157 
Geological Relations of the East of Ireland. 
abruptly cut off by a vein of granite, from four to eight inches 
wide, ranging 25° north of west and south of east, and traversing 
the mica slate, but not producing any displacement of its strata. 
As this vein in its direction crosses the ravine, its limits are not 
within view. 
About twenty yards higher up, we perceive a bed of compact 
greenstone porphyry in the mica slate, from four to five feet wide ; 
and lower down in the ravine is a similar bed about two feet wide. 
A little higher up, a ravine comes in from the north, crossing the 
mica slate, which ranges here 1 5° north of east and south of west, 
and dips 52° toward the north-west ; and beyond this, the firm rock 
soon becomes concealed by loose fragments in the brook and soil 
in the banks. 
Mica slate occupies but a small portion of the northern face of 
Seefiniane adjacent to the ravine ; but this face is strewed with 
numerous loose stones of mica slate containing schorl ; and also of 
quartz associated with slender prisms of schorl, and sometimes also 
with felspar, the three forming a coarse granular compound ; but 
in general the quartz predominates. These fragments are no 
doubt derived from beds in the mica slate ; for lower down a bed 
of this kind crops out near the ravine, distinctly ranging and 
dipping with the slaty rock : it is about six inches wide. In the 
ravine itself the mica slate also appears sometimes intimately- 
associated with schorl ; and the loose fragments on the northern 
brow frequently exhibit crystals of andalusite ; a mineral of com- 
mon occurrence in other portions of the mica slate tract. Some 
of the beds of granite in the ravine contain minute crystals of 
garnet. 
§ 41 . The relations of the granite and mica slate are also partly 
disclosed in the ravine on the south side of the hollow above 
