74 Mr. Bryce on the Geological Structure of 



(10.) Mr. Conybeare noticed abed of clay porphyry on the west side of 

 Fairhead, under the level of the coal formation ; it is probably contained in 

 the old red sandstone mentioned as occurring there. If so^ the analogy be- 

 tween its position and that of the Cushendall porphyry is striking and illustra- 

 tive. The rock in both localities would thus be contained in the old red 

 sandstone, and the new conglomerate which covers the porphyry at Cushen- 

 dall overlies the coal formation in Murlogh Bay. (See after, art. 16.) 



Other points, near Cushendun, at which porphyry occurs, are noticed in the 

 map. 



Carboniferous Limestone. 



(11.) This rock is fully described by Dr. Berger. It appears on the shore 

 near the Collieries, under the coal-field ; but is of very small extent, and does 

 not occur in any other part of the district. 



Coal Formation. 



(12.) The coal measures exhibit the usual alternations of coal, sandstone, 

 slate clay, and bituminous shale. To the accounts of it by various authors, I 

 shall add only a few observations on its superficial extent. 



It has been stated, (p. 72) that the formation reposes at its northern ex- 

 tremity upon the carboniferous limestone, underlaid by old red sandstone ; on 

 its southern boundary it rests immediately on mica slate'. 



The sea is the northern boundary of the coal-field from Ballycastle on the west to the south-east 

 corner of Murlogh Bay on the east ; its southern boundary almost coincides with the Carey river 

 from Ballycastle to the townland of Drumnakeel, where that river turns westward into the valley 

 before mentioned. Here its boundary turns north-east and passing through Drumadoon, ranges 

 by the trap of Fairhead ; and then extends eastward in a narrow zone between the trap and the 

 mica slate, and, passing afterwards under the chalk, finally expands into a deposit of considerable 

 importance in Murlogh Bay. 



The coal strata thus emerge on all sides from beneath the basaltic mass 

 of Fair Head, which is by this means isolated. The usual alternations of 

 sand-stone with slate clay and bituminous shale appear in many places; 

 but are exhibited beautifully in a section on the banks of the Carey river. 



(13.) In Murlogh Bay the beds are precisely similar to those in other parts 

 of the field. A sandstone cementing small quartz pebbles occupies the shore, 

 and is well seen near the great dyke. Mr. Conybeare thinks it identical with 



' See particularly the very valuable " Geological and Mining Survey of the Antrim Coal Di- 

 strict," by Richard Griffiths, Esq. ; in which an accurate account is given of the various beds of 

 this formation. 



