2m 
Geological Relations of the East of Ireland \ 
the north-east ; and in traversing the limestone and slate clay it 
produces an obvious derangement, the beds on the northern side of 
the vein being horizontally disposed, while those oil the south 
form a declining curve. The composition of this vein is perfectly 
similar to that already noticed; (§ 159.) and the white base of cal- 
careous spar is strongly contrasted with the fragments of limestone 
and slate clay, some of which are even two feet and a half in length, 
and one foot in breadth ; (see Plate 13. fig. 12.) 
North of this vein the beds are traversed by four small parallel 
veins of calcareous spar, which do not produce any derangement : 
and a little farther north, we encounter another breccia vein, pre- 
serving the same north-west range and north-east dip, and com- 
posed chiefly of calcareous spar, containing some fragments of lime- 
stone and slate clay. This last vein no where exceeds six inches 
in width, and it is gradually reduced in both extremities to a mere 
fissure, the filled vein not being traceable for more than twenty feet 
in length. 
It is impossible to contemplate these and analogous phenomena 
(§ 95.) without believing that one class of veins, at least, have ori- 
ginated in open fissures, which have been subsequently filled in part 
from above. 
§ 161. To the south of Drummahaugh headland, the beds of 
limestone and slate clay acquire a nearly vertical position, but they 
subsequently subside into an angle of 40° toward the south ; and 
this disposition is preserved in the north side of Rush bay, where 
the limestone rock presents one clean uninterrupted sheet for about 
two hundred yards in length. Alluvial matter now occupies the 
beach to the town of Rush. 
§ 162. On the south side of the bay of Rush, and east of the 
