GEOLOGICAL SOCIETY OP DUBLIN. 137 



to the Millstone Grit series ; descending to the westward, we lose the 

 Millstone Grit, and the Upper Limestone appears again at the surface in 

 the line of section ; and further west we find the calp and shale cropping 

 out from beneath it, and forming the valley of Swanlinbar, which is alto- 

 gether composed of the Calp series ; from whence it extends northward 

 to Florence-court, where it terminates, and the subjacent Lower Lime- 

 stone commences, and continues to Enniskillen. In a south-western 

 direction from Swanlinbar the Calp extends to Ballinamore, in the county 

 of Leitrim, where we again find the Lower Limestone cropping out from 

 beneath it. 



Here let us pause to consider the result of what has been shown. 

 We find that to the east of Slieve Eushen the Calp series rests on the 

 Lower Limestone at Drummany, and is covered by the Upper Limestone 

 at Ballyconnell ; again, in a north and south direction, at right angles to 

 the section, we find that the Lower Limestone, extending southward 

 from Enniskillen, is covered by calp and shale near Florence- court, from 

 whence it continues, in a southward direction, to Ballinamore, where it 

 rests on the Lower Limestone of the valley of Leitrim. In fact, the 

 Upper Limestone of Slieve Eushen is entirely surrounded by the Calp 

 series, which is itself surrounded by subjacent Lower Limestone, for a 

 circumference of thirty-six miles : and thus in this case we have a suc- 

 cession of concentric circles, each surrounding the other, in an ascending 

 order from the Lower Limestone by the Calp to the Upper Limestone, 

 proving the triple subdivision of the Carboniferous Limestone System, as 

 originally described by me, to be correct ; and consequently Mr. Kelly's 

 view that the Carboniferous Limestone of Ireland consists of one undivided 

 series, based as it is on the occurrence of supposed faults, is erroneous 

 and untenable. Continuing the section westward, the Calp of the valley 

 of Swanlinbar is succeeded by the Upper Limestone of Cuilcagh moun- 

 tain, which, as at Slieve Eushen, is capped by the Millstone Grit ; and, 

 still proceeding westward, the same series crosses the valley of Lough 

 Allen by the source of the Shannon, and thence by Lugnaquilla and 

 Lackagh mountains, each of which contains a bed of coal near the summit. 

 To the west of Lackagh mountain the Upper Limestone crops out from 

 beneath the Millstone Grit, and descends into the valley of Manorhamilton, 

 where the Calp series is again well exposed, as well as a portion of the 

 Lower Limestone, the remainder having been cut off by the protrusion 

 of the granite ridge of Benbo mountain, but which, in continuation in a 

 south-western direction, extends to Collooney, &c, in the county of 

 Sligo, where it is fully developed. 



To the westward of the Benbo ridge we have again the Upper Lime- 

 stone, and beneath it, in the remarkable valley of Glencar, there is a fine 

 exhibition of the calp and calp shale, which on the west side is again 

 succeeded by the Upper (or splintery) Limestone of Benbulben. This 

 rock forms the upper portion of this lofty mountain, the table summit of 

 which is characteristic of the district. 



Descending westward from Benbulben, we find the strata beneath the 

 Upper Limestone to consist — first, of a series of beds of calp and shale, 



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