of glassy actynolite passing into hornblende, veins of quartz, magnetic and common iron pyrites. The basis sometimes approaches in its nature to clay-slate.
This aggregate rock composes the top of Clark's hill or Slieve-sleet, five hundred and forty-eight feet above Castlewellan. I also noticed it on Slieve Croob, between Slieve Nasky and Bakaderry town. I saw it again in loose blocks about Castlewellan.
A Druidical monument at Coagh near Cookstown, is partly made of an aggregate of crystals of hornblende. The same compound I observed, but not in situ, at the basis of the mountain of Coolcoserahan.
Felspar porphyry occurs in the county of Down, in the bed of the Finish, on the north-west side of Slieve Croob, near Drummara in the lower Iveagh; and in a decomposing state at Ballyroany, four or five English miles north-east of Rathfriland. In the first of these localities it is interposed in a compound rock of granular quartz and mica.
- the article on some porphyries of doubtful formation at the end of these extracts.