114 PROCEEDINGS OF SOCIETIES. 



them is red sandstone ; another is black shale, of the Coal series ; a 

 third, yellow magnesian limestone ; a fourth, thin beds of red compact 

 limestone, interstratified with red sandstone and red shale ; a fifth, 

 red sandstone again, and so on. Each compartment between the dykes 

 is, say, a block of rock. Some of those have been pushed up, some let 

 down, and, as the strata are nearly level, what was once one continued 

 bed is now broken up, and in position on different levels between the 

 dykes. The surface of the whole group was afterwards worn down to 

 one general plane by denudation. In such a locality a man, stepping 

 across one of the whin-dykes, may get on higher or lower strata by 20, 

 50, or 100 feet, at one side of the dyke than on the other. 



2. My second objection to this classification is this — 



The succession at Bally shannon begins with the Lower Limestone, and 

 is in ascending order, as described in quotation No. 7. This section I 

 interpret in another way. Instead of an ascending succession, I take it 

 to be that the case is reversed, and that, proceeding from Ballyshannon 

 to Bundoran, the geologist, travelling over the strata westwards, is de- 

 scending, instead of ascending, in the series. The black shales and 

 interlaminated limestones, both in Abbey Bay, near Ballyshannon, and 

 Bundoran Bay, contain a profusion of those fossils, both shells and corals, 

 which abound in the Carboniferous Limestone ; and the whole character 

 of this band — limestones, shales, and fossils — accords with the Carboni- 

 ferous Slate of other places, or that band which lies next below the Car- 

 boniferous Limestone almost everywhere in Ireland, and is especially 

 similar in character to the Carboniferous Slate, where the succession 

 admits of no doubt, about Bruckless and Dunkineely, north of Donegal 

 Bay, and in three or four places on the coast of Sligo and Mayo, Where 

 Old Bed Sandstone, Carboniferous Slate, and Limestone are all clearly 

 visible in succession. 



I shall more particularly point out a means of identifying this fossili- 

 ferous shale and limestone group when I come to discuss two black shale 

 bands in the Dublin district, the upper one of which, called the Calp 

 of Dublin, is almost destitute of fossils, and such as it does contain are 

 peculiar to itself. 



The description of the second member of this succession appears to 

 me to be inaccurate, as if it had been copied from some wrong page of a 

 note-book by mistake. Balls of clay-ironstone have been described in 

 it. In searching for the fossils of the Carboniferous Limestone I exa- 

 mined carefully the cliffs and the northern shore of the river Erne, from 

 Ballyshannon downwards towards the sea, at low water. I also exa- 

 mined in Bundoran Bay almost every bed of rock. The black shale, 

 interstratified with impure argillaceous limestone, is tljere ; but I saw 

 neither beds nor balls of clay-ironstone. Beds and balls of clay-ironstone 

 are usually met with in the coal- shales, and not elsewhere. They abound 

 in the millstone grit district between Pettigo and Drumquin, and in all 

 the coal- shales round Lough Allen ; but they do not occur in any Car- 

 boniferous Slate that I know. This division is well developed on the 

 sea-shore between Portmarnock and Malahide, in the county of Dublin, 



