BEVAN — ON THE SOUTH WALES COAL-FIliLD. 
91 
cause of this, wo are told,* has been a strong lateral pressui-e, acting 
unequally, or meeting with unequal resistance, after the accumulation 
of the Old Red Sandstone, and probably of the Coal-measures, the 
effects of which are principally seen in the counties of Pembroke) 
Caermarthen, Glamorgan, Monmouth, Brecon, Hereford, and Wor- 
cester ; and not only has this pressure conduced to the outward 
shape of the basin, but, as we shall presently see, to the peculiar 
troughs and anticlinals within the basin. 
Over the greater portion of the district, hill and dale succeed each 
other with wonderful regularity, causing one valley to resemble the 
other so much that it is frequently difficult for the stranger to ascer- 
tain his whereabouts ; but this applies more particularly to Mon- 
mouthshire. From the table-land of millstone-grit and limestone on 
the north, issue a number of small streams running due south to 
the Bristol channel, at an interval of from four to six miles. From 
east to west we have first the valley of the Afon, followed by those 
of the Ebbw Fach and Fawr (Little and Great Ebbw), succeeded by 
the Sirhowy and Rhymney rivers, all of which converge, and have 
their outlet at, or near Newport. We then cross the Taff into Gla- 
morganshire, where a change takes place in the physical features. 
There are still valleys and hills, but the valleys are broader and of 
more importance, while the hills are more irregularly placed, and 
grouped in more picturesque fashion. We have now two sets of 
valleys running in different dii-ections : first, that of the Taff with its 
feeders of Aberdare and Rhondda, finding their terminus at Cardiff; 
but west of the Taff we find ourselves in the most mountainous 
portion of Glamorganshire, in which the hills are of great height, and 
the valleys become mere dells : the principal of this set are the 
Llynvi, the Ogwr, and the Afon, the two first of which find their 
outlet at Bridgend, and the latter at Aberavon. Secondly, turning 
to the north, we find that from the same table-land which gives birth 
to the Aberdare valley, issues the beautiful Vale of Neath, running 
to the south-west, an important alteration in the physiognomy of 
the county. All the subsequent rivers follow nearly the same ar- 
rangement ; for west of the Vale of Neath we have that of the Tawe 
* Mcnioii's of tlie Goulogical Survey, vol. i., page 224. 
