COAL OR CULM MEASURES IN CAERMARTHEN BAY. 



373 



The culm in this pit is much broken, and the surfaces of the fissures are frequently coated with 

 mineral charcoal, but in other parts it presents its ordinary pure, clean, and polished fracture. It 

 is much used by maltsters. Plants common in other coal-fields occur not only in the shale but 

 may be detected in the culm itself. 



Even in this comparatively regular portion of the field, faults are very numerous, some affecting 

 the strata to the extent of fifteen fathoms, and they are all upcasts to the north. (For the general 

 relations of these coal beds to the associated strata see PI. 35. f. 4.) 



In the Fraisthorpe Colliery, on the west or opposite bank of the river, four beds only of coal 

 have been found, though the shafts are deeper than at Landshipping. It is, therefore, obviously 

 impracticable to ascertain correctly the general succession of productive coal beds by sections 

 made in any particular district. 



At Amroth, for example, near the eastern extremity of the field, there is but one bed of workable 

 coal, varying from 6 inches to 1 foot in thickness, while on following the coast cliffs westward to 

 Tenby or the centre of the basin, the beds of coal multiply so rapidly, that at Wiseman's Bridge 

 there are seven, varying from 4 inches to 22 in thickness. At Saunder's-foot the three principal 



. the following order : 















Fath. 



yds 



. ft. 



in. 







. .. 10 



0 



0 



0 





3 tn 4 ft. 









0 



0 



0 





1 to I 



1 ft. 









0 



0 



0 







5 ft. 



The total depth of the shaft is 49 fathoms, and the dip nearly 45° southerly. This is one of the 

 spots where, the strata not being violently contorted, the coal is largely and profitably extracted ; 

 but in the coast cliffs between Wiseman's Bridge and Amroth, the curvatures and breaks are so 

 numerous, that although the outcrop is sometimes clearly exposed, the bed is persistent only a few 

 yards, being lost amid convulsions of the strata. 



Although I have spoken of the eastern culm tract as the most regular, the expres- 

 sion must be understood to apply to the general structure of the district, including the 

 millstone grit and carboniferous limestone ; the beds of culm being for the most part 

 as much contorted as in the western tract, and to an extent, which those who have 

 studied only the coal measures of the North of England, or of the central counties, 

 cannot depicture to themselves. These phenomena are fully exhibited between Amroth 

 on the east and Tenby on the west. At the latter place, indeed, a dislocation by which 

 the lower part of the carbonaceous beds is brought into abrupt contact with the moun- 

 tain limestone, is beautifully displayed 1 . 



Western Culm Tract. (PL 35. f. 7.) 



The carboniferous strata are continuous from Caermarthen Bay and the east of Pem- 

 broke, by Freystrop and other places, to St. Bride's Bay on the west coast. 



1 This fault is noticed by Mr. De la Beche. (Geol. Trans. N.S. vol. ii. p. 15.) 



3 A 



