of Derry and Antrim. 105 



server on his approach, is, that although both the promon- 

 tory itself, and the strata composing it, ascend to the north- 

 ward, yet it is not in the same angle, the strata being more 

 inclined to the horizon than the line tracing the surface of 

 the promontory, a fact which I shall account for afterwards. 



From the Black Rock to the Giant's Causeway (about a 

 mile) the materials, and their arrangement, are similar to 

 those of the coast to the westward, viz. strata of table basalt, 

 generally separated by thinner strata of a reddish substance. 



At the Giant's Causeway a new arrangement commences, 

 one of the little systems I have mentioned in other memoirs, 

 • by the aggregate of which our coast is formed ; nature having 

 changed her materials, or their disposition, or both, every 

 two or three miles. To the system of strata comprehended 

 between the Giant's Causeway and Dunseverick I now limit 

 myself, as all the strata composing it emerge between these 

 two points. 



As we proceed along the coast from the Giant's Cause- 

 way eastward, we perceive the whole mass of strata ascend 

 gradually, culminate at the northern point of the promon- 

 tory, and then descend more rapidly, as the land falls away 

 to the south-east, until having traced them across the face 

 of the precipice we see them immerge separately at and be- 

 yond Portmoon Whyn Dykes. 



The western side of the promontory is cut down perpen- 

 dicularly, by eleven IVhyn Dykes ; the intervals between 

 them are unequal, but they all reach from the top of the 

 precipice to the water, out of which some of them again 

 emerge in considerable fragments ; they are all constructed 

 of horizontal prisms, which are strongly contrasted with the 

 vertical pillars of the strata through which they pass. 



One of the dykes at Port Cooan, on Bengore, half a mile 

 from the Giant's Causeway, is very beautiful; an insulated 

 rock about 16*0 feet high, and 20 in diameter, stands per- 

 pendicular in the middle of a small bay ; the main body of 

 the rock is similar to the contiguous consolidated masses ; 

 but on the east side a singular whyn dyke is joined to it, 

 composed (as they often are) of several walls agglutinated 

 together, with wall-like fragments of other parts of the dyke 



emerging 



