262 
Mr. Weaver on the 
calcareous spar. The limestone is succeeded in the north-western 
angle of Loughshinny bay by a body of black slate clay, about 
forty fathoms wide, resting in the first instance conformably on the 
limestone, but subsequently exhibiting most singular inflections and 
contortions. This slate clay consists of thin layers, alternately hard 
and soft, and it abounds in pyritous particles ; whence it is ex- 
tremely subject to decomposition, forming alum and sulphate of 
iron. Limestone now appears resting on the thick bed of slate 
clay, and dipping 45° south. It forms strata from three inches to 
two feet thick, frequently alternating with slate clay. The lime- 
stone is here also curiously interwoven with contemporaneous 
veins of calcareous spar, sometimes in a kind of net work ; which, 
however, are confined in every instance to a single stratum. Re- 
peated inflections of these beds now take place, rising under an 
angle of 65° to 70° on the north side ; but on the south side, sweep- 
ing off at an angle of 30° to 35° with the horizon. 
§ 160. Analogous, yet gentle undulations in the beds of lime- 
stone and slate clay are repeated throughout Drummahaugh head- 
land, which forms the southern side of Loughshinny bay, and is 
the site of an ancient Danish encampment. These inflections may 
be compared to the gentle swells of the sea, the ridges sometimes 
ascending in their upper part into the pointed form. But these 
rocks, which are well exposed in the cliffs on the north, the east, 
and the south sides of the promontory, preserve in general a range 
from east to west, with a dip toward the south. In the eastern 
face of this headland some interesting facts are also exhibited ; a 
second breccia vein being visible, both in a vertical and horizontal 
section of the cliff. On the beach it is four feet wide, but in 
ascending the cliff it diminishes to about one foot and a half in 
width. It ranges also north-west and south-east, and dips 80° to 
