GEOLOGICAL SOCIETY OF DUBLIN. 225 



On the whole, Arklow Rock consisting of Hills Big and Little, pre- 

 sents a fine example of an igneous protrusion, or perhaps succession of 

 protrusions through the slate rocks ; and the frequent variation in the 

 structure and composition of the rock in different parts proves that 

 similar rocks which occur in various parts of Wicklow and Wexford, 

 intermixed with slate rock, are also igneous protrusions, though in 

 many cases, owing to their ambiguous character and schistose structure, 

 I have classed them with, and called them, metamorphic slates. 



The quarry at Gorey may he instanced as an example, also Ask Hill, 

 north of Gorey, where the porphyry and felspathic rocks are associated 

 with greenstone, similar to that on Rock Little. 



On the whole, the results of the examination of Arklow Rock leave 

 no doubt on my mind as to the igneous origin of Tara Hill, and other 

 hills and ridges of that district ; but still there are several localities in 

 which both porphyritic and felspathic rocks occur, so intimately associ- 

 ated with rock presenting a schistose structure as to render it doubtful 

 whether they should be classed with igneous or with schistose meta- 

 morphic rocks, and I may mention Rennogue Hill, near Gorey, as an 

 example. 



Me. Joseph Kincaid, Jun., exhibited, and read the following remarks 

 on, — 



A SECTION ACROSS THE COAL BEDS OF LEITBIM. 



The paper which I have the honour to lay before the Society has refe- 

 rence to a section made through the Coal district of the county of Leitrim. 

 It was taken in a direction nearly north and south across Lough Allen. 

 The beds south of that Lake are almost horizontal, and north dip about 

 10°. Starting from the hills above the Creaghan Company's Iron Works, 

 near the small Lake Lackagh, we pass over the red and white sandstone, 

 or greenstone, in which occur thin seams of coal. These were formerly 

 worked, but have been abandoned for some time. Descending then by 

 the river that runs by the Company's furnaces, we have exposed a thick 

 bed of shale, in which are the workings for ironstone. This is found in 

 balls, and in the bed, the former uppermost, about five or six feet thick, 

 and of great richness, and the latter immediately below, not so rich, but 

 also very valuable. Beneath this, at the furnaces, occurs a seam of ex- 

 cellent fire-clay, which lies at the bottom of the shale. It is from eigh- 

 teen inches to five feet thick, and the specimens of alum are from this 

 seam. I also found some well-preserved Orthoceratites in the limestone 

 nodules that surrounded this. These nodules are formed of thin coats 

 or layers, and are generally of large size ; but those I was able to split 

 open generally contained these fossils. Below this occurs an impure 

 limestone, called Calp, — this being, I suppose, a mere lithological dis- 

 tinction. In this I found many traces of Posidonomya. 



Further to the west we come upon the limestone that is worked for 

 the Company's furnaces. This is very hard and compact, and contains 

 few fossils. I was only able to obtain a few small specimens of 

 Atrypa. 



