232 
Mr. Weaver on the 
and those of Portrane, with the additional interesting appearance 
of a stratified vein of sandstone conglomerate intersecting the 
former. 
§ 125. The coast on the south side of the Del van stream, which 
borders the county of Dublin, exhibits rocks, composed of vertical 
beds of fine grained greywacke, greywacke slate, and clay slate, in 
alternation with each other, similar to those which line a part of the 
eastern coast of Portrane. They range 20° south of east and north 
of west, and thin layers of calcareous spar, and contemporaneous 
veins of the same substance, are not unfrequent in these rocks. 
Following the coast, at low water, to the southward, repeat- 
ed alternations of compact greenstone and clay slate appear ; at 
first on the large scale, the beds of the former rock predominat- 
ing in width and frequency. These are succeeded by similar alter- 
nations, from two to three fathoms in thickness, and these again by 
others, from a few inches to two and three feet thick. These rocks 
range mostly north-east and south-west, dipping 53° to the south- 
east. The clay slate contains in several places thin layers of cal- 
careous spar. The greenstone abounds more or less in nuts, points, 
and contemporaneous veins of calcareous spar, the last being some- 
times more than two or three inches wide. This rock exhibits 
also at times numerous scales of silvery mica ; and sometimes it 
acquires a slaty structure and passes into clay slate. 
From hence to the rock on the western side of the quay at 
Balbriggan, we meet in succession with compact greenstone, granu- 
lar greenstone, or with greenstone passing into compact felspar, 
which acquires a slaty structure, much resembling some kinds 
of flinty slate. It ranges 20° east of north and west of south, and 
dips 30° toward the east. The rock at the quay is massy compact: 
greenstone,, 
