J>art 3] GLACIATION OF NORTH-EASTERN IRELAND. 415 



Farther east, a thickness of 3 feet of brown sandy boulder-clay 

 is exposed at the base of the section. This contains Tertiary 

 basalt and many striated boulders of Carboniferous Limestone, 

 Also granites and hornblende-granites. At the road end this clay 

 thickens out to 10 feet, but its base is not exposed. 



Three-quarters of a mile farther east the cliffs are 15 feet high, 

 .and show at the base a grey clay which is very poorly exposed, and 

 then the following series : — 



(5) Coarse angular gravel. 



(4) Yellow sands (8 feet). 



(3) Contorted sands and clays (4 feet). 



(2) Layer of pebbles of Carboniferous Limestone. 



(1) Grey clay (1 foot +). 



On the beach along this section of the coast lie thousands of 

 large boulders. These include the whole suite of igneous rocks 

 from the Carlingford-Slieve Gullion massif, and also many 

 ■examples of Carboniferous Limestone and Silurian grit. Mourn e 

 Mountain granites do not occur. 



IX. Summary and Conclusions. 



In studying the glacial geology of a country three principal 

 forms of evidence are available: (1) the roches moutonnees 

 and striated surfaces ; (2) the drift-deposits, including erratics ; 

 and (3) the various types of dry channels produced by the water 

 draining away from the ice, or overflowing from temporary ice- 

 dammed lakes. 



The roches moutonnees and striated surfaces in the district 

 now under consideration have been studied by the officers of the 

 Geological Survey, and most of those which are exposed are marked 

 upon their 1-inch maps. In some cases the exact bearing of the 

 striations is given in tabular form in the explanatory memoirs 

 accompanying the sheets. This work has been done with extreme 

 care and accuracy, and in but few instances have I been able to 

 add to the list of the recorded examples, and that only in cases 

 where a new excavation has recently exposed them. 



An early attempt was made by the officers of the Geological 

 Survey, on the suggestion of the late Prof. E. Hull, to determine 

 the general direction of ice- flow over the North of Ireland by 

 means of these striated surfaces, and, as a result of their investi- 

 gations, a paper was published by J. E,. Kilroe on the Directions 

 of Ice-Flow in the North of Ireland. 1 



In this paper it is pointed out that the striations recorded on 

 the maps of the Geological Survey may be resolved into two sets 

 running approximately at right angles to each other, and these are 

 respectively attributed to (1) a glaciation by ice from Scotland, 

 and (2) a later glaciation by ice from a great central snowfield 

 (axis of glacial movement) running across the North of Ireland 



1 Q. J. G. S. vol. xliv (1888) pp. 827-33. 



