the North East of Ireland. 213 



some places appearing to alternate with, a very remarkable rock 

 which has been the subject of much discussion among the sup- 

 porters of opposite theories. 



It is a flinty slate, exactly similar to the indurated slate clay 

 which forms the wall of the Carrick Mawr dyke, in the Ballycastle 

 collieries ; and the analogy is rendered the more striking, from the 

 fuKher resemblance of the greenstone of that dyke to the green- 

 stone of these cliffs. In this flinty slate are contained numerous 

 impressions of cornua ammonis invested with pyrites, the shells 

 being similar to those found in the slate clay underlying the chalk 

 near Ballintoy. 



The advocates of the Neptunian theory consider this rock as a 

 variety of basalt, and refer triumphantly to its included fossils, as 

 affording a conclusive argument against the Volcanists. 



Professor Playfair, on the other hand, expresses his belief that 

 " the rock containing the shells is the schistus or stratified stone, 

 which serves as the base of the basaltes, and which has acquired an 

 high degree of induration by the vicinity of the great ignited mass 

 of whinstone." See illustrations of the Huttonian theory. 



The resemblance of this rock to the indurated slate-clay of Car- 

 rickmawr, and the identity of its fossils with those of the slate- clay 

 underlying the chalk near Ballintoy, together with the relative po- 

 sition of Portrush and of the chalky cHffson the east, appeared to us 

 to give the greatest weight to this very ingenious conjecture ; and 

 we felt convinced while examining the spot, that the rock was no 

 other than the slate-clay of the lias formation In an indurated state. 



The remaining portion of the section will sufficiently explain 

 itself: it terminates where the secondary formations turning to the 

 south finally quit the coast. The headland of Macgilligan, the most 

 northern point of the mountain range formed by their escarpment 



