168 DISLOCATIONS ALONG THE MARGIN OF THE SOUTH WELSH BASIN. 



the abrupt escarpment of the chief mass, that the carboniferous limestone must once 

 have extended over a considerable portion of the valley, and probably far to the west- 

 ward of the castle. It is also evident from the opposite inclination of the strata on 

 each side of the gap at Cwrt-a-barddh and from the beds on which the castle stands 

 dipping away from the main escarpment, that the whole of the district has been vio- 

 lently broken up. We have therefore data for inferring, that the part of the valley 

 situated between the outlier and the boundary of the coal-field was once the scene of 

 a great disturbance, and that a body of water similar to that we have supposed to be 

 in existence in the case of Pen Cerrig Calch (p. 162.) has subsequently removed the 

 intervening masses of strata, leaving the Cerrig Cennen a monument of its devastating 

 action. 



It is not my intention to describe the other dislocations in the carboniferous limestone 

 on the south-western edge of the South Welsh coal basin, as they will form a portion 

 of Mr. Conybeare's memoir. It is sufficient to say that they all exhibit, though some- 

 times in a minor degree, nearly the same phenomena as have been here delineated. 

 Some of the general inferences which may be deduced from these facts will be noticed 

 in a subsequent chapter, after the reader has been made acquainted with the disruptions 

 of the older rocks. 



Repeating, however, an observation deduced from similar phenomena in the Clee 

 Hills, I will here merely observe, that the method by which the strata surrounding and 

 supporting this coal-field have been fashioned into the broken margin of a basin, is 

 clearly indicated by numerous and powerful transverse dislocations 1 . 



1 See p. 119. 



