

 diversion below Belleek, and of the existence of an old pre-glacial line of 

 drainage west of Belleek in a line roughly continuous with that of the valley 

 above this town. The great areas of very thick turf, wliich conceals both the 

 '■ solid " and the drift of this country, render it impossible to trace the course 

 of such a drift-filled valley,' while the vast accumulations of sand, forming 

 the present coast-line north of ]5undoran, forbid all attempts to discover its 

 seaward termination. The adequacy of post-glacial erosion to excavate a 

 gorge of such magnitude can scarcely be questioned when the well-jointed 

 and bedded nature of the Carboniferous Limestone and the volume of the 

 Erne are remembered. On any other view the coincidence in the change 

 of direction and character of the present Erne valley would be remarkable 

 indeed. 



An examination of the Admiralty Chart of Lough Erne shows a small area 

 of the lake floor to be below sea-level; the greatest depth is 226 feet;^ the 

 lake surface is 149 feet above sea-level. "Were the gorge of the Eiver Erne 

 below Belleek a diversion feature, and the pre-glacial river perfectly graded, 

 it would seem that Lough I'^rne, except as a very small and comparatively 

 shallow lake, could not have had a pre-glacial existence.' 



Another factor, which can be only briefly referred to in this paper, may, 

 however, not be lost sight of, namely, a pionounced and unmistakable 

 rejuvenation of the rivers of N.-W. Ireland, more especially of those mouthing 



' The Geoliigical Survey suppose a considerable fault to run along or near this line, 

 throwing down the Calp against the L. Limestone Group. This would appear to have 

 some siguilicance. The fault probably guided the pre-ghicial drainage. 



^ The deepest spot is located slightly over half a mile almost due north of Cloyaduff 

 Point.- 



' A fortiori would this be the case if the bed of the valley, like that of the Liftey or 

 Lagau were belovv sea-level ; the pre-glacial floor of the Liffey is about 30 feet below 

 sea-level (Meui. G-eol. Surv., Geology of the Country around Dublin (1903), p. 89), that 

 of the Lagan, about 2U0 feet. (Mem. Geol. Surv., Geology of the Country around 

 Belfast (1904), p. 64.) 



U.l..\. PROC, VOL. XXXVI, SKOT. B. [2 Jtj 



