BEYAN — OX THE SOUTH WALES COAL-FIELD. 



91 



canse of this, we are told,* has been a strong lateral pressm^e, acting 

 nneqnally, or meeting with unequal resistance, after the accumulation 

 of the Old Red Sandstone, and probably of the Coal-measui^es, 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 dificult for the stranger to ascer- 

 tain his whereabouts ; but this applies more particularly to Mon- 

 mouthshire. From the table-land of millstone-gTit 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 Fa^\T (Little and Great Ebbw), succeeded by 

 the Sirhowy and Bhymney 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 directions : first, that of the Taff with its 

 feeders of Aberdare and Bhondda, 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 Og'wr, 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 Yale 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 Yale of Neath we have that of the Tawe 



* Memoirs of the Geological Survey, vol. i., page 224. 



