248 S. Hyde — Deep-mining in the South-west of Ireland. 



igneous rocks, through whose agency the mass of killas may have 

 been influenced, metamorphosed, and mineralized. 



We cannot agree with Professor Jukes {loc. cit. p. 28), who 

 believes that the " wide diffusion of copper ore in small quantities 

 over so large an area is against rather than in favour of the pro- 

 bability of rich mines being found." This really has no bearing 

 upon the question of " lode or vein" deposits and deep mining, 

 to be clearly distinguished from that of copper occurring in beds 

 of sandstone or shale, mechanically distributed through their 

 mass. We believe these mechanically deposited or amorphously 

 distributed cupriferous masses in the beds of killas and sandstone, 

 to be the source, through time and segregation, of the rich copper 

 ore in the lodes and veins now traversing the highly inclined and 

 contorted beds in which they occur — whether, as Professor Juices 

 supposes, the copper was derived from the " waste and destruction of 

 some original mineral vein district," and does not form here an 

 original mineral vein district itself, is a question which presupposes 

 the existence of older metalliferous rocks and lodes over the area 

 (but now no longer recognised), or rocks, the waste and result of 

 which is the present Old Eed Sandstone of the south-west of Ireland. 



West of Ballycummisk, and immediately east of Skull Harbour, is 

 situated Coosheen mine, where there appear to be no less than eleven 

 lodes, which some years since were proved and worked upon. All 

 these are east and west lodes, varying in their bearing or direction 

 from 10"^ east to 25'^ north. Seven of the eleven are copper-bearing, 

 containing either yellow, purple, and gray ore, or green carbonate, 

 and underlay or dip south. The sett is traversed from north to 

 south by a cross course or fault, accompanied by a parallel and well- 

 determined fl.ucan, which seems to have shifted the lodes. The 

 Killas to the south of the Coosheen dips north 40° to 60°, implying 

 that the mine is situated in a synclinal axis, parallel to the Bally- 

 dehob anticlinal, and may be the north dip to the north-west face of 

 the anticlinal, which runs south of Ballycummisk mine and through 

 Eossbrin cove. No less than five faults traverse the copper-bearing 

 zone of the Upper Old Eed Sandstone, between Cappagh mine on 

 the east, and Skull Harbour on the west, and the lodes of Bally- 

 cummisk and Coosheen are all more or less affected by them. 



It may be important to state that, at 42 fathoms from the surface, 

 and 16 fathoms below the deep adit, the No. 6 or old lode dipped south 

 6° in 1 (or 80'^), and contained a leader of 7 inches of solid gray 

 copper — the remaining 6 feet of the lode being composed of " quartz 

 gray copper, green carbonate, and blue peach." Even at the 

 limited depth or shallow working mentioned, upwards of £20,000 

 worth of copper ore has been returned. It is believed, from the 

 nature of the lodes, that Coosheen will be carried down to depths 

 equal to that of Ballycummisk, for it cannot be doubted but the 

 lodes of both setts are the same, and all are more or less parallel 

 to the strike of the Upper Old Eed beds ; and such appears to be the 

 law as regards the position and run of the lodes in the south-west of 

 Ireland. 



