Kinahan — The Economic Geology of Ireland. 353 



decay, leaving holes in the paths and crossings. Such unsound 

 corners result from the cutting of too large a flag or crossing-stone 

 out of a granite block, the outer part of which is weathered. The 

 effects of these rotten corners are conspicuous in many of the path- 

 ways and crossings. 



LEITRIM. 



Arigna Flags. — Recently a light railway has been constructed 

 to the collieries in this district, and it is now proposed to exten- 

 sively work the excellent coal-measure flags (vol. v., p. 679), 

 which formerly were very little utilized on account of the difficulty 

 of transport. 



MONAGHAN. 



Two and a-half miles S. W. of Smithborough there [is " an 

 evenly crystalline, dark-blue basalt dyke. Two other dykes occur 

 in the county E.N.E. of Castleblayney." (g. s. m.) 



In Lisserard, Knockaturley, and llamany there is a dyke of 

 green, mottled white, granitone, over a mile and a-half in length. 

 In the latter townland, about two miles from the Monaghan rail- 

 way station, the rock is exposed in a water-cut, and is found to be 

 a sound, good stone, which appears capable of being raised in good- 

 sized shapely blocks. A specimen was sent to Mr. Brindley, of 

 Westminster, who highly approved of it for polishing purposes. 

 It seems to be also well adapted for paving-setts. ( W. F. De V. Kane.) 



CO. WICKLOW. 



Aiighrim and Tinnakilly Granite Quarries. — The soda granites 

 (keratophyre) in these localities, as previously mentioned, are more 

 or less pyritous, and are supposed to be of Carboniferous or later 

 age. They occur as intrudes in the schists and in the older granite 

 (Haughton's Leinster type), having been probably " laccoliths," 

 their present appearance at the surface being due to denudation. 



Some of these rocks on weathering become clouded, or spotted 

 with rust ; but the better stones are only more or less speckled, 

 these different appearances being due to the varying amount of 

 iron present. From a careful examination of the place it would 

 appear that usually the laccoliths consist of irregular shells or 

 slightly-curved layers ; the outer shells as well as the adjoining 



SCIEN. PROC. R.D.S. — VOL. VI. PAKT VI. 2 E 



