42S Stralification of Glamorganshire. 



A grey variety streaked with red and white is worked at the 

 Mumbles by Mr. Wullis of Swansea, sawn into slabs and po- 

 lished. Near Pvle a reddish-grey variety occurs with green and 

 yellow veins : it is very hard, and contains no fossils. We may 

 observe it near Coity. Mytili, chamae, pelices, pectenites, gry- 

 phites, &.C. are found in some parts of the mountain lime. I have 

 hsematitic iron ore from Lanharan. The mountain lime rises 

 on the north side of the county near the Ddinas rock, Breck- 

 nockshire. Here I observed the laminated sulphate of haiyte, 

 coiitaining small crystals of sulphuret of iron partiallv converted 

 into green vitriol. Here two valuable veins of fire clay may be 

 seen. 



Red Ground. 



Beds of marl, red, blue and white, sometimes with narrow 

 beds of siliceous freestone, occur at Sully, Lavernock, Cogali, 

 Porthkcrry, where they pass into blue lias limestone. At Pcn- 

 naith Point, a bold headland, the stratification exactly resem- 

 bles Aust Cliff, Glocestershire, red rock marl with beds of com- 

 mon and striated gypsum. Barry Island consists of red ground, 

 lias, and mountain limes irregularly disposed. The tract along 

 the coast near Cardiff lies low, consisting of vast beds of pebbles 

 and gravel protected by a sea wall. 



Blue Lias. 



An acute angle one mile N.N.W. of Bridgend is the most 

 northern direction where we can trace the lias in Glamorgan- 

 shire, there it joins the coal-basin at Penyva. It is seen every- 

 where at Laleston, Tithegston, Merthyrmawr, where there are 

 very extensive caverns through which part of the Ogmore river 

 passes. It forms the cliffs a little west of Dunraven Castle to 

 Marcross, Monknath, Boverton, St. Athan, Aberthaw, where it 

 appears in the form of banks of shingles, Porthkerry tlience to 

 Fonmor, Penmark, Wenvoe, Lancarvan, Lantrythid, Llancadle, 

 Flemingston, Saint Mary Church, Landough, Llanmaes, Llan- 

 twit. Saint Doiiats, Lisworney, Colwinston. 



At Wick Cliffs E. of Dunraven the lias is 200 feet thick, 

 dipping a little S. About a mile west of Dunraven, the cliffs 

 assume a different character. A calcareous breccia with nodules 

 of chert, jasper, &c. (similar to that described by Mr. Gilby, 

 Phil. Mag. vol. xliv. page 246) underlies the lias for about half 

 a mile. The mountain lime rises from under the Sutton stone 

 a little to the N.W. of the caves. 



At Tresilian E. of St.Donats there is also a very extensive cave. 

 Numbers of fossil gryphites occur in thin seams of clay between 

 the lias beds, fossil wood in several states, silicified, or burning 

 with tlic smell of Camiel coal, of which it has the fracture. A 



coralline 



