206 Proceedings of the Royal Irish Academy. 



Tlie drainage from the ice-fronb, the several retreat positions of which are 

 marked by tliese numerous morainic ridges, was effected by many channels 

 now used by insignificant streams, in all cases mucli too small to have 

 excavated their valleys. These have been omitted from the map, as their 

 insertion would only lead to confusion. They are, however, recognized in the 

 field with great facility, their remarkable freshness rendeiing possible the 

 restoration of the glacial happenings, the manner of accumulation, and the 

 system of drainage with an ease and degree of certainty rarely equalled. 



3. Slieve Beagh and the Clogher Vcdiey. 

 Some of the earliest moraines, formed in the withdrawal from the region of 

 Dnndalk and the country north of the Central Plain, are represented by the 

 series of irregular ridges observed in the neighbourhood of Castleblayney and 

 in various places south of Keady. Similar recessional features with closely 

 associated ontwash fans underlie the demesnes of Glaslough, Caledon, 'J'y'ia", 

 Abbey and Killylea. These morainic ridges trend roughly N.-E.-S.-W., 

 almost at right angles to the direction of the drumliiis and of the striae of 

 the district.^ These features were regarded by T. Hallissy- as drumlins, of 

 whicli in this area he distinguished two sets, the one trending N.-E.-S.-W., 

 the other bearing S.-S.-E.^ Of the true drnndin character of the latter, there 

 can be no doubt ; their form is characteristic and their direction coincident 

 with that of the striae. With reference to the former set Mr. T. Hallissy 

 remarks : — 



" It becomes a problem of some difficulty to account for the 

 orientation of those drumlins which point north-east and south-west." 



As already pointed out (p. 194), he hesitatingly ascribed them to the 



earlier Scottish giaciation from the north-east ; their preservation during the 



supposed late giaciation from the " Central Axis " lie explained as follows : — 



"As the latter set of drumlins N.-E.-S.-W. are situated on part of 



the axis of precipitation from which the Irisli ice-sheet was fed, the 



mounds might easily have been protected from subsequent disturbance 



by an overlying stratum of snow or ice, which remained in a condition 



of static equilibrium. It is easy to imagine how this basal layer of the 



central ice did not take part in the general radial ice-movement, while 



that overlying it flowed outwards, impelled by the shearing stresses set 



up by gravitation " (p. 16). 



' A Uat of striae is given in the Geol. Survey Mem., Sheet 58 (2nd. Edit.), 1914, 

 p. 18 ; see also map acoompauyiug this paper (PI. IX). 



- Ibid., p. 15. 



5 These two sets are repi-esented on the map, fig 1, of the Monaghan Memoir. The 

 drumlins photographed in PI. II (facing p. 16) of this Memoir belong to the set going 

 S.-S.-E 



