136 rilOCEEDINGS OF SOCIETIES. 



views were correct in the gross, they were liable to objection in detail, 

 inasmuch as many localities, represented by the blue colour as limestone, 

 rarely contained any calcareous rocks sufficiently pure to produce caustic 

 lime when burned, which is the agricultural test of limestone ; and, as 

 several landed proprietors complained of my want of accuracy in this 

 respect, I determined to subdivide the System, so as to distinguish the 

 shales and sandstones where each occur ; and I have in consequence in- 

 troduced the Yellow Sandstone and Carboniferous Slate, forming the 

 lowest members of the series, and the Calp, which is interposed between 

 the Lower and Upper Limestone. 



In the paper just alluded to Mr. Kelly gives it as his opinion, that 

 the Carboniferous Limestone of Ireland consists of one uninterrupted 

 accumulation of limestone beds, interposed between the Carboniferous 

 Slate at the base and the Millstone Grit at the top, and that my subdi- 

 visions of the Limestone series into three, viz., the Upper and Lower 

 Limestone, with an intermediate series, consisting of dark-gray shale, 

 impure limestone, and occasionally sandstone, called Calp, is erroneous; and 

 that no such middle term exists in Ireland or elsewhere. This is a bold 

 assertion ; but by reference to plans and sections, carefully made, I have 

 no doubt of being able to prove that Mr. Kelly is in error, and that my 

 views, as shown in the last edition of my large " Geological Map of Ire- 

 land," are correct. 



This triple division of the Carboniferous Limestone was first published 

 by me at the meeting of the British Association for the Advancement of 

 Science, held at Liverpool, in the year 1837; and an abstract of my 

 paper on the subject is contained in the proceedings of the Geological 

 Section C, page 88, of that year, to which I beg to refer. I have for- 

 tunately preserved the section exhibited at the meeting, which shows 

 the grounds on which my subdivisions of the Carboniferous System, as 

 regards Ireland, were based. 



This section exhibits the geological structure of the Carboniferous 

 System for a distance of fifty miles, in an east and west direction, com- 

 mencing in the Silurian strata near Butler's Bridge, in the county of 

 Cavan, and extending westward by Belturbet to Slieve Rushen moun- 

 tain, crossing Cuilcagh mountain, the valley of the Shannon, Lackagh, 

 and Benbo mountains, and terminating on the sea-shore at the western 

 base of Benbulben mountain. 



In the neighbourhood of Butler's Bridge the Silurian strata are 

 covered unconformably by strata of yellow sandstone, which are succeeded 

 by a band of Carboniferous Slate, and afterwards by the Lower Limestone, 

 which near Drummany Lough, two miles west of Belturbet, is succeeded 

 by alternating beds of shale and impure limestone of the Calp series, 

 together with gray and occasionally reddish sandstone. These strata 

 extend westward from Drummany Lough, by Ballyconnell, to the base of 

 Slieve Rushen, for a distance of about four miles, where they are succeeded 

 by the gray splintery limestone (Upper Limestone) of Slieve Rushen, 

 which in this locality is upwards of 400 feet in thickness. This lime- 

 stone is capped on the summit of the mountain by sandstone belonging 



