COMPARED WITH THOSE OF CAERMARTHEN BAY. 



375 



of the oldest sedimentary deposits. The "arkose" of central France, where beds of 

 the tertiary epoch (Eocene of Lyell), have the aspect of the oldest secondary or 

 transition rocks, is an admirable illustration of this point 1 . 



The three following diagrams represent the principal different positions in which 

 culm measures occur in Pembrokeshire. 



S. Caermarthen Bay, East Pembroke. N. 72. 



St. Bride's Bay, West Pembroke. 

 73. W.S.W. Nolton (W. Pembroke). E.N.E. S. Near Brawdy. N. 74. 



(&, c % d wanting.) (c, d 8f e wanting.) 



a. Culm Measures. b. Millstone Grit. c. Carboniferous Limestone. d. Old Red Sandstone. 



e. Silurian Rocks. /. Cambrian Rocks. 



I have already stated enough to show, that sections made in different parts of the 

 country will materially disagree in the order and succession of the culm bearing strata. 

 Let any one desirous of studying this fact only pace the strand at low water from Druson 

 Haven as a centre, and proceed southwards to Broad Haven and Little Haven, or north- 

 wards to Nolton and Newgale sands ; and he will see a series of breaks, curvatures, 

 thinnings out, and contortions, which cannot be exceeded even in imagination, and 

 ought to be a warning to those who would speculate heedlessly in culm works, amid 

 these convulsed strata. 



Yet even in this neighbourhood there are spots, where the seams multiply and continue for short 

 distances, and have been worked to some profit. One of the most remarkable of these pro- 

 ductive tracts lies to the north of Nolton, where nine or ten beds (veins as they are here called) of 

 coal have been wrought.. The uppermost is in the coast cliff, whence it bends to the north-east 

 and south-east, and all the underlying seams, curling round conformably, rise in succession (about 

 2 ft. 4 in. in a fathom) and occupy the interior of the country between Simpson and Bathesland. 

 (These are marked on the Map.) The ends of several of these coal beds can be traced on the 

 sides of the Nolton Brook, whilst the underlying grits and flagstones emerge to the east of Nolton, 

 where they are in contact, as above stated, with Silurian shale. (See wood-cut above.) Through 

 the complaisance of Mr. Higgon, the chief proprietor of the coal mines of Nolton, who is beginning 

 to work some of them in a spirited manner, I obtained the following list of strata as proved by 

 various works. 



i See the excellent work of M. Bertrand de Doue on the Puy en Velay; also Lyell and Murchison, "sur 

 le Cantal." Annales des Sciences Naturelles, tome 18, Octobre, 1829. 



3 a 2 



