140 PROCEEDINGS OF SOCIETIES. 



tigated in the field the grounds on which his theory of gigantic faults is 

 based ? 



I will now refer to a paper read by me at the meeting of the British 

 Association held at Cork in the year 1843, in which I described in detail 

 the strata which occur on the north shore of Lower Lough Erne, extend- 

 ing in an eastern direction, an abstract of which Will be found in the 

 " Proceedings" of that year, Section C, page 42, from which I may 

 quote the following : — 



" Mr. Griffith next described the district situated to the north-east of 

 Lough Erne, which contains a great variety of strata, belonging to the 

 Carboniferous, the Silurian, and the Mica Schist Systems. The suc- 

 cession of the strata as they occur in this interesting district was exhi- 

 bited in two sections, one of which extended from the Mica Schist 

 District of the county of Donegal, north of Pettigo, across the limestone 

 and sandstone valley of Pettigo, Kesh, and Ederney ; it afterwards tra- 

 verses the brownish-red conglomerate and sandstone district of Lisnarick 

 and Irvinestown, and, in continuation, the dark-gray slate district of 

 Lisbellaw, which contains Silurian fossils ; from whence it is continued 

 across the limestone valley of Brookborough, thence over the Slievebeagh 

 mountains, and terminates in the graywacke slate district of the county 

 ofMonaghan, — thus exhibiting the structure of the country for a length 

 of forty- two miles. 



" Commencing at the northern extremity of this, the most southerly of 

 these sections, — that near Pettigo, — we find the mica schist covered in 

 an unconformable position by a bed of red conglomerate, about fifty feet 

 in thickness, which is succeeded by beds of yellow sandstone, alternating 

 with dark-gray shale, and occasional beds of dolomitic limestone. The 

 shale contains the casts of plants, and also in abundance JModiolaMacadami. 

 These strata are about 150 feet in thickness. Above we have alterna- 

 nations of dark gray shale with occasional beds of gray sandstone, and a 

 few beds of calcareous clay ironstone, sixty feet thick. This mass of 

 shale and sandstone is succeeded by a series of beds of blue limestone, 

 occasionally alternating with dark gray shale and yellowish-gray sand- 

 stone, 500 feet in thickness. It is remarkable that a thin bed of coal, 

 half an inch thick, is included between two of the limestone beds at the 

 base of this division. The limestone is frequently dolomitic, and, as is 

 usual in such cases, fossils are of rare occurrence. Above, we have a 

 succession of beds, consisting of alternations of limestone and dolomite, 

 about 100 feet in thickness, followed by alternations of dark gray, im- 

 pure limestone, and black and gray shale, 300 feet thick, on the top of 

 which we have beds of gray siliceous limestone, about sixty feet in 

 thickness. These calcareous strata are succeeded by a great accumulation 

 of beds, consisting of gray sandstone and shale ; in some places the sand- 

 stone, and in others the shale, predominates, the whole being interspersed 

 with occasional beds of impure limestone, amounting altogether to a 

 thickness of about 700 feet. The shale contains in abundance Modiola 

 Macadami, and the usual fossils belonging to the shale beds. 



