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 



* " On the Counaught Coal-fields," Eep. to Eoyal Dublin Society, 1818. 



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. 



|| ' Geology of Yorkshire,' part ii. p. 11 (1836). The name is there spelt 

 " 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 divisional line between stages D and E is rather uncertain. Possibly 

 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. 



