822 



COAL 



465 



fig. 465 ; n, sandstones ; b, shales ; c, culm or anthracite ; so that the culm itself scorns 

 the result of irregular accumulations of vegetable matter intermingled with mud and 



sand. As so frequently 

 happens with carbona- 

 ceous deposits of this 

 kind, nodules of argilla- 

 ceous iron-stono are often 

 found in the same loca- 

 lities with the shales and 

 anthracite, reminding us 

 of the intermixture of 

 iron ores and vegetable 

 matters in the bogs and 



f, a^^ a. ' j ^ ^e >vw A "V * & " " a morasses of tho present 



day.' DC la Bcche. 



SOMERSETSHIRE AXD GLOUCESTERSHIRE. The Dean Forest coal-field, and tho coal- 

 measures extending further south forming the Bristol coal-field, are included in this 

 division. Tho workable seams of coal in tho Forest are the following : 



ft. 



Dog Delf (having a thickness of) 1 



Smith Coal 



Little Delf 



Park End High Delf 



Stakey Delf 



Little Coal 



Hocky Delf 



Upper Churchway Delf 



Lower Churchway Delf 



Braizley Delf 



Nag's Head, or Weaver's 



Whittington Delf 

 Coleford High Delf 

 Upper Trenchard 

 Lower Trenchard 



in. 



2 



6 



8 



7 



6 



1 



9 



There is a small coal-field north of the Forest of Dean, which is a long narrow 

 strip, containing two and a half square miles or 1,600 acres. Maclauchlan, Geological 

 Transactions, vol. v. 



About nine miles and a half to the south of Dean Forest a considerable mass of 

 coal-measures has been preserved from destruction, by the denuding causes whicli 

 have carried off the connecting portion between it and Dean Forest, leaving at least 

 two outlying patches on the north of Chepstow. 



The Bristol coal-field occupies about fifty square miles, or 32,000 acres. Tho 

 seams of coal are very thin in comparison with those which are worked in other 

 districts. Buckland and Coneybeare (' Geological Transactions,' vol. i.) have well 

 described this coal-field. 



The total thickness of the whole series of strata in this Bristol coal -field has been 

 shown by De la Beche to be as follows : 



Upper shales and limestones 

 Middle sandstone 

 Lower shales . 

 Farewell Eock . 



1,800 feet, with 10 beds of coal. 

 1,725 feet, with 6 beds of coal. 

 1,565 feet, with 36 beds of coal. 

 1,200 feet. 



Total . . . 6,290 feet. 



SOTITH WALES COAL-FIELD. Tho total thickness of the coal-strata in this im- 

 portant district is very great. Logan and De la Beche have accumulated evidence 

 which appears to justify the admission of 11,000, or even 12,000 feet thickness from 

 the carboniferous limestone to the highest part of tho coal scries about Llanelly ; in 

 other parts of tho field the series is found to bo on proportions only less gigantic. Tho 

 most general view which can bo afforded seems thus, giving tho true coul-nieasuro 

 about 8,000 feet: 



Feet 



Llanelly series, with several beds of coal 1,000 



Penllergare series of shales, sandstones, and beds of coal, 110 beds ; 



26 beds of coal 3,000 



Central series (Townhill sandstones of Swansea, Pennant grit of the 

 Bristol field); 62 beds, and 16 beds of coal . . . . . 3,246 



