Straiigrapliical Geology. 



83 



Bay, revealing the basement of Lias over a considerable 



area. 



At Portrush, beds of Lower Lias occur on the shore near 

 the ladies' bathing place. This rock has a classic reputa- 

 tion, as it was one of the arguments adduced by the 

 Neptunists, about 1799, to prove the aqueous origin of the 

 basalt. The rock is a dark indurated shale, breaking with 

 a conchoidal fracture, frequently across the planes of lam- 

 ination, so that in hand specimens it was easily mistaken for 



INr)UKA I 1 



basalt. It contains, however, numerous fossils — chiefly 

 ammonites — along certain zones, but these are very difficult 

 to extract, owing to the splintery nature of the rock. 

 Similar rocks are to be observed in The Skerries, a small 

 group of islands off the coast at Portrush. The unusual 

 character assumed by the Lias in these localities is due to 

 the hardening and baking produced by the neighbouring 

 masses of basalt and dolerite. 



Only the Lower and Middle beds of the Lias are repre- 

 sented in Ireland, the Upper Lias being absent; but it is 



