242 *S^. Hyde — Deep-mining in the South-west of Ireland. 



well-known Killas of Cornwall. It is this strip of country, with 

 its central ridge rising to 1,140 feet, (at Mount Gabriel 1,339), that 

 chiefly claims our attention, as being perhaps one of the most 

 important copper-bearing districts of the south of Ireland. Broad 

 transverse valleys cut this ridge in two or three places, the chief 

 and most important one being at Ballydehob, which gives rise to 

 the waters which pass into Eoaringwater Bay ; others to the north 

 and east, giving rise to the river lien, need not be mentioned ; neither 

 need we notice the parallel ridge to the north of the Mizen and 

 Ballydehob range, and which separates Dunmanus Bay from 

 Bantry Bay, although physically it is of high importance to the 

 question at issue. This narrow ridge and promontory attains an 

 elevation of 1,130 feet, several other points rising to 1,000 feet. 



The strike of these two parallel ridges and the three parallel 

 prolongations of the Carboniferous slate is about 25° north-east and 

 south-west or east, 25° north and west, 25° south. 



From Ballycummisk and Skull Harbour to Toormore Bay, and on 

 to the Mizen Head, a smaller ridge of land runs parallel to the main 

 axis, and it is in the east part of this range that the mines of Bally- 

 cummisk and Coosheen are situated. 



The Devonian (Killas) or Old Eed Sandstone, is without doubt 

 the oldest formation throughout the south-west of Ireland, and, 

 according to the maps of the Geological Survey of Ireland, and 

 the Memoirs accompanying them, written by the officers of the 

 Survey, it is divided into two groups (1) the " Old Eed Sandstone " 

 at the base, succeeded by (2) " the Upper Old Eed Sandstone " (or 

 Upper and Lower Old Eed), the latter is about 800 feet thick, and 

 near its lower boundary, according to the Geological Survey, occurs 

 the " Copper Zone," ^ and which would appear to " prevail through- 

 out the whole of the south-west of Ireland." 



The long peninsula of Glenarought and Slieve-Miskish, between 

 Bantry Bay and Kenmare river, the axis of which is composed of 

 Devonian Eocks, flanked by the Coomhola beds, contains the copper 

 mines of Bearhaven or Allihies. These very productive mines are 

 situated on low land, at the foot of the elevated Slieve-Miskish, 

 which abruptly rises 1,240 feet above the western ocean. The 

 western slope of this lofty and broken peninsula, and in which are 

 situated the Bearhaven mines, is composed of highly cleaved slaty 

 rocks or "Killas," interstratified with massive indurated and fine- 

 grained sandy beds, also highly cleaved ; the planes of cleavage being 

 north and nearly vertical, and striking north 33°-35°; many varieties 

 of the Killas, or clay slate occur, being grey, blue-grey, and buff in 

 colour, the latter being most noted for the presence of copper. 



The earliest known working in this Ballydonegan and Bearhaven 

 area was commenced about thirty years since in an east and west 

 vein or lode of quartz and copper pyrites, which was exposed in the 

 cliffs north of Ballydonegan bay, termed the Allihies old lode, and 

 which appears to have been worked some 50 or 60 fathoms deep. A 



1 Mem. Geol. Survey. Explanations of sheets 200-2-3-4-5, etc., County Cork. 



