Mr. F. Forster's Observations 07i the South Welsli Coal Basin. Ill 



Grey Metal Stotie is the name given to strata containing a still greater proportion of 

 Argillaceous matter than Grey Post, but which are gritty to the touch, and retain in some 

 degree the structure of Sandstone. 



Grey Metal is a decided Shale, a little harder and coarser than Blue Metal. From their 

 lamellar structure. Grey and Blue Metal are called by the Welsh Miners, " Cliff or Clift," 

 and " Plate" by the Northern Lead Miners; in Staffordshire, and the central Coal districts, 

 " Bind or Clunch." The term Blue Stone is applied to a variety more massive in structure. 

 Grey mil, or Thill, is a name given to the peculiar bed of massive indurated Clay, which 

 generally forms the " sill" or floor of a seam of Coal. 



Black Stone, the " Black batt," of Staffordshire, is a Bituminous Shale, which very ge- 

 nerally forms the immediate roof of a seam of Coal. 



The term Wliin, used in the above section, and so frequently occurring in the sections of 

 the Newcastle Coal-field, is applied to a hard, brown, massive Sandstone, which neither in 

 appearance nor structure bears any resemblance to Basalt. It usually occurs in thin irregular 

 beds, or compressed nodules, called " Whin Girdles," which, though of minor consequence 

 in sinking, often materially retard the process of boring. These nodules, I have been in- 

 formed by Mr. Winch, principally consist of Felspar, and are fiisible at a moderate heat. 



The colouring matter of the Red Shale, of which three beds occurred in this section, was 

 different from any thing of the kind that I have seen in the north. It appeared to have been 

 held in solution by water at some former period, and to have been forced, as if by strong 

 pressure, into the minutest fissures in the Shale, which was of a purplish carmine colour, 

 and the water drawn out of the pit had a very delicate pink tinge. I have seen a somewhat 

 similar bed of Shale in Staffordshire. 



GENERAL OBSERVATIONS. 

 Faults, or Dykes. An examination of the section would lead to the 

 inference that the Welsh Coal district is unusually free from the dislo- 

 cations, known here by the name of " Upcast, or Downcast Dykes," and 

 in that country, by the name of " Faults, or Bars ;" but the very small 

 number intersected is owing to the bearing of the Dykes, which, generally 

 speaking, run in a north and south, or dip and rise, direction, and nearly 

 parallel therefore, to the line of section. A section taken for the same 

 distance (15 miles) along the water-level line, or drift of the strata, 

 would exhibit a more than ordinary proportion of those dislocations. 

 About two miles to the eastward of the point where the northern end of 

 the line commences, a Dyke, of many fathoms downthrow to the east, 

 passes alike through the Coal Measures, Millstone Grit, and Limestone, 

 considerably extending the width of the mineral Basin. A similar Dyke 



