GEOLOGICAL SOCIETY OF DUBLIN. Ill 



not in the middle or the north. The Upper Limestone is the upper part 

 of the Limestone, the whole of it being one mass, and undivided, with 

 only trifling exceptions, which I shall particularize ; and the millstone 

 grit is the base of the Coal-rocks. 



It is remarkable that the Carboniferous Slate, that is, a slaty band, 

 which lies between the Old Eed Sandstone and the Limestone, has not 

 been noticed at all in this " Outline." Dr. Griffith subsequently intro- 

 duced this member into his classification, as shown upon his recent Map, 

 and it is a good and true member. It is well developed on the shore at 

 Poulscadden, near Howth, about Portmarnock Martello Tower, and 

 thence to Malahide in the county of Dublin, and a hundred other places. 



At par. No. 2 the Carboniferous Limestone has been divided into 

 four parts : — 



1. Yellow Sandstone, which is stated, at page 9 of the " Outline,' ' 

 to be 600 to 1000 feet in thickness. 



2. Lower Limestone ; thickness not given. 



3. Calp, alternating with black shale and sandstone, which is stated, 

 at par. 5, to be, at Bundoran, 1700 feet in thickness. 



4. Upper Limestone, which at par. 9 is given as 500 to 650 feet 

 thick. 



Besides the Yellow Sandstone, which may be the subject of a future 

 paper in this Society, there are three other divisions made of the lime- 

 stone in this passage of the " Outline," of which the middle one is the 

 Calp, which is further described at par. 7. 



There are four large calp districts in Ireland, shown on the latest 

 issue of Mr. Griffith's " Geological Map." 



1. The Bundoran district, which occupies parts of the counties of Fer- 

 managh, Leitrim, and Sligo. It extends from Lough Erne to Bundoran, 

 and thence along the sea-shore to Grange in Sligo. This district 

 occupies about seventy -five square miles. 



2. The Slievebeagh district, which lies between Lough Neagh and 

 Lough Erne, extending from Dungannon to Brookborough, thirty miles, 

 and about eight miles wide, or 240 square miles. 



3. The Dublin district, which occupies a great part of the counties 

 of Dublin, Meath, and Westmeath, comprising more than 1000 square 

 miles. 



4. The Galway district, which lies chiefly between Banagher and 

 Athenry, above 450 square miles. 



I shall make observations on each of those districts, beginning with 

 that of Bundoran. 



Bundoran is situated on the south coast of Donegal Bay, about three 

 miles to the west of Ballyshannon. It will be seen by a glance at the 

 " Geological Map of Ireland," that, a few miles inland from the northern 

 shore of Donegal Bay, there is a broad, well-developed band of Old Bed 

 Sandstone, extending fromDunkineely to Lough Esk, crosses the London- 

 derry road three miles east of the town of Donegal, and continues for three 

 miles south of it, where it ends abruptly, apparently cut off by a fault. 

 Three miles farther on, and a mile east of the village of Laghy, it appears 



