BEVAN — ON THE SOUTH WALES COAL-FIELD. 
95 
I will not weary my readers with a full list of all the measures 
here, witli 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 Peunant rocks and the miUstonc-grit. I will 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 diflferiug 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 diSerent 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 all the vaUeys 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 Pontgwaithaii'arn ; in the Ebbwvale valley, Noed-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 lies the only 
* They will be found in the Memoirs of the Geological Survey, vol. i., page 174. 
