406 Rev. W. D. Conybeare on M. de Beaumont's Theory 



greater than that of the Pontefract sandstone and dolomitic 

 limestone, which are usually undisturbed ; a supposition which 

 would enable us to refer these disturbances to the aera we are 

 now considering. It seems probable, but by no means certain, 

 that the elevation of the transition chains in North Devon and 

 on the adjoining borders of Somerset, such as the Brendon 

 and Quantock Hills, may be of this sera. The carboniferous 

 limestone of Cannington park, on the north of the Quantocks, 

 appears to conform to the elevation of that chain, which may 

 incline us to adopt this age. 



Entering on the Bristol coal-field we find its southern border- 

 ing chain, the Mendips, composed of carboniferous lime with an 

 axisof old red sandstone highly elevated, the disturbances equal- 

 ly affecting the incumbent coal-measures, but leaving the dolo- 

 mitic conglomerate undisturbed and nearly horizontal, so that 

 the age is here distinctly marked. This line of elevation ranges 

 nearly E. and W. a little inclining to W.S.W. and E.N.E.: 

 it is prolonged by the Isle of Steepholm in the Bristol Channel. 

 The elevation bounding the coal-basin on the west is more 

 complicated, being associated with parallel undulations and 

 disturbed by faults. It is continuously prolonged in a direction 

 somewhat tortuous, but generally bearing from S. to N. into 

 the centre of Herefordshire ; and as it is obviously of the same 

 age with the Mendip elevation, which ranges E. and W. af- 

 fecting equally the coal-measures and all the older rocks, 

 but leaving the younger dolomitic conglomerate and new red 

 sandstone undisturbed, it seems to afford a convincing ex- 

 ample that disturbances of the same age do not uniformly 

 pursue parallel lines: thus, it reaches Shackwell hill, 7 miles 

 east of Hereford, where it inosculates with the anticlinal 

 line which forms the western border, as the above does the 

 eastern, of the Forest of Dean basin. This ranges southwards 

 from Westhide by Kenchurch, where it crosses the Manno 

 River, as it does the Uske, a little west of Ryland, throwing 

 up the transition limestone thence to Uske. A few miles south- 

 east of this place this line, which has hitherto ranged north 

 and south, trends towards the west, hence forming the southern 

 boundary of the South Welsh coal-basin. Thus it affords us 

 an example, not simply of lines of elevation of the same age, 

 but of the same individual line, which, after pursuing a course 

 in one direction for 50 miles, curves round, and adopts for 

 100 miles a course exactly at right angles to the former. 

 It ranges north of Caerleon by Llandaff to Cowbridge: 

 thence ranging by Kenfig, it crosses Swansea Bay to Gower, 

 where it throws up the old red sandstone central chain of the 

 peninsula of Gower, thence crossing to Tenby, where we have 



