185 



Blue sandstone. 



Brown sandstone. 



Argillaceous shale, with small pins of ironstone. 



Strong grey sandstone. 



Dark sandstone and argillaceous shale. 



Dark grey sandstone. 



Light brown sandstone. 



Conglomerate or plum pudding stone. 



This section I have obtained from that of the Ebbwvale measures. One 

 peculiarity of this district is, the immense quantity of sulphuret of iron contained 

 in it, the decomposition of which gives rise to numerous chalybeate springs. One 

 about two miles from my house, contains iron and sulphurretted hydrogen in 

 such quantities as to taint the air immediately aroimd it. 



At first view of the Coal district, one is struck with the parallel ridges of 

 sandstone running south, and forming the equivalent of the Pennant grit. They 

 are a marked feature in the whole of the South Wales Coal field. Commencing 

 at LlaneUy, Caermarthenshire, they run east to Swansea, where they attain the 

 great thickness of 2125 feet, and from thence may be easUy traced to Pontypool, 

 running in parallel ridges due north and south. The denudations which have 

 acted on the softer shales below, have been resisted by this hard rock. According 

 to Sir H. De la Beche, they are formed in the following manner : — he considers 

 the principal mass of sand to have been forced along the bottom by the pressure 

 and movement of superincumbent water, but little having been thrown down in 

 plane horizontal surfaces from mechanical suspension in the water. It is a kind of 

 deposit which, if the sand be readily supplied, may be effected in very shallow 

 water ; and hence, by continued subsidence, a very great thickness might be 

 eventually obtained. There are but few coal seams in this rock, at least with us, 

 but at the Town HiU, at Swansea, there are, by Mr. Logan's section, at least 

 twelve seams of considerable thickness, accompsinied by their underclay and a 

 considerable amount of shale. At Ebbwvale we find it of a thickness of 330 

 yards, consisting of 



Sandstone, with thin seams of coal and underclay. 



Troed y rhiw coal, 2 ft. 4 in. 



Underclay. 



Sandstone. 



Coal, I ft. 6 in. 



Carbonaceous shale. 



Sandstone. 



Coal, I ft. 2 in. 



Underclay. 



Shale, continued seams of coal, and underclay. 



Argillaceous shale continued, pins of ore. 



Oldman's coal, 2 ft. 4 in. 



Underclay. 



