BEVAN — ON THE SOUTH WALES COAL-FIELD. 



95 



I will not weary my readers with a full list of all tlie measures 

 here, with their accompanying shales, sandstones, and iron-ores,* 

 suffice it to say that there is an aggregate thickness of forty-six feet 

 of coal between the Pennant rocks and the mihstone-gTit. I mil first 

 run over the names of the more important seams, for the purpose 

 of identifying them with those in other valleys. In no district in the 

 world probably is there such a hopeless confusion of nomenclature as 

 regards the coal-measures ; one valley sometimes differing altogether 

 from the next in the names of what are precisely the same seams. 

 It may be easily imagined that difficulties may thus be thrown not 

 merely in the way of geological science, but also in the identification 

 of measures in different parts of the basin. 



The principal seams at Pontypool are as follows : — 



Ft. in. 



Mynyddswlyn Vein 3 0 



Troed-y-rhiw 2 0 



Coal 3 0 



New Vein 4 0 



Red Vein 2 6 



Rock Vein 7 6 



Yard 2 6 



Meadow Vein 4 6 



Stone Vein 4 0 



The Troed-y-rhiw coal is the highest in the lower measures, and 

 occurs also at the base of the Pennant-rock ; there is, nevertheless, 

 a considerable amount of sandstone generally found between it and 

 the next vein. Its general thickness is not great, seldom above two 

 and a half feet, but in aU the valleys it is much worked under 

 different names, owing to its accessibility and its constancy of 

 position. Thus the Troed-y-rhiw coal of Pontypool is called at 

 Abertillery the Cwmtillery or Tilestone-coal ; in the Cwm Came, 

 the Pontgwaithairam ; in the Ebbwvale valley, ISToed-y-rhiw ; and in 

 the Rhynmey valley, the Brithdir. 



Above this coal he what in Glamorganshire would be called the 

 middle measures, but which in Monmouthshire is simply unproduc- 

 tive sandstone, known as Pennant rock ; at Pontypool it is about 

 eight hundred feet thick, and immediately above it Hes the only 



* They will be found in the Memoirs of the Geological Survey, vol. i., page 174. 



