136 Dr. "Bevlger on the Geological Features 



as subordinate beds in this granitic formation ; since on the shore at 

 Glass Drummond, a ledge of porphyritic syenite, evidently con- 

 nected with the granitic mass of the adjoining mountain, is seen 

 running out into the sea. 



If the granitic formation, above described, be identified with 

 the newer granite of the Wernerians, it may be conjectured that it 

 reposes on mica slate. 



B. Gneiss f 



Has not been noticed as occurring within the district now des- 

 cribed, although the mica slate in the north-east of Antrim some- 

 times assumes a character which it is not easy to distinguish from 

 that of this rock, 



B. 2. Mica Slate. 



Of all the primitive rocks mica slate appears to be the most 

 widely distributed over the north of Ireland. 



In Armagh, the sides of that narrow valley which separates 

 Slieve GuUen from the Slieve Girkin mountains, and contains the 

 small lake of Cum Lough, are principally composed of mica slate. 



In the north-eastern angle of Antrim, mica slate forms the pre- 

 vailing substratum through a district comprising about 40 square 

 English miles, and extending from north-west to south-east, between 

 the mountain of Knocklead (south of Ballycastle) to the valley 

 of the little river of Glendun, which empties itself into the sea at 

 'Cushendon, on the north side of Red Bay. 



Within this district, however, extensive deposits of very recent 



