Geological Features of the North-east of Ireland. 131 



existence of this formation near Metz. Its thickness in Ireland has 

 not been ascertained. 



4. The Has in Ireland reposes, as in England, on beds of red and 

 variegated marie, containing gypsum and further distinguished by 

 numerous salt springs ; the marie is underlaid by a thick deposit of 

 red and variegated sandstone containing clay galls. These four 

 formations which, together with the basalt, constitute the whole 

 mass of the mountains belonging to the third system, cannot be 

 estimated as possessing a less average thickness than from 800 to 

 1000 feet : the whole system appears at the north-eastern and south- 

 western extremities to repose upon the coal formation, and its 

 associated limestone, and this again on transition or primitive rocks. 



The four formations, more particularly specified, vary conside- 

 rably in thickness in different places. The mulattoe and lias are often 

 entirely wanting, so that the chalk rests on the sandstone No. 4 : this 

 position seems to arise from the superior stratum in such cases 

 extending beyond the outgoings of one or more of the inferior strata, 

 and being thus brought into contact with beds which, when the series 

 is full, occupy a yet lower place. 



The chalk and sandstone are however remarkably constant j it 

 may indeed be said to be almost universal within this district j one 

 exception, however, is afforded by Cross hill a little to the west of 

 Fairhead, where the basalt overlies even these, and reposes imme- 

 diately on the regular coal measures of the Ballycastle district. 



The section presented at this point is also worthy of mention, 

 on account of its general resemblance with that of a part of 

 the Campsie hills, published by Col. Imrie in the Wernerian Soc. 

 Trans. Vol. 2. The whole series may be examined with the great- 

 est advantage in the neighbourhood of Belfast, where all its mem- 

 bers occur. 



R 2 



