624 EDWATtD HULL ON THE CLASSIFICATION 



"Grey and dark shales, with bands of flag- 

 Stage C. stone, clay-iroastone, and cemcnt- 



Yoredale Series. stones. Fossils abundant, Goniatites, . 



Posidonomya Becheri, &c 600 



Stage B Carboniferous Limestone. 



In the above series we have, in stage E, clearly the representa- 

 tives of the Gannister Beds with their characteristically marine 

 fauna, in addition to the Millstone Grit. It is somewhat doubtful 

 where the line between these two divisions should be drawn ; but 

 this is of little moment so long as we can be certain that they are 

 both there. The representatives of the [Middle] Coal-measures 

 (stage F) have been entirely removed by denudation. 



2. The Tyrone Coal-field. — This is the most important coal-field 

 in Ireland, as in it the Coal-measures (stage F) are developed to an 

 extent nowhere else equalled, and contain numerous beds of bitumi- 

 nous coal (see Section, fig. 2, p. 618). The Lower, or Gannister beds 

 are very largely developed, while on the other hand the Millstone 

 Grit and Yoredale beds are comparatively unimportant as regards 

 their vertical thickness. 



An admirable Eeport on the structure of this coal-field was drawn 

 up in 1829 by Sir R. Griffith for the Royal Dublin Society ; and since 

 then the Geological Survey of the district has nearly been completed, 

 and a memoir thereon by Mr. Hardman will shortly be issued. 

 The coal-field itself forms a triangular area, bounded along the north 

 by a large upcast fault, bringing to the surface the Carboniferous 

 Limestone, along the east by the Triassic formation (below which 

 the Carboniferous beds extend), and along the south by the natural 

 outcrop of the strata. At Drumglas Colliery the lowest seam has 

 been worked, its position being near the base of the Lower Coal- 

 measures (stage E). A synopsis of the Carboniferous series by Mr. 

 E. T. Hardman is published in the Trans, of the British Association 

 for 1874, from which the following section is condensed *. 



Section of the Tyrone Coal-field near Dungannon (fig. 2). 



Feet. 

 Stage F. Coal-measures. — Sandstones, shales, and clays, with eight or 

 ten coal-seams. Fossils : fish, Anthracosia, Lingula squamosa, &c. 

 (Coal island), plants, ferns, &c about 930 



Stage E. Gannister Beds. — Sandstones, shales, &c, and two or three 

 workable coals (Crenagh and Drumglas). Fossils: fish-remains, 

 Orthoceras, Goniatites, Productus, and Lingular about 1000 



Stage D. — Millstone Grit. — Coarse grits below the Drumglas Coal ,, 200 



Stage C. Yoredale Beds. — Black shales with bands of limestone, sand- 

 stone, and clay-ironstone nodules 600 



Stage B. Carboniferous Limestone (Dungannon). 



* "On the Structure of the Tyrone Coal-field," Bep. B. A. Trans. Sect. p. 77 

 (1874). 



t Lingula squamosa occurs in shales over the " Crenagh Coal," which is high 

 up in the Lower Coal-measures (see Geological-Survey maps, 6-inch scale, No. 47, 

 co. Tyrone) ; also above the Yard and Belteboy seams in stage F. 



