160 Bevan— Coal-basin of South Wales. 
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Fig. 3.—View of Ebbw-Vale, looking due South, from above Beaufort ; showing the character of 
the river-valleys and the Pennant Hills. 
4, The Rhymney Valley, with its subsidiary, the Bargoed Valley, 
has its outlet near Cardiff. 
5. The Taff Vale, from Merthyr to Cardiff, with its feeders, the 
Bargoed Taff, the Cynon, on which river the important ironwork 
town of Aberdare is situated, and the Rhondda Valley, which joins 
the Taff at Pontypridd, and runs from thence in a north-westerly 
direction towards the Neath Valley. 
So far there is a striking parallelism and uniformity in all these 
valleys ; but after crossing the Taff we find the country more dis- 
turbed, and the physical features altered. ‘This is principally owing 
to the Vale of Neath, which, though rising in the same horizon, and 
indeed not far from the Taff, takes a west-south-west direction to 
the sea. The triangular district thus formed is watered by streams 
of shorter course and smaller volume, such as the Ogmore, the 
Llynvi, and the Afon, which flow through much more contracted 
valleys. But the Neath Valley once past, the parallelism is re-esta- 
blished; the Tawe, the Lloughor, and the Gwendraeth Rivers flowing 
tolerably due south, to enter the channel at Swansea, Lloughor, and 
Kidwelly respectively. So much for the river-valleys. If we take 
the long axis of the basin, we shall find two depressions intersecting 
the river-valleys at right angles: 1. The one described as the 
‘North crop ;’ and, 2. A more important one, commencing at Ponty- 
pool, and running past Crumlin, Newbridge, Blackwood, and 
Quaker’s Yard, where it is deflected to the south; as faras the latter 
place, the Great Western Railway has seized it as vantage-ground 
to tap the centre mineral district, and to reach Merthyr and Aber- 
dare. I have given these features somewhat in detail, as it is neces- 
sary to bear them in mind when speculating on the cause of the 
arrangement. Sir Henry De La Beche, in his masterly résumé of 
the Formation of Rocks in the South-West of England (‘ Memoirs, 
Geological Survey,’ vol. i.), points out that a tremendous force has 
