Mr. F.Forstlr's Observations on the South Welsh Coal Basin. lOS 



siderable quantities have been already shipped to London under the 

 denomination of " Llangennech Coal." Up to the point shewn on the 

 section by the letter C, the line proceeds in the direction of "full dip" ; 

 the general inclination of the strata from the northward to the Freestone 

 quarry, about 150 yards south of the Penprys pits, being about 12i°, or 

 about 16 inches per fathom ; at this quarry, and southward until they 

 reach the centre, the dip does not exceed 8°, or about 10 inches per 

 fathom, and near to the centre it is probably even less. Owing to a 

 change in the direction of the dip of 80° to the westward (viz. from S, 20 

 W. to N. 60° W.), the line proceeds along the water-level course of the 

 strata from c, to the centre at d. 



The direction of the centre, or trough, technically called the 

 " Saddle," at the point where it is crossed by the section, is about N. 

 &%° W. and nearly parallel, therefore, to the dip of the strata on its nor- 

 thern side ; whereas on its south side the line of dip and rise immedi- 

 ately changes to about S. 30° W., thus forming a right angle with the 

 dip and rise line on the north side. This change can, I think, only 

 be accounted for by supposing that the strata, being broken in the 

 centre, have slipped downwards on its south side. That a break in the 

 strata has actually taken place, will be made fully apparent by the 

 following section taken at Pencbed, about half a mile to the eastward of 

 the point where the line of section crosses the centre. 

 SOUTH. DIAGRAM, No. 1. 



NORTH. 



The strata (c) on the north side of the centre (6) dip to the S.W. at the rate of about 

 12 inches per fathom, and the strata (a) on the south side rise to the south at the rate of 

 about 25 inches per fathom. The rock in the centre for several yards is perfectly vertical, 

 and seems to be composed of the broken edges of the inclined strata on each side, which are 

 composed of hard Sandstone. 



That this break in the strata and change of their dip and rise line is 

 only of partial extent, at least to the westward, will be shewn by the 



at a few hundred yards to the west of the line of section, and named, in honour of the Patron 

 saint, the St. David Pit. 



