Geological Relations of the East of Ireland . 173 
No. Fathom 
10. Clay slate, greenstone, and greenstone slate, in alternation ... 20 
11. Ash-grey clay slate, with some small beds of greenstone and green- 
stone slate toward the latter part . . . . Ill 
12. Ash-grey clay slate 88 
13. Greenstone and greenstone slate, constituting the body of the hill 
at its junction with the northern arm, and ranging to the north- 
east through a considerable part of that arm. 
This greenstone examined by the lens is seen to consist of mi- 
nute crystals of yellowish grey felspar, intimately mixed with spots 
of black hornblende ; its aspect to the naked eye being greenish or 
bluish grey, with a compact small grained uneven fracture. The 
compact greenstone is slaty in the great, but when approaching to- 
ward or in the vicinity of clay slate, it acquires a fissile texture. 
These rocks are succeeded to the eastward by yellowish clay 
slate ; which graduates into bluish grey clay slate, containing many 
cubical and some few dodecahedral crystals of iron pyrites, and tra- 
versed by numerous contemporaneous veins of quartz, both barren 
and metalliferous, which are frequently intermingled with chlorite. 
The general range of all these rocks approaches to the north-east 
and south-west, with a dip to the south-east of 70° to 80°. But a 
local exception occurs in the two serrated peaks of this mountain ; 
where the clay slate ranges 10° south of east and north of west, 
dipping in the northern peak 41°, and in the southern 38° toward 
the south. 
§ 64. If we farther examine the line of the two Avons, of the 
Daragh and Ovoca rivers, we find the clay slate tract exhibiting some 
other relations worthy of attention. 
In Ballygannon wood, on the right bank of the Avonmore north- 
west of Rathdrum, are two beds in the clay slate, about a furlong 
distant from each other, composed of granular felspar, and some 
