the Counties of Mayo and Sligo in Ireland. 



165 



the beds beneath remain horizontal. This derangement, therefore, can have resulted only from a 

 lateral pressure forcing the layers of stone horizontally, but acting superficially. Such is the ap- 

 pearance exhibited in the hill north of Poolaclogher, on the east of Kilcummin headland, especially 

 at a point near the landing place, represented in the accompanying wood-cut, No. 4. 



No. 4. 



Contorted strata of shale and grit north of Poolaclogher. 



At Poolaheny, on the east side of Killalla Bay, the course of this dyke is often obscured by the 

 drifting of a shingle-beach, but it is found to the east of the mouth of the Dromore River, on the 

 coast of Tyreragh, preserving the same characters, and influencing the adjacent rock in the same 

 manner. Thence, holding its direct course to the south-west of Aghris Head, and rising from the 

 water through the beds of rock covered at high tide, it is seen for about 200 yards, but on reaching 

 the shore, the sand banks and soil prevent further observation ; and the dyke is concealed to the 

 picturesque chasm, called the Glen, produced by it in the side of Knock-na-Ree. 



The soil and the fallen rocks which have been thrown together and levelled to form a walk 

 through " the Glen," obscure the trap except at a few points, where it may be examined satisfac- 

 torily. To judge from the present appearance of the rift, it was never filled to the brink with trap; 

 as the sides would close together with scarcely any void, the projections of one face coinciding ac- 

 curately with the recesses of the other. I have next observed this dyke below the village of 



