154 
Mr. Weaver on the 
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clay slate, the western by mica slate, in parallel order, with the usual 
south-easterly dip ; but both to the north and south, the two slaty 
rocks coincide again, and conceal the subjacent granite. 
§ 37. Of the line of mica slate, which we have thus traced 
from Killiney Bay to Aghole mountain, it may be observed in 
general, that its breadth, both toward the northern and southern 
extremities, is very inconsiderable, and that in its widest part it no 
where exceeds three or four miles, as it soon graduates into clay slate* 
by which it is bounded for the greater part of its course. 
§ 38. Beside the minerals that have been incidentally noticed as 
occurring in this tract of mica slate, I have to mention hornblende, 
andalusite, hollow spar, garnet, and sphene. Hornblende, in crys- 
tals disseminated through this rock, is by no means uncommon 
throughout the district. ; and sometimes this mineral becomes so 
intimately mixed with the mica slate as to constitute a compact 
tenacious compound; as, for example, in Aghole mountain. Beds of 
common hornblende probably occur also occasionally in the mica 
slate, as detached blocks of that rock are sometimes to be seen ; for 
instance, in the northern part of Carrigacrow, and in the lower part 
ofBalreagh glen toward Glencree river. And, between Drumgoff 
and Fannanerin, a bed of hornblende slate was discovered by a trial 
level driven many years since. There are few parts of this tract 
also in which andalusite does not occasionally appear, and some- 
times also hollow spar, as in Croghan Moira. But garnet, which 
is in general so constant a companion of mica slate, is seldom to be 
observed. Of sphene, the only specimen that has occurred, was 
discovered lately by Dr. Taylor in mica slate, on the townland of 
Carriglinneen, adjoining to the military road leading to Drumgoff 
barracks. It was in thin flakes, interlaid between the laminae of the 
rock. 
