327 



Pitchstone occurs at Sandy Braes, accompanied by Pearlstone. 



Phillipsite occurs in greyish, white translucent crystals at the 

 Causeway in small flesh-red crystals, with. Gmelinite, coating the 

 cavities of reddish-coloured earthy amygdaloid at Island Magee (see 

 Gmelinite), The Phillipsite here always forms the coating next the 

 matrix. 



Rhodolite is found associated with Chalasite and calcic carbonate, in 

 the cavities of amygdaloid, at Ballintoy, and at the Causeway. 



Quartz is got in Knocklayd Mountain, near Ballycastle ; at Divis, 

 near Belfast, in colourless crystals. At Dungiven was found a large 

 crystal, now in the possession of Mr. Ogilby, weighing nearly ninety 

 pounds. 



Pock Salt is found at Duncrue, near Carrickfergus (see p. 262). 



Soporite, or Soapstone. — A soft variety which hardens on exposure, 

 occurs in the amygdaloid rocks of Antrim, generally in nodules of a 

 grey, yellow, or brown colour. 



Specular Iron is got in the Isle of Magee, near Larne. 



Stillite occurs with Chahasite in geodes at the Causeway ; at Ballin- 

 toy, cream-coloured in sheaf-like aggregations, occasionally finely crys- 

 tallized with Seulandite ; at Portrush, aggregated white and globular ; 

 at Bengore Head, in small white crystals, with Apophyllite ; at Bruce's 

 Castle, Eathlin Island, in drusy cavities in greenstone ; at Dunluce 

 Castle. (See also under Apophyllite, Chahasite, Heulandite, and Lau- 

 monite.) 



Sulphate of Alumina occurs as an efflorescence in the lias shales at 

 Ballintoy. 



Talc is found near the Causeway ; near Dunluce Castle it is dendritic, 

 opal white, and pale green. 



Thomsonile, got occasionally near the Giant's Causeway ; at Island 

 Magee; at the Ball, in Eathlin Island, on transparent Analcime. 



Websterite occurs near Portrush, in thin seams and earthy in the 

 Assures of the greenstone on Calcite. 



Wollastonite of Thomson. Small tufts of this mineral have been 

 found at Portrush, accompanying Stillite in greenstone. 



XXXI. — On the Inscribed Cavern at Lough Nacloyduef, Parish oe 

 Bohoe, County oe Fermanagh. By "W. P. Wae^man, Esq. 



[Read May 25, 1868.] 



The lonely and picturesque "tarn" marked upon the Ordnance maps 

 as Lough Nacloy duff — the "Lake of the Bark Cavern or Digging" — 

 lies in the midst of a desolate, heath-clad highland, which extends 

 over a considerable portion of northern Fermanagh. In its immediate 

 neighbourhood, and for some miles around, there is no trace of cultiva- 

 tion, ancient or modern. All that meets the eye is heather, rock, and 

 bog, interspersed with irregular patches of rank grass, moss, or rushes. 



