253 ON THE BASALTIC COUNTRY IN IRELAND. 



Additional oi- rangcment of their strata, will throw any light upon the 



ffi&L 8ub -i cct - 



mocks. When we examine the assemblage of hummocks above 



Knockmull, that is, Sconce, Fermoyle, and Altabiian, we 

 find their materials and stratification precisely similar to 

 that of the country below them to the eastward, where the 

 abruptions of the strata ara displayed in long stony ridges ; 

 to the south, the abruptions on the summit of Kcady moun- 

 tain discover the same similarity ; and to the north-west the 

 grand facade of Magilligan Rock, three miles distant, dis- 

 plays an accumulation of exactly the same sort of strata 

 consolidated into an enormous mass. 



The hummock of Dunmull is formed of two very parti- 

 cular strata, a columnar, and an irregular prismatic; but I 

 showed you, a mile to the northward, at the facades and 

 quarries of Islamore and Craigahuller, at the base of the 

 hill, that the whole ridge, on the summit of which Dunmull 

 is placed, was a consolidated mass, formed by alternate 

 strata of the same'description : and that the arrangement of 

 the whole country below, and adjacent, was precisely the 

 same with that of the hummock of Clogher, I proved to 

 you at the curious opening of the strata at Bushmills 

 Bridge, and in the facades at the Gianfs Causeway. 



After these proofs, that so many (and I might proceed to 

 the rest) of our detached hummocks are in their construc- 

 tion and materials similar to, and connected with, the main 

 consolidated masses of which our country is formed, I 

 think it will scarcely be asserted, that these hummocks 

 were originally formed solitary and separate as they now 

 stand ; but rather that they were once parts of that vast 

 whole, and left behind at their present form, upon the re- 

 moval of the contiguous portions of their strata by some 

 powerful agent, of whose operations and modes of acting 

 we have hitherto obtained little knowledge. 



o 



The highest point on the facade of Cave Hill is called 

 M'Art's Castle, and appears to be a solitary fragment of a 

 stratum, precisely similar to those below it, and obviously 

 once extended like them. 



The inegularity of the summit of Fairhead plainly 

 shows, that iu gigantic column* once reached higher. 



And 



