CHA.RLESWOETH — Glacial Geologij of North-Wed of TrelamL 261 



dry, and cut through the earlier-formed moraines and the " aolid." In this, 

 and the neiglibouring gaps, the rapid descent of the moraines along the 

 sides of the liills to the floor of tlie valley suggests the equally rapid fall of 

 the ice-surface at the snout of the glacier. Of the several lakes held up by 

 the moraines, the largest is Lough Tea itself. 



Similar morainic arrangement characterizes all the other breaks in this 

 metaniorphic range. E\en the smaller gaps, e.g. that between Beleevnamore 

 Mountain and Evishbrack Mountain, had small glaciers thrust into 

 them. It is manifestly impossible to give details of all these morainic ridges; 

 the map indicates sufficiently clearly their position and mode of arrangement.^ 

 These moraines are frequently asymmetrical about the axes of the gaps, the 

 asymmetry pointing to a push from the west, oblique to the axes. This is 

 perhaps most easily recognisable in the group of moraines S.-W. of Beleevna- 

 more Mountain. 



The retreat can be readily followed from Draperstown south-westward. 

 Though the drift is piled np more or less smoothly against the sides of 

 Mullaghturk, farther north along this side of the corridor, definite morainic 

 features become conspicuous. The finest of these are the prominent mounds 

 and ridges, over a mile in length, observed on the eastern slopes of Slievea- 

 vaddy, at an altitude of about 800 feet, O.D. Eidges of even greater size, 

 in part of morainic origin, occur near Draperstown. The eastward diversion 

 of the streams by drift deposition, to which reference will be made later (p. 267), 

 is well shown on the eastern flanks of the hills, W. of the Moyola valley. 



The most magnificent moraines, however, are those skirting the southern 

 edge of the corridor, located frequently well up on the hillside, and swinging 

 across the breaks in the range, e.g. the pronounced hummocky Crockundun 

 Hills (K-E. of L. Fea), Wolf Hill (W. of Fir Mountain) and the ridges at 

 Dunnamore and west of Evishanoran Mountain. These are the gigantic 

 lateral moraines of this Tyrone glacier, formed after the lobes thrust through 

 the gaps had completely shrunk back to the parent glacier out of which 

 they had sprung. Other morainic mounds and ridges, less conspicuously 

 displayed, traverse the wide floor of the depression. The ice-foot along 

 which they were formed stood in ponded water. The moraines sweeping 

 across the gaps to the south-east effectually closed these against escape of 

 drainage from the " Corridor." In consequence, the comparatively shallow 

 lake, held up by the barrier of the receding ice on the south-west, and fed 

 by melt waters, drained by a channel excavated in part in " solid," between 



' Reference to a few of these mounds and ridges and to some of those occurring in the 

 adjacent areas and dealt with below is made in the Geol. Survey Memoir's, Slieet 26 

 (pp. 21, 22) and Sheet 34 (p. 21). 



