380 



THE GEOLOGIST. 



coal, impure limestone, and sandstones called tlic " calp " scries, an 

 upper limestone, wliicli is overlaid^by a representative of the millstone- 

 grit, and coal-measure sandstones, and shales with some bad coal. 

 Thus we have as follows : — 



1. Coal-measure series. 



2. Millstone grit series. 



3. Upper limestone. 



4. Calp. 



5. Lower limestone. 



6. Carboniferous slates or shales. . 



7. Yellow, grey, or red sandstones. 



8. Sandstones and conglomerates. 



Tosslls also are not w^anting to determine the age of the lowest of 

 these rocks, the yellow and red sandstones having furnished shells of 

 the mountain-limestone, as the Productus and Orthis. 



The carboniferous slate and lower limestone may be studied in the 

 Dublin district, and the geologist should visit the carboniferous slate at 

 Poulscadden, near Howth, and also a section near the martello tower at 

 Portmarnock. The Old Eed Conglomerate may be seen at Shenick 

 Island, near Skerries, and the Posidonomya Becheri,'" a thin bivalve, 

 strongly marked, may be obtained in the black carboniferous shales of 

 Lough Shinny. We were informed by Mr. Kelly that, although he had 

 searched the carboniferous slates in above 150 localities in Ireland, he 

 had never found in them either the Posidonomya " or the " Peclen 

 2)apyraceusy^ and that these mollusks are, therefore, characteristic of 

 the shale beds ahove the slates. Eut, above all things, let us advise the 

 stranger geologist to apply to the gentlemen connected with the 

 Geological Survey and the Museum in St. Stephen's Green for infor- 

 mation as to route, &c., before he visits any locality. It will save much 

 time, trouble, and expense, and he will meet with true courtesy and 

 attention. 



Our route from Dublin to Dundalk lay through these carboniferous 

 deposits, with patches of lower limestone, which, off the Skerry Isles, 

 has been denuded from the Lower Silurian slates, and which, with the 

 exception of the Drogheda district, occupy the route from the Skerry 

 Ides, l y Dundalk, to JSTewbliss. Drogheda deserves a halt for the pur- 

 pose of studying the lower limestone and carboniferous slates. We 



