THE CARBONIFEROUS SYSTEM. 701 



2. Fields detached in north Yorkshire, of very limited extent. 



3. Field of south Yorkshire, Nottingham, and Derbyshire, extending from the north-east 

 of Leeds to the north of Derby, a length of sixty-five miles, by a width, at the greatest, 

 of twenty-three. 



4. Fields of north Staffordshire two detached one at Newcastle under Lyme, the 

 most important, and the other at Cheadle, of small consequence. 



5. Field of south Lancashire, or Manchester, extending from the north-west of Derby 

 shire nearly due north to Rochdale, and from thence westward to Preston, having a 

 general crescent-shape. 



6. Field of north Lancashire, between Lancaster and Ingleton. 



7. Field of Whitehaven, on the west coast of Cumberland. 



CENTRAL COAL DISTRICT. 



8. Field of Ashby de la Zouch, occupying an irregular area, the longer diameter of which 

 is about ten miles, and the shorter eight. 



9. Field of Warwickshire, reaching from the neighbourhood of Coventry to that of 

 Tamworth, sixteen miles in length, by an average breadth of three. 



10. Field of South Staffordshire, or Dudley, extending from Brereton near Rugeley to 

 near Stourbridge, about twenty miles, having its greatest breadth, from Walsall to 

 Wolverhampton, about seven miles. 



WESTERN COAL DISTRICT. 



11. Field of Isle of Anglesea, a valley traversing the whole island, at various points of 

 which coal has been worked. 



12. Field of Flintshire, extending from the western cape of the estuary of the Dee to 

 near Oswestry in Shropshire, a distance of thirty miles, but far from being worked 

 throughout. 



13. Field of Coal-brook Dale, on the Severn, six miles long, by two broad. 



14. Field of the Plain of Shrewsbury, east of the Wrekin chain, consisting of small, 

 detached patches of coal-strata, of very limited extent. 



GREAT SOUTH-WESTERN COAL DISTRICT. 



15. Field of South "Wales, extending from Pontypool on the east, to St. Bride's bay in 

 Pembrokeshire, on the west, upwards of a hundred miles in length, with a breadth 

 varying from four to twenty. 



16. Field of Somerset and south Gloucester, an irregular area, bounded by Bath on 

 the east, and Bristol on the west, about eleven miles, the Mendip Hills on the south, and 

 Coleford on the north, about twenty-five miles. 



17. Field of the Forest of Dean, an irregular elliptical area, bounded by the Wye, the 

 Severn, and the road from Gloucester to Ross, the longer diameter ten miles, and the 

 shorter six. 



The more important of these fields are those numbered 1. 3. 5. 10. 15, and 16, yielding 

 coal, of which there are three principal varieties. 1. Stone-coal, containing little or no 

 bitumen, but much earthy matter, producing a large quantity of ashes, the prevailing kind 

 furnished by the Staffordshire pits. 2. Caking-coal, containing about forty per cent, of 

 bitumen, the kind found in Durham and Northumberland. 3. Cannel coal, containing 

 about twenty per cent, of bitumen, occurring in Lancashire. All these varieties are some 

 times obtained from the same pit. The quantity raised in the United Kingdom in the year 

 1855 amounted, in round numbers, to 64,000,000 tons, of which somewhat less than one- 

 fourth was obtained from the Durham and Northumberland field. The next largest amount 

 was little more than half this quantity, produced in Lancashire, and was nearly equalled 



