DU NOYER NOTES ON THE GIANT'S CAUSEWAY. 



5 



formed of bedded basalt wliich rises from the sea, the adjoining head- 

 land beyond it being chalk ; thus we have an example of the latter 

 kind of junction between these two rocks, as the supposition of their 

 being brought together by a fault is not tenable. 



To make this paper more complete I have introduced the accom- 

 panymg sketch of the junction of the basalt and chalk on the Port- 

 rush shore, as showing that fact more in detail. 



Lign. 2.— Junction of BascOlt and Chalk, Shore of Portrush, Co. Deny. 



a. Amorphous basalt, becoming so decomposed in its lower portion 

 as to resemble dark brown earthy shale. 



h. A layer of drift-flints, water- worn, enclosed in what is now 

 hardened, or baked chalk-mud — the flints being most numerous at the 

 bottom of the deposit. This rests on the erroded surface of the 

 chalk proper (c), showing that before the deposition of the basalt, that 

 rock had been subjected to forces of sub-marine denudation, and that 

 the basalt flowed over it while so submerged. The chalk, though not 

 distinctly bedded, exhibits numerous lines of lamination, which are 

 parallel to the direction of the layers of flint (cl). Numerous joints 

 rather wide apart traverse the chalk layers at their upper part, 

 vertically. 



The view (fig. 3) also from Dunluce Castle is in the opposite 

 direction to the former, or looking east towards the Causeway- 



