Mr, Weaver on the Geological Relations of the South of Ireland. 33 



analogous to those occurring in the existing mine, been contained in the north ground, it must 

 have been detected either by the bore-holes distributed over that surface, or by the trenches. 



The preceding details, which may perhaps more immediately interest professed miners, are yet 

 important, since they establish the geological relations of this mine both in a positive and negative 

 manner; and they may thus prove useful to future inquirers in researches of a similar nature. 



During the course of operations between May 1827 and May 1829 inclusive, 15291 tons of ore 

 were raised, averaging in produce 13f per cent, of copper, the sale of which amounted to 18,090/. 

 18s. 9rf., being equal to 111. I6s. 6^d. per ton; the average standard price of copper during that 

 time having been about 108/. per ton. 



In the earlier part of this undertaking the ore raised, amounted sometimes to nearly 100 tons 

 per month ; but the last month's work yielded only 29 tons, the main deposits of ore having, in 

 fact, been worked out. These ores consisted chiefly of grey, yellow, and purple sulphurets. Green 

 and blue carbonates and tile copper ores, with small portions of native copper and crystallized red 

 copper ore, occurred much more rarely, having been chiefly found in the part of the blue lime- 

 stone immediately over the flat bed. Intermingled particles of galena were likewise incidentally 

 met with, as well as blende and iron pyrites more in mass. 



This remarkable metallic deposit, coeval in its origin with the limestone rock itself, must have 

 yielded, from first to last, a produce exceeding in value 100,000/. sterling. 



As dependent on the structure and condition of the limestone rock, I think it necessary to add a 

 few words on the water of this mine. When full access had been obtained to the interior, fissures 

 were found, in general nearly vertical, some upon a north and south, and others upon an east and 

 west range, which, in the course of their extent, varied from the tenth of an inch to four or five feet 

 in breadth, the expansions being sudden, irregular, and of comparatively short continuance. These 

 fissures and cavities are commonly filled with a closely compacted mass of pebbles, gravel, and sand, 

 imbedded in clay, and, when persistent, generally impervious to water; but unoccupied intervals 

 occurring in some places, it is easy to conceive that upon such fissures passing outwardly to the 

 lake, those spaces would become gradually enlarged by the fretting of the Jake water, and the 

 feeders of the mine be proportionately increased. Nor was this the only source of the water 

 flowing into the mine. From the horizontal disposition of the flat bed in its direction to the south- 

 ward, ascertained by the cutting of the deep level, it became evident that the flat bed must run into 

 the lake at the distance of about twenty fathoms from the embankment in the deep water, opposite 

 to Dyer's shaft, the bottom of the lake deepening in that quarter rapidly to the south*. And the 

 surge of the lake, which in a storm is like a tempestuous sea, could not but press its waters with 

 an increased impetus, fretting, by the line of the flat bed, into the mine. And such was found to 

 be the case in the progress of the deep level to the westward. 



Thus the discharge of water, from a depth of 9| fathoms, was, from May to December 1827, 3i 

 to 4 tons per minute ; and afterwards from a depth of 10| fathoms, between December 1827 and 

 April 1828, 4 to 5^ tons per minute, and in June 6} tons per minute ; but after the deep level had 

 passed Spillane's shaft, it increased progressively to 8, 9, 10, and 11^ tons per minute. This was 

 caused by the deep level cutting a vertical fissure four inches wide, and by the opening of the flat 

 space between the blue and siliceous limestone, to the height of nine inches. By the latter line 

 great quantities of pebbles were washed into the mine. As a check to the influx of water, dams 



* At the distance of 200 fathoms from the embankment, south of Dyer's shaft, the lake has, in 

 fact, acquired the depth of 35 fathoms, wiiich it retains to a considerable extent, the deepest point 

 being 40 fathoms, whence the bottom rises gradually to the opposite shore. 



VOL. V. — SECOND SERIES. F 



