DU NOYER — NOTES ON THE GIANT's CAUSEWAY. 
5 
formed of bedded basalt which rises from the sea, the adjoining head- 
land beyond it being chalk ; thus wo 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- 
panying 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 Basalt and Chalk, Shore of Portrash, 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, exliibits numerous lines of lamination, which are 
parallel to the direction of the layers of flint (d). Numerous joints 
rather wide apart traverse the chalk layers at their upper part, 
vei-tically. 
The view (fig. 3) also from Dunluce Castle is in the opposite 
du-ection to the former, or lookmg east towards the Causeway- 
