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XXII. 



UN DIRECTIONS OF ICE-FLOW IN THE NOETH OF IRE- 

 LAND AS DETERMINED BY THE OBSERVATIONS OF 

 THE GEOLOGICAL SURVEY. By J. R. KILROE, H. M. 



Geological Survey, Ireland. 



[Read April 18, 1888.] 



The field observations of the Geological Survey, Ireland, being 

 completed, it was considered desirable by the Directors to represent 

 those bearing upon glacial phenomena in the northern half of the 

 country on a general map, scale ten miles to one inch. In trans- 

 ferring the observations from the inch sheets already published, 

 and those in the course of preparation, it became apparent that the 

 strife maintain two definite directions almost at right angles to each 

 other. At a comparatively trifling number of points the striae do 

 not trend in either of the two prevailing directions, and are doubt- 

 less attributable to local ice-flows, which proceeded from miuor 

 independent glacial systems at some period of the ice age. 



The two sets of above mentioned striae are observable only 

 north of a line drawn from Galway Bay to Strangford Lough; 

 and as it is difficult to conceive how both sets could be the result of 

 the same ice-movement, their existence is a very suggestive fact. 

 This difficulty may be estimated when it is stated that both sets 

 have been observed on the same flat surface in several instances ; 

 and occur alike in valleys and on the flanks and summits of some 

 of the highest hills. 



Directions of Strics. — Of these two sets of strise the direction of one 

 is north to north-west, which, as evidence of ice-movement, will be 

 considered hereafter ; and that of the other is W. 25 S. swinging 

 round to west in Donegal, and south-west towards Galway Bay. 

 This westward direction is remarkably persistent, whether at 1200 

 feet above the sea near Glenarm ; 1,250 feet in Slieve Beagh, county 

 Tyrone; 1,100 in the Nephin group, or at the sea level near 

 Belfast, Londonderry, or Sligo. To account for this uniformity of 

 direction we must conceive the passage of an ice-sheet across the 



