287 
Geological Relations of the East of Ireland . 
oil the north-western side of the Coalbrook trough, we perceive a 
seam of coal about thirty-five yards below that of Coalbrook, being 
about twenty inches thick, and below this occurs another seam, 
about ten inches thick, at the distance of thirty yards. Beyond 
Copper trough, the seat grit rock rises up to the south-east in Glen- 
gall hill, about half a mile to the west of Ballingarry, under an angle 
of 12° 3 which position, as before observed, (§ 184) the grit, shale, and 
subjacent limestone preserve in this quarter. Hence no coal has 
been found to the south of the parallel of Glengall. 
§ 187. Two of these coal troughs sometimes conjoin in a part 
of their course; that is, the coal of one trough in ascending to the 
southward forms a continuous line with the coal of another trough 
ascending to the northward, so as to form a kind of saddle between 
them. This happens in the south-western part of the field of the Coal- 
brook and Canal troughs ; but in the north-eastern direction they se- 
parate again, each following its own course. The same appearance 
exists in the central part of the field, between the Canal and Clashdufie 
troughs, but they separate again, both toward the north-east and 
south-west, the seat rock coming to the surface in both these in- 
stances, as well as in the former. Such appearances seem to be 
owing, partly to the unequal elevation of the ridges of the seat grit 
rock, and the consequent unequal distribution of the coal beds over 
the surface of this rock ; and partly to the local fractures and denuda- 
tions, which the surface has undergone since the original formation 
of the coal tract : and viewed in this light, the Coalbrook, Canal, 
and Clashdufie beds may be considered as the same undulated series, 
partially broken and abrupted near the surface. 
§ 188. The Coalbrook, Canal, Clashdufie, and Copper troughs, 
are traversed by a slip, which ranges nearly north and south, and 
throws them down fourteen yards on the eastern side. A second. 
