100 Mr. F. Forster's Observations on the South Welsh Coal Basin. 



tion is expressively termed by the Welsh miners the " Farewell Rock," 

 from the position which it occupies beneath the whole of the beds of 

 Coal and Iron-stone contained in the mineral Basin. 



Immediately upon the Millstone Grit, repose a thick series of Shale 

 beds, alternating with thin bands of hard Sandstone. The first visible 

 seam of Coal occurring in the Shale is 2 inches thick ; it is very proba- 

 ble however, that another seam called the " Rhos Vach," generally 

 about 2^ feet thick, crops out here. A few fathoms above this seam 

 there occur from 14 to 16 beds of Iron-stone, 9 of which are visible at 

 the surface ; they are embedded in Shale, and occupy a perpendicular 

 depth of 13 or 14 fathoms. Continuing their range to the eastward, 

 these are the principal beds from which the supply of Ore for the Welsh 

 Iron works is procured. At Cillia, a few miles to the eastward of the 

 line of section, a fine natural section has been washed by the rapid 

 stream of the river Twrch. These beds of Iron-stone are of an average 

 quality, the specific gravity of three specimens which I have examined 

 were o"30, 3*25, and 3"28 respectively ; they were obtained from the 

 out-break of the beds, and making allowance for the partial decompo- 

 sition consequent on their exposure to the atmosphere, they may be 

 considered as capable of yielding on the average, about 26 per cent, of 

 Iron. In addition to these beds, several others of which no correct 

 account could be obtained, are interstratified with the different seams 

 of Stone Coal which follow next in succession. 



These Stone Coal seams are ten in number, or, if the bands of Shale 

 which commonly separate the 8th, 9th, and 10th seams, be considered 

 as dividing them into distinct beds, the total number will be 13. There 

 is no apparent cause for the undulation in their line of dip, an irregula- 

 rity which does not take place to any great extent along the level line 

 or drift of the strata. These seams vary considerably in point of hard- 

 ness, and in the quantity of sulphur which they contain ; in other 

 respects they present no great variation in quality, and possess all the 

 decided characteristics of Stone Coal. These are the seams, from 

 which, (being changed into Free-burning Coal) the principal supply for 

 the Iron works in the N. E. part of the Basin is obtained. In their 

 range to the westward, by way of Llanon, Pont-y-berem, Trimsarren 



