122 PROCEEDINGS OF SOCIETIES. 



prosperity of Ireland. A square mile of coal, a yard thick, would yield 

 above three millions of cubic yards. 



At all events, the Slievebeagh district, being the geological conti- 

 nuation of the Glasgow valley, where thick and numerous beds of coal 

 are worked, and those beds repeated in the small but rich colliery at 

 Coal Island, in Tyrone, afford strong grounds to presume that there may 

 be coal here, though not yet discovered. Whether or not, Mr. Griffith's 

 opinion, as given above, and also at par. 9 of the quotations, emanating 

 from so high an authority, if allowed to go forward to posterity without 

 being contradicted or corrected, would be so far mischievous that it 

 would have the effect, in all future time, of preventing any proprietor 

 or geologist from even examining the district with a view to discover 

 coal. 



The Dublin calp district is the third in the list I have made ; but, 

 before entering into details regarding this, I shall make a few observa- 

 tions relating to the black shales which are associated with the Carbo- 

 niferous rocks. 



The Carboniferous Limestone of Ireland, in almost all places, has a 

 blackish, shaly band immediately under it, which has been called Car- 

 boniferous Slate. It has also a black shale over it, called millstone grit, 

 or the base of the coal shales. Those two black shales are different in 

 character, and require each a short description, because, in the Dublin 

 district especially, both of them occasionally take an important part in 

 the supposed calp. 



The lower shale, or Carboniferous Slate, consists of alternate beds of 

 black shale and dark-gray limestone, the shale prevailing towards the 

 base, and the limestone prevailing upwards, where the shaly beds 

 become mere thin partings between the limestone beds, and then dis- 

 appear altogether, the rock becoming a pure limestone. The limestone 

 beds of this group are generally of a dark-gray colour, composed often of 

 pure limestone, and filled with stems of Encrinites and other fossils. 

 This whole band is generally highly fossiliferous, having corals and shells 

 both in the limestone and in the shale or mud beds. This group is well 

 exposed about the Martello ToWer at Portmarnock, and thence along the 

 shore to Malahide ; also at Abbey Bay and Bundoran Bay, near Bally- 

 shannon, as already noticed, and many other places. This description 

 applies to the Carboniferous Slate almost everywhere. 



The upper shale, or that which overlies the limestone, is not like the 

 lower. Of this band there are three different types : one in the south of 

 Ireland, in Munster, and Leinster; a second in the middle district, lying 

 between Dublin and Galway, and a third in the north, in tho province 

 of Ulster. 



In the southern type the black shale lies directly and abruptly on 

 the gray limestone, without any passage from one into the other. It is 

 well seen at Old Leighlin, near Carlow ; at Abbeyleix ; near Cashel and 

 Killenaule, in Tipperary ; at Kilfenora, in Clare ; at Ballybunnion, in 

 Kerry ; at Foynes, in Limerick ; and between Buttevant and Mallow, 

 in Cork. 



