COAL FORMATION. 



COAL FORMATION. 



three miles. Near Tortworth the range extending from Almonds- 

 bury is deflected suddenly to the south, and this may be considered 

 the north-eastern frontier of the basin ; it may also be traced through 

 Wick war to Sodbury. The south-eastern limit, from Sodbury to 

 ii -;tr Mells, the eastern extremity of the Mendips, is mostly concealed 

 by overlying deposits. Partial denudations occur at Lansdown, near 

 Wick Rock, where the limestone can be traced in the valleys dipping 

 towards the centre of the coal basin. From Lansdown to the Mendips 

 the continuity of the basin can be well ascertained, the coal-measures 

 being uncovered in some of the valleys in which the principal collieries 

 are situated. In other places shafts have been sunk through the 

 overlying horizontal deposits beneath which the coal is worked. The 

 greatest length of this area is 25 miles ; the width, from the collieries 

 near Bath to those of Bedminster near Bristol on the west, is about 

 1 1 milei!. In this district there is much local irregularity, and the 

 stratification of the coal-measures is so deranged that they have very 

 different and varying levels. In some parts the beds are denuded, 

 in others concealed by the more recent horizontal deposits ; and thus 

 the whole basin is divided into several detached coal-fields. 



The uncovered areas may be divided into the northern, the central, 

 the southern, the eastern, and the western coal-tracts. The northern 

 is the most extensive and elevated : its greatest length, from the vertex 

 ( the basin near Tortworth to the village of Brislington on the left 

 bank of the Avon near Bristol, is 12 miles; its greatest breadth from 

 east to west is nearly four miles. The collieries of Iron Acton, Sodbury, 

 and Kingswood are in this coal-tract. Along the northern limits of 

 the basin, from Sodbury to Cromehall and Titherington, the coal- 

 measures are exposed in immediate contact with the limestone ; on 

 t!ie western, southern, and great part of the eastern border of the 

 tract they are skirted by hills of red marl capped by lias. At 

 I'ueklechiirch shafts are sunk to the coal through both the latter 

 formations. 



The central tract, which begins on the south of Dundry Hill, is 

 divided into two parts by a narrow valley ; the northern portion, 

 about six miles in length, extends from Burnet on the north-east to 

 Knowl Hill, near Stauton Drew, on the south-west; near Pensford it 

 is about two miles in breadth. The southern division, extending from 

 Temple Cloud on the west to between High Littleton and Timsbury 

 on the east, is about three miles in length. To the south-east of this 

 central coal-tract the coal-measures are entirely concealed by super- 

 jacent deposits through a distance of six miles. Throughout this space 

 however many shafts are sunk some through the red marl of the 

 valleys, and some through the lias which occurs on higher ground, 

 are several of the latter description in the parishes of Timsbury 

 ami Poulton ; but the deepest is on Clan Down near Radstock, which 

 is sunk 200 fathoms before its horizontal adits are driven. Another 

 shaft, beginning in the oolite, is sunk on the edge of the same Dnwn 

 near Paultou ; Imt it is not so deep as the former, since here there is 

 a rise in the strata, and the coal-seams are in consequence much nearer 

 the surface. On the ascent of the hill above Chilcompton the coal- 

 measures are again exposed to the extent of about an acre. 



The southern coal-tract commences near the point where the road 

 between Bath and Shepton Mallet crosses the Nettlebridge stream, 

 and ends between Vobster and Mells ; its greatest length is six mile*, 

 nnd greatest breadth two miles and a half. The coal-measures of the 

 eistern coal-tract are laid open in the vale of the Buoyd at Wick and 

 l"],t.in. both in Gloucestershire ; they are likewise exposed at Newton 

 St. Leo, on the left bank of the Avon below Bath, dipping towards the 

 interior of the basin. Several seams are worked at Upton and Newton. 

 Th>! western coal-tract lies ut the south-east of Leigh Down, near 

 Bristol. Beds of red marl form the upper strata in the shafts of all 

 the coal-pits of thi* tract between Long Ashton and Bedminster. The 

 coal-field of Nailsea, lying more to the west, is a continuation of thistract. 



A great undulation in the strata of the coal-measures which form 

 the coal-basin of Somersetshire and the south of Oloucestershirea, Iters 

 the apparent position of the seams so much that it is very difficult to 

 ascertain the identity of each throughout the various collieries. The 

 local nami-s of the several seams also tend to confuse the geologist. 



The chain of hills which limits the western boundary of this coal 

 di.-trict present* remarkable anomalies between Clevedon and Port- 

 bury along its northern escarpment. A great fault ranging along the 

 edge effects a very considerable subsidence of the strata. In conse- 

 i|in noe of this "the coal-measures, depressed to the level of the old 

 :idstone, appear to occupy its place, and seem to dip beneath 

 the [Mountain limestone, on which in fact they repose." (' Oeol. 

 Trans.,' vol. iv.) 



The following are the principal subdivisions of the Coal-Measures in 

 i*in, beginning with the highest : The Upper Coal Shale ; the 

 "it Grit (sandstone); the LowerCoal Shale; and the Millstone Grit. 



In the. Bedmiuster colliery on the south-west of Bristol there are 



.-">ams of good bituminous coal : the deepest and uppermost are 



worked : tin? former is 4 feet 3 inches, the latter 2J feet to 3 feet 



thick ; the middle seam is only 1 foot. The interval between the two 



11 seams is 23 fathoms ; the lowest shaft sunk is 127 fathoms 



'! |.. These beds are obviously referrible to the lower coal shale. 



In tl "f I'iti-'it, situated a little to the north-east of 



'Hrlt.'e, all the strata are vertical : a perpendicular shaft is 

 there mink to tie ilijith of 80 fathoms in one bed of coal. 



The total number of mines worked in this district is probably less 

 than it was formerly, but the whole produce is certainly much greater, 

 owing to improved methods in working. The seams of coal are very 

 thin in comparison with those which are worked in the principal coal- 

 fields of England, and in most of those would be rejected as not 

 worth the working. 



3. The Forest of Dean Conl-fiasin occupies an irregular elliptical 

 area, circumscribed by the triangle formed by the Wye, the Severn, 

 and the road from Gloucester to Ross ; the largest diameter from 

 north-north-east to south-south-west is about ten miles, the shorter 

 about six miles. All the strata dip uniformly towards the centre of 

 the basin. The whole of this coal-tract, together with the high land 

 that surrounds it, constitutes a mountain group, the average height 

 of which above the level of the sea is about 900 feet. The aggregate 

 thickness of the whole strata of the coal-measures is, according to Mr. 

 Mushet, 500 fathoms ; he divides the different strata into seven series, 

 in which there are 27 beds of coal. 



On the north of the Forest of Dean basin, and at the distance of a 

 few miles, is the Newent coal-field, a very small tract surrounded and 

 concealed by overlying strata of the new red-sandstone. 



Scotch Coal-Fieldt. Several small Coal-Fields occur in Dumfries- 

 shire, forming narrow basins in the valleys of the great southern 

 transition chain of Scotland. In the valley of the Nith, in the parishes 

 of Sanquhar and Kirkconnel, there is one of these coal-basins, about 

 7 miles in length and 2J miles in breadth. Three seams of workable 

 coal have been discovered, averaging in thickness from 3 to 4 4 feet. 

 The range of the seams is in the direction of the Nith ; the measures 

 are disturbed by a dyke running north and south, by which the strata 

 are much depressed on the east side. In the parish of Cauobie, 

 adjoining Cumberland,' coal is worked in two pits : the principal seam 

 is 5 feet 10 inches thick. 



The principal coal-district of Scotland occupies the tract which 

 forms the great central lowland of Scotland, and lies between the 

 great transition chain on the south and the still loftier primitive 

 mountains of the Highlands on the north. " The whole of this wide 

 tract is occupied by the coal-measures, the carboniferous limestone, 

 and the old red-sandstone, associated in every possible manner with 

 vast accumulations of every variety of trap." (Conyb. and Phil.) 



To begin with the most eastern county in this tract in which coal 

 is found : In the parish of Dunbar, on the east coast of Haddington, 

 there are indications of coal, but no seams have yet been found of 

 sufficient thickness for working. In the parish of Ormiston, in the west 

 of the same county, coal is found in abundance ; there are three 

 workable seams of coal, varying from 28 to 43 inches in thickness, 

 and the coal is of good quality. 



Coal occurs in Fifeshirc, on the north side of the Forth. There are 

 mines in the parish of Dysart, where coals were first raised in Scotland 

 nearly 400 years ago. Coal is wrought in several places in Mid-Lothian. 

 In Lanark the coal-fields are numerous and extensive. The Wilson- 

 town coal-basin and the Climpy basin both occur in the parish of 

 Carnwath; the latter is on the west side of the first, the crop of the 

 one nearly approaching the other. There are several seams of coal 

 in these baiiins. The main coal, or lowest, is called the 4-feet coal ; 

 another seam is about 2 feel in thickness. The accompanying strata 

 are sandstone, varying in composition and hardness, bituminous shale, 

 slate-clay, and thin beds of ironstone alternate with the coal. Several 

 small faults, or hitches, as they are here called, traverse the field. On 

 the south-west part of the field the main coal is generally 14 feet 

 below the crow coal, which is the next superior bed ; on the north- 

 east the space between the same beds is only about 2 feet. These 

 basins form part of the great coal-basin of the Clyde, which extends 

 on both sides of that river, and the centre of which is near DalzieL 

 On the same side of the river, in the parish of Moukland, there are 

 many collieries, in which the thickest bed of coal is 9 feet, and it is 

 of good quality. On the left bank of the river coal is wrought in 

 several places. Several mines are worked in the parish of Rutherglen, 

 and others in the adjoining parish of Cambuslang. There are several 

 also in Hamilton, Stonehouse, nnd Douglass. Throughout this dis- 

 trict seven seams of coal are usually found within 415 feet of the 

 surface ; five of these seams are of sufficient thickness and good 

 quality to be wrought. The following *hows the situation and thick- 

 ness of the seams of coal in the pits in the parish of Cambuslang : 



fuel. In. 



!"[>]Mrr woil (earth and clay) . , . from 20 to 30 



Argillaceous white freestone . . * . . 20 



Shale, with vegetable impressions, from 30 feet to 40 feet 35 



1 st Seam, soft coal ....... 46 



Interval (hard freestone, Ac.) . . . . 26 6 



2nd Seam, soft coal 36 



Interval (shale) 63 6 



3rd Seam, shaft coal 50 



f shale, 20 feet . . . . ] 



Interval < hard ironstone, from 6 to 18 inches > . 65 2 



[ shale and freestone . . . I 



4th Seam, soft coal 60 



i ( shale 00 A 



Interval ', > 83 



( freestone J 



