Mr. Weaver on the Geological Relations of the South of Ireland. 31 



To redeem this mine I devised the following plan : 1. To form an efficient embankment, drawn 

 from the west to the east through the deep water on the south, thus gaining a considerable portion 

 of land from the lake : 2. To sink a new engine- shaft south of the old mine, intercepting in greater 

 depth the metalliferous bearing, and forming there new workings : 3. To drain, in the mean while, 

 the old mine by horizontal rods extending from the new engine-house to the old engine-shaft : 

 4. and lastly, By connecting the new with the old workings, to render the new engine-shaft the 

 central point of drainage. 



The preliminary works having been completed in sixteen months, the drainage was effected in 

 May 1827. The succeeding operations showed that the real geolpgical circumstances of this 

 mine had never been clearly understood. They proved, in fact, that the mine was not wrought 

 upon a metalliferous bed, nor upon any real rake vein or true lode ; but that the metallic deposits 

 formed a portion of, and were contemporaneous with the rock mass itself; being most unequally 

 and irregularly distributed in the form of isolated portions, branches, strings, and particles of ore 

 minutely disseminated, in a manner quite analogous to the strings, filaments, and other portions of 

 calcareous spar which are also embodied in the substance of the limestone mass. Though thus irre- 

 gularly incorporated with the rock, the general disposition of the metalliferous ground assumed an 

 east and west range with a southerly dip, but without any wall or decided line of partition, so that 

 the form of the excavation, made in any case, depended wholly on the extent to which the ore 

 was disseminated, laterally as well as longitudinally, and deserved extraction. 



In the plan the shaded space indicates the extent of the excavations upon ground productive of 

 ore, its northern extremity showing the actual outcrop at the surface upon an inflected line from 

 east to west, and its southern extremity denoting the irregular limits of the metallic deposits in 

 their inclination to the southward. The dip of the excavations thus formed, is exhibited in the 

 section. The northern (ore-ground) inclines in general at an angle of 1 G" from the horizon, and 

 the southern (ore-ground) at an angle of SB'' ; but to the westward they collapse, run together, and 

 are finally attenuated in the form of a thin wedge. On the other hand, to the eastward, the southern 

 body of ore-ground extends only a short distance beyond the meridian of the New Engine Shaft, 

 while the northern body becomes in the eastern direction gradually more and more contracted in its 

 dimensions, terminating, beyond the excavation called the Blue Hole, in occasional slight fila- 

 ments and particles of ore, dispersed through the rock, unworthy of pursuit. The workings in 

 the Blue Hole itself were conducted in the northern part on discontinuous branches and strings 

 of yellow copper ore ; and in the southern part chiefly on irregular masses imbedded in the 

 rock, which consisted of an unprofitable compound of blende, galena, and iron pyrites, with a 

 slight intermixture of copper ore. Yet considerably to the westward, adjacent to the Cliff 

 shaft, an isolated, profitable bearing of good yellow ore was met with, but this did not ascend to 

 the surface. 



In short, Ross Island consists for the greater part of what may briefly be 

 called the siliceous limestone, namely, a series of thin, alternating- beds of lime- 

 stone, hornstone, quartz, and lydian stone, with some few of clay-slate inter- 

 posed. This series supports, at the southern angle of the isle, continuous, thick 

 strata of blue limestone, which form a body, in its highest part, from ten to 

 twelve fathoms in thickness, and, in its lowest part, about six fathoms. The 

 blue limestone rests in a perfectly conformable position upon the siliceous lime- 

 stone, the inflection of the two kinds of rock corresponding throughout, rising 



