60 Transactions of the 



are the Vale of Neath, the Llynir Valley, Ogmore Valley, Ely 

 Valle}^ Ehondda, Ehondda Fach, Aberdare, Taff Vale, Khymiiey, 

 and Ebbw, up all of which run railways of the same names as the 

 valleys they traverse. In addition to these, the following railways 

 may be mentioned — the Sirhowy and Eastern and Western Val- 

 leys Railways. Cardiff, Newport, and Swansea are the three chief 

 ports from which the coal is shipped. 



The extent of the South Wales coal-field (that is, of coal-pro- 

 ducing strata) is, from Blaenavon and Pontypool on the eastern 

 outcrop to St Bride's Bay, Pembrokeshire, on the west, a length 

 of about ninety miles ; while the width varies greatly from the 

 north to the south outcrop, being, in Monmouthshire and Gla- 

 morgan up to the river Loughor (the county boundary with Caer- 

 marthenshire), about sixteen miles (in this is included the small 

 area lying in Brecknockshire) ; from the Loughor river to Kidwelly 

 and Caermarthen Bay about ten miles ; under the bay to Saunders- 

 foot about five miles ; and from Saundersfoot, through Pembroke- 

 shire to St Bride's Bay, an average width of four miles. 



The superficial area of the entire coal-field is about 937J square 

 miles, or G00,000 acres ; the average thickness of the pure coal 

 being about sixty feet (that is, placing all the different seams to- 

 gether horizontally and measuring them in section), while the 

 amount of coal yet obtainable from the coal-field cannot be less 

 than about thirty-six thousands of millions of tons. 



At its eastern end the coal-field is bituminous, but from 

 Cyfarthfa to Mynydd Mawr and Grwendraeth it is anthracite. 

 Bands or seams of argillaceous ironstone are also found in many 

 of the collieries, of which Skyboraven Colliery, near Aberdare, may 

 be taken as an example. These bands of ironstone, taken in the 

 aggregate, are about seventy inches thick in horizontal section, 

 and make the finest foundry pig-iron, bars, and rails in the world. 



The dip along the north outcrop of the South Wales coal-field 

 is very moderate, ranging from three to six, and, in some cases, 

 nine inches per yard, while, on the south crop, it varies from nine 

 to twelve, fifteen, and eighteen inches per yard, the beds gradually 

 flattening northwards, and leaving a large area in the centre of the 

 field comparatively level, excepting where the anticlinal line dis- 

 turbs the stratification. Even adjoining that, however, the dip 

 varies very much. The most numerous 'faults' of the field run 

 from north-west to south-east, and vary in amount of vertical dis- 

 placement up to 750 and 900 feet. Others run in an east and 

 west direction, being in some places from 1200 to 1500 feet. The 

 largest fault in the field is in Pembrokeshire, and this is as much 

 as 2000 feet in vertical displacement. There are two ways of 

 getting at the coal practised in South Wales — one, the common 



