GEOLOGICAL SOCIETY OF DUBLIN. 113 



in quotation No. 2, attributable to a great fault that exists in the vici- 

 nity of Lough Erne and Bundoran, and not that there are two separate 

 bands of limestone. 



First. Immediately to the west of Bundoran, on the shore, there is 

 a ravine, several yards long and a few feet wide, with perpendicular faces, 

 worn out by the action of the tide. A man can go through this ravine 

 at low water, and lay his hand, on the north side of it, on sandstone 

 rOck ; and, on the same level, on the south side, he has the black shale 

 and limestone of Bundoran Bay (see Plate VI., Tig. 1). The ravine ap- 

 pears to be on a perpendicular fault, in which the one rock is thrown up 

 to the surface, or the other let down, so as to be brought into juxta- 

 position with each other. 



There is another, a clear case of a similar fault on the north side of 

 Ballyshannon Harbour, at Kildoney, between two groups of rock sand- 

 stone and limestone, the beds of both being nearly level, as at Bundoran. 

 By this fault they are brought into juxtaposition with each other. There 

 is no trace of superposition, but only simple contact. The whitish sand- 

 stone at Kildoney Point, and that at Bundoran, are both insulated ; and 

 this circumstance, with the faults, renders positive proof of sedimentary 

 succession at the junction unattainable. Here, however, are two rocks 

 of different kinds in contact: sandstone and limestone at Kildoney; 

 sandstone and black shale at Bundoran ; not one over the other, but 

 one beside the other, separated by a vertical fault ; clearly showing the 

 one thrown up, or the other down from its original position (see Plate 

 VI., Fig. 2). Under such circumstances, it is no great wonder that a 

 mistake might be made by a hurried observer who travelled over the 

 country from Ballyshannon to Bundoran, and that he adopted the geo- 

 graphical instead of the geological succession. 



I believe similar cases to be numerous in the neighbourhood. The 

 country about Ballyshannon, and the valley of Lough Erne, is beset 

 with faults : some of them are of unusual magnitude, to one of which 

 I shall allude presently. 



I consider it more rational to suppose that those sandstones are the 

 top of the Old Bed, which we know exists a short way below, and 

 which have been moved relatively upwards out of their original position 

 by means of faults, than to imagine them, and call them calp sand- 

 stones, slipped down from a higher place, and resting in juxtaposition 

 with the limestone at Kildoney, or the black shale at Bundoran ; this 

 calp sandstone being a rock which was not known in any part of the 

 world before this idea was suggested to Mr. Griffith's mind. 



As at Ballyshannon, so in other districts, rocks of different kinds 

 are frequently brought together at the surface by means of faults. A 

 good example of this kind occurs on the shore at Cultra, near Belfast, 

 between high and low water-marks. At this place there are four or 

 five whin-dykes, all cutting through strata which are nearly level, in a 

 direction nearly at right angles to the line of shore (see Plate VI., Fig. 3). 

 The little quay at Cultra is built on one of them. Each dyke is the 

 boundary between two compartments of rock of different kinds : one of 



VOL. IV. Q 



