64 Scientific Proceedings, Royal Dublin Society. 



distance eastward, it may be noticed that the hill is flat -topped — a 

 feature with which one becomes familiar in a Carboniferous country, 

 such as that forming the opposite shore of Donegal Bay, and 

 illustrated on so grand a scale in Benbulben, and other Leitrim and 

 Sligo hills. This feature is but just noticeable in Slieve League, 

 and might pass unobserved by one not acquainted with its geological 

 history. 



During the progress of my Survey work in the vicinity of 

 Carrick, I noticed that these beds consisted of white compact sand- 

 stone, not easily distinguishable at first sight from partially- formed 

 quartzite ; associated with conglomerate and breccia, which contain 

 pebbles of quartzite, and pink and white quartz. I did not then 

 suspect what Formation they represented, and merely noted them 

 as constituting a peculiar band in the quartzite series of Slieve 

 League. Neither did the occurrence of conglomerate strike me as 

 surprising; for it may be mentioned that at various horizons in the 

 quartzite series occur pebble-beds, and notably in the Glencolomb- 

 kille district. One of these I had observed in the cliff forming the 

 south wall of the western corry of Slieve League. Similar pebble- 

 beds are to be seen along the base of the sea-cliff, and in striking 

 development on the shore of Malin Bay, where the quartzite area 

 spreads out westward, beyond the adjoining hill (Leahan.) The 

 pebbles in these beds consist chiefly of red and gray granite, up to 

 9" in diameter, and quartzite, with a few of mica schist and fine- 

 grained gray gneiss: all embedded in graywhacke, quartzite, or 

 calcareous matrix. The occurrence of these pebbles indicate the 

 former existence of Archcean land at no great distance, while a 

 portion at least of the supposed Silurian Formation of the locality 

 was in process of deposition. 



During a recent visit of Dr. Greikie to the county of Donegal, 

 he arranged to ascend Slieve League, being especially desirous of 

 seeing the conglomerates referred to. This he did on the 24th 

 October, accompanied by two of my colleagues and myself. We 

 reached the summit of the central mass, after a climb along the 

 brow of the cliff by Bunglass, and, arriving there, had little 

 difficulty in deciding that the majority of the pebbles consisted of 

 quartzite. The similarity to a Carboniferous pebbly deposit was 

 very apparent — indeed this was suggested and accepted as we pro- 

 ceeded, but more as a general than as a decisive fact. Thus the true 



