COAL MEASURES, 185 



Hiiddersfield, Barnsley, Sheffield, Chesterfield, and Staveley, to the 

 country between Derby and Nottingham.^ (See Fig. 28.) 

 The strata are thus divided : — 



Upper Series. — Red beds with coal-plants of Conisborough pottery, near 

 Rotherham, etc. 54 feet. 



Middle Series. — Sandstones, shales, and clays, with ironstones and coal- 

 seams (Cannel Coal, etc.), Anthracosia, Fish-remains, etc. 2000 

 to 3000 feet. 



Lower or Canister Series. — Flagstones and shales, with thin coal and Canister 

 floors. Marine fossils in places. 900 to 1600 feet. 



Mr. J. W. Davis has obtained many Fish-remains from the Cannel 

 Coal and other beds in the Coal-measures. In most instances they 

 are found on the surface of the coal, rarely in the shales above, 

 and never in the sandstone. Near Bradford the Fish-remains form 

 quite a Bone-bed above the Better-bed Coal in the Lower Coal- 

 measures.^ 



The seams of coal vary from two to nine feet in thickness. In 

 Derbyshire the principal coals are the "Top hard" and "Lower 

 hard " seams, producing the valuable splint-coal, also the " Upper 

 soft" and " Lower soft " coals ; and in Yorkshire the most remark- 

 able are the " Silkstone" and " Barnsley thick coals." The former 

 is identical with the " Arley Mine" of Lancashire, and has the 

 highest reputation as a house coal. Silkstone is a village west of 

 Barnsley. Clay Cross near Chesterfield, and Shireoaks near 

 Worksop, are well-known localities in this Coal-field. The 

 Adwalton stone coal is also an important bed. 



The Better-bed coal (from 6 in. to 2ft. 6in.), worked at Low 

 Moor, Bowling, and Farnley, near Bradford and Leeds, is a 

 ' bituminous ' coal, well adapted for smelting purposes on account 

 of its freedom from sulphur and other impurities. (See p. 177.) 



The Black-bed ironstone of Low Moor, etc., yields about 30 per 

 cent, of metallic iron, and occurs in layers and nodules in car- 

 bonaceous shale, altogether about ift. loin. thick. The Tankersley 

 or Mussel-bed ironstone in the Middle Coal-measures near Sheffield 

 is often full of specimens of Anthracosia. The Honeycroft iron- 

 stone is a local bed in the Derbyshire Coal-measures. 



Fireclay, which occurs beneath the Better-bed coal, is worked at 

 Wortley near Leeds. In composition it contains 56 per cent, of 

 silica, and 31 of alumina. The term Canister or Calliard is used 

 to designate a peculiarly hard and fine-grained siliceous sandstone, 

 which sometimes forms the floors of the seams of coal in the Lower 

 Coal-measures. It is often penetrated by the roots known as 

 Stigmaiia ficoides. Economically, it is used for road-metal, and 

 when ground down and mixed with fireclay, it makes excellent 

 fire-bricks, or forms a good fire-resisting lining for the inside of 

 furnaces. Near Bradford the Canister is ground to a fine sand, 

 and used in the casting of iron and brass. 



^ See Geology of Yorkshire Coal-field, by A. H. Green and others. 

 ^ Q.J. xxxii. 332, x.xxvi. 56 ; P. Geol. Assoc, vi. 359. 



