76 © REPORT—1848. 
principal valleys, down which the mineral produce is conveyed by canal or railway to 
the several ports of Cardiff, Porthcawl, Port Talbot, Neath, Swansea, and Llanelly. 
In order that the remarks which I have to offer may be brief and intelligible, I have 
prepared, from my own notes and the information supplied by the Geological Survey 
of Great Britain, seven sectional representations of the coal-fieid in the district alluded 
to, and shall at once refer to them for a description of the stratification. 
The base of our coal-measures is carboniferous limestone, which, it will be observed, 
is basin-shaped, having a general rise from its centre towards the north and south, 
to which all the coal-measures conform: and they may be described as consisting of 
the following convenient divisions :— 
; Black 
Mine. Bend. Coal. 
‘ Fi. In, In Ft, 
First,—The Farewell Rock or Millstone Grit, eliaeies 400 
no coal, and averaging a thickness Of .....+,sesssereseseeeees 
Secondly.—Argillaceous and arenaceous shales wie 360 36 
some beds of sandstones......sssseseeeserarereeees ey eae 
Thirdly.—Strata of a similar nature, containing several 
seams of coal, some of which are very thick, and associated 540 12 43 
with mine, and are extensively worked at all the great iron- wey 
WOLKS oeogerererseerecen ero sinepspanepeverne phcnsaopedsennes intr peneet 
Fourthly.—A similar stratification, but with some thick 
beds of quartz rocks, called the Cockshuts, particularly well 
seen along the anticlinal line between Cwm Avon and > 420 12 ade 3 
Maesteg, and regarded by the miner as sure guides to some 
of the accompanying rich coal beds ......sssseesessreeenees oe 
Fifthly.—Arenaceous and argillaceous shales, with oc- 
casional beds of sandstones, and containing black bands, 540 iF 11 
worked extensively at Cwm Avon and Maesteg, and lately 4 ~ 
discovered at the Ystalyfera Iron-Works ........+1++0+ Seems 
Sivthly,—A great accumulation of sandstones called the 
Pennant Rock, intermixed occasionally with some argilla- 3000 7 
ceous shale, represented in this neighbourhood by the Kil- a” ose 
vey and Town Hills, measuring 31) EDICKDESAS ascaherPerseas 
Seventh and last division, containing shales and some 3000 37 
thick masses of sandstone, and measuring about .,,...+.+-4 a ey 
Making a total average thickness of ...,..... seve 8260 60 386 JOL 
In this statement I have only included the workable seams of coal and mine, my 
object being to convey a correct impression as to the available portion of the South Wales 
coal-field; and in order that the geological arrangement of these divisions may be easily 
understood, I have distinguished them on the sections by various shades of colour. 
[The section was here explained. ] 
An important governing feature of the coal-field is the Pennant Rock, its outcrop 
being nearly as well marked as that of the carboniferous limestone. It may be traced 
in nearly its whole thickness from Swansea to Carmarthen Bay on the west, and east- 
ward towards Briton-Ferry, Margam, Llantrissent, round by Pontypool, back to Mer- 
thyr, and across the tops of the valleys to Pembrey, where it again disappears under 
Carmarthen Bay. 
On inspecting the Section No. 1, from Hirwain to Llantrissent, it will be observed 
that the lower portion only of this deposit caps the hills about the Rhonddas, and that 
it then bends over towards Llantrissent, accumulating the whole of its thickness, and 
bringing in the Dyhewydd seams, which may be considered equivalent to Hughes's 
seam, near Swansea, or to the commencement of the highest division of that coal-field. 
The denudation from the Rhondda of this thick deposit of sandstone removes, as it 
were, an impermeable cover, which, in other portions of the district where it is found 
to prevail in its full thickness, must serve as a seal to shut out for ever from the uses 
of man the lower thick beds of coal and mine so extensively worked along the margin 
of the coal-field; whereas, in this locality, they lie within an attainable depth for mi- 
ning, and as flat as can be desired by the miner. 
Day ont > 
