108 Mr. F. Fobster's Observations on the South Welsh Coal Basin. 



Penclawdd. The angle of inclination gradually increases in advancing 

 to the southward until the lowest beds become elevated to about 45, or 

 6 feet per fathom, and upwards ; the whole of the seams have neverthe- 

 less been worked to a certain extent principally for the household con- 

 sumption of the inhabitants ; they are all bituminous, but the greater 

 proportion of them very soft and tender, and of very inferior lustre ; 

 owing, however, to their general freedom from Sulphur they are very 

 well adapted for many manufacturing purposes. 



The seams in this division are twelve in number, and their total thick- 

 ness 52 feet ; the number of searfis cropping out to the south of the 

 centre will, therefore, be twenty-three, and their aggregate thickness 

 104< feet ; thus exceeding, by 19 feet, the seams known to occur on the 

 north side of this part of the Basin, although the north-crop seams are 

 twenty seven in number. This difference may, in some measure, be ac- 

 counted for by the greater inclination of the south-crop seams, tending 

 to increase their perpendicular thickness, which, as regards those furthest 

 south, has probably been given instead of the real thickness. The great 

 thickness of tlie interposing beds of Shale and Sandstone near the 

 southern, as compared with the northern edge of the Basin (which will 

 be at once perceived on comparing the two ends of the section) renders 

 it probable that the whole formation, Coal seams included, thins out in ap- 

 proaching the north. 



The south crop of the underlying beds of Ironstone have not, to my 

 knowledge, been observed in the district crossed by the section, but 

 there can be no doubt of their existence, as they have been worked on 

 the opposite, or western side of Carmarthen Bay ; and at a place called 

 Cefn Cribbwr, near Pile, on the east side of Swansea Bay, they may be 

 seen interposing between the lower Coal seams and the Millstone Grit. 



I am not aware of the thickness of the Millstone Grit and Limestone 

 at their soutli crop ; the Limestone is very compact, the lower beds 

 crystalline, and abounding in Encrinites ; on the east side of the pro- 

 montory of Gower it is variegated, and has been quarried for Grey 

 Marble. It has been already observed that the Limestone, by a change 

 in its dip to the southward, extends into the Bristol Channel, where it 

 probably forms another Trough or Basin containing Coal Measures. 



