217 
Geological Relations of the East of Ireland. 
they seldom continue productive for more than thirty fathoms in 
length. There are several small ones of this description in the upper 
mine ; and in the lower mine there are six in the vicinity of the Copse 
and Boundary shafts, and two in that of the Farmer’s shaft. These 
have yielded considerable quantities of valuable ore. 
§ 113. In the course of the operations attending the driving 
of levels and sinking of shafts in Cronebane and Tigrony, I have 
observed that the slaty rocks, (whose general range is nearly north- 
east and south-west, and dip south-east at an angle of 65°) are 
divided into great beds, commonly about five fathoms thick, by 
parallel seams or joints, which intersect the inclined plane of the 
clay slate at right angles, dipping 25° toward the north-west. These 
seams are open fissures, which sometimes will admit one or two 
fingers, and at other times scarcely the blade of a knife. In their 
progress they pass uninterruptedly through all the beds and con- 
temporaneous veins included in the slaty rocks, dividing them, and 
sometimes producing, as it were, a sensible alteration in their disposi- 
tion, though to no great extent. This tendency toward a division 
into horizontal beds, (independent of the slaty structure) may also 
be observed in several parts of this district, where the rock has been 
partly exposed to observation ; as for instance, in the line of the 
new mail-coach road, in constructing which several rocks have been 
cut into at a great expense. 
§ 114. In the twelve years, ending 1799, the mines of Crone- 
bane had yielded 7 533 tons of ore, which produced on an ave- 
rage 84 -f- per cent, equal to 670 tons, 11 cwt. of copper: a duty of 
sixteen shillings and sixpence British per ton having existed up to 
this period on the importation of Irish ores into Great Britain. 
In the next twelve years, ending 1811, the produce was 19,342 
tons, 13 cwt. of ore, yielding 5 T S T per cent, equal to 1046 tons, 10 
Vol. V. 2 E 
