Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/727

Rh OP THE CARBONIFEROUS SERIES. 023 B. The Northern Coal-district. This includes the Leitrim and the Tyrone coal-fields, of which a short description will suffice, as several accounts with very full details are already in existence, my only object being to show how the successive stages which can be recognized in the south are also here fully represented. 1. The Leitrim Coal-fields. — These have been described by Sir R. Griffith*, Sir E. Kanet, the late Mr. Du NoyerJ, and Mr. Readwin. They are now being surveyed by Mr. Cruise, of the Geological Sur- vey ; and some of the maps are already published §. They occur in the form of several detached tablelands on both sides of Lough Allen, from 1000 to 1377 feet above the sea. The Yoredale shales are, as is well known, rich in beds of ironstone, which were formerly smelted at the Arigna Ironworks, built on the western shore of the lough. The beds of coal, three in number, occur partly in the Millstone Grit, which rises in terraced escarpments above the slopes, and in Cuilcagh reaches an elevation of 2188 feet, giving rise to scenery resembling that of the Yorkshire and Derbyshire uplands. The succession of the beds from this mountain to Enniskillen is given by Phillips in his 'Geology of Yorkshire '||. It requires some modification, but is in the main correct. The general series of Lough-Allen beds is as follows, in descending orderT : — Section at Kilronan, Co. Leitrim. [1. Flaggy grits and shales 180 I 2. Dark shales with thin flagstones, and Stage E. numerous marine fossils — Goniatites Gawnister Beds. crenistria, Orthoceras Steinhaueri, Po- sidonomya Becker i 170 O Topcoal 2 6 ( Hard massive grit 40 to 60 Dark-blue shales with ironstones 40 Second coed 1 6 Stage D. J Hard grit 5 Millstone Grit**, ] Shales with a thin coal and marine shellstt 10 Massive hard grit, fine-grained, with nume- rous stems of Lefidodendron, Sigil- laria, &c 80 t ' Industrial Resources of Ireland,' 2nd edit. "On the Bituminous Coal of the Arigna District," Geol. Mag. March 1863. § Mr. R. J. Cruise, who has surveyed this district, has also made analyses of the coal, which approaches " steam-coal " in quality. " Kulkeagh." % ' Coal-fields of Great Britain,' 3rd edit. p. 308. In my description of this distinct I have given a section founded on that by the late Mr. Du Noyer. the beds above the lowest Millstone Grit may probably be placed in stage E. ft The following species, determined by Mr. Baily : — Aviculopecten, Ehyn- chonella pleurodon, Posidonomya Becheri, P. B., var. membranacea, Goniatites crenistria, Lunulocardium Footi (Baily). Also a species of Palceoniscus.
 * " On the Counaught Coal-fields," Eep. to Eoyal Dublin Society, 1818.
 * ' Geology of Yorkshire,' part ii. p. 11 (1836). The name is there spelt
 * The divisional line between stages D and E is rather uncertain. Possibly