of the North of Ireland. 159 



coal formations, that supposing a line drawn across the Island in 

 the parallel of Lough Allen from east to west, the coal found to 

 the north of that line Is principally slate-coal, and that on the south 

 cannel coal. In one of the works, however, in Coal Island, a bed 

 of cannel coal six feet thick is said to have been wrought. 



The slate clay at Mary Ann Pit contains impressions of aquatic 

 pldnts, vegetable impressions similar to those of the Derbyshire 

 collieries have also been observed in the Ballycastle district. 



Clay ironstone occurs both in nodules and beds, and brown spar 

 passing into sparry iron ore has been observed at the coal works of 

 Ballycastle, where it forms a bed of some thickness traversing the 

 cliff at a little depth below the principal seam of coal. 



A bed of trap lying in a conformable position between the 

 strata of sand, occurs a little to the eastward of the coal works of 

 Ballycastle, between Fairhead and the little Glen of Port-na-crea, 

 along the Crag of Sron Gal or of the " White-nose." 



This geognostic fact, the only one of the kind I have seen or 

 heard of in the north of Ireland, was pointed out to me by the 

 ground bailiff of the collieries, who called it a horizontal dyke. 



Its thickness is about two feet. It has a slaty structure, and is 

 micaceous where it lies immediately in contact with the sandstone, 

 the usual characters of which appear altogether unaltered. It breaks 

 spontaneously into forms resembling triangular pyramids ; the tex- 

 ture Is remarkably close, it is almost entirely formed of finely 

 crystallized hornblende, with some thin scaly parts of white felspar : 

 it acts on the magnet, and yields a black enamel before the 

 blowpipe. 



* Several vertical dykes also occur trav-ersing the coal measures near Ballycastle, these 

 A^ill be particularly described in the accouut of sections on the coast- 



