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Big Pit
(National Mining Museum of Wales)

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Geology - Coal Mining

The Coalfields
There are two coalfield in Wales: the South Wales Coalfield extending nearly 90 miles from Pontypool in the east to St Bride’s Bay in the West, and the North Wales Coalfield extending from the Point of Ayr south-eastwards to Hawarden and Broughton near Chester.

The South Wales coalfield is the larger of the two, being an elongated basin of Carboniferous rocks that are exposed as outcrops nearly all the way around its periphery. The basin has undergone much folding and faulting since the sediments were laid down and the effect of this was to bring many important coal seams closer to the surface. They would otherwise have been very expensive to reach and mine.

The old worksThe earliest reference to coal mining was for 1324 in the neighbourhood of Saunderfoot in Pembrokeshire. But it was not until the mid 16th century that the industry really became important. At first mining was done on a part-time basis by farm workers to supplement their income but soon the expanding industry required a dedicated work force.

The outcropping of coal seams along the edges of the Coal Field and along the sides of the valleys enabled the earlier miners to dig tunnels straight into the hillsides. Of course, before any coal can be removed from the solid seam of coal there has to be some system of preventing the unsupported roof from falling and injuring, or even killing, the miners. So in these workings, called levels or slants, coal was cut by the old, so-called, heading and stall system where the coal is removed from small areas along side the main tunnel, or roadway, with timber supports to help keep the roof from falling.

The old Welsh method of working coal was by pillar and stall, known in the 17th century as post and stall. Stalls or working places included the width of the roadway and a short length of coalface on one or both sides of the roadway. Stone above the roadway was removed and packed in the sides for extra headroom and support but in the stalls only the coal was removed. Here the original method was for the miner to remove a wedge of coal from the bottom of the seam, to a depth of three to four feet along the length of his stall - possibly up to 12 metres. Short props held up the coal while the mine cut his way along the seam. Then he would knock them out and the coal would fall. The coal was mined by hand - sometimes assisted by pneumatic pick or even controlled explosives. The coal was loaded into trams and pushed out on iron rails until it could be hauled out by horse or powered rope.

To recover coal from deep below the surface shafts to be sunk, sometimes to depths of up to about 780 metres, and roadways dug outwards into the most profitable coals. Winding houses were built to contain the engines that lowered and raised the cages of men and wagons of coal and the headframes, with their characteristic pair of winding wheels, sat on top of the shafts. The roofs of the roadways dug into the coal were supported by wood and then later by iron and steel supports.

The introduction of coal cutting machinery during the second half of the 19th century led to the widespread use of the longwall system where faces 200 metres, or more, were cut and often serviced by roadways on either side. At first the cut coal had to be removed by hand but conveyors were then introduced to carry the coal away from the face to trams in the roadways. The development of flexible armoured conveyors brought in a rapid increase in mechanisation. Now the cutting machine travelled continually along the face, cutting and loading coal onto the conveyor and as it passed the conveyor was pushed against the newly cut face by hydraulic rams. In the longwall system the roof was only supported for several metres behind the advancing face, leaving the unsupported roof further back to fall. Wooden pit props were used for this purpose until the early 1950s when hydraulic props were first introduced. Advances in techniques quickly led to sets of two and even four hydraulic propos with rams in their bases attached to the armoured conveyor resulting in a powered, self-advancing support system that revolutionised coal-mining.

In 1855 the output of the South Wales Coalfield had been approximately 8.5 million tons, but by 1913 it had reached its peak of approximately 57 million tons, or a fifth of the entire output of the United Kingdom. Then there were 620 coal mines employing 232,000 men. During this period of unprecedented expansion the industry needed an ever-increasing workforce and people flocked to the area in response. Most left their rural ways of life and came instead to the teeming, seemingly prosperous valley town. Fortunes were made by the few, but for most of the mining families life was very hard, with housing being often primitive and in short supply. Families were usually large and lodgers were common. Expansion ultimately came to an end and then coal production gradually fell to 45 million in 1930, 35 million in 1939 and 20 million in 1945. It increased to 24-25 million until1957 when it fell again. By 1975 the output was approximately 8.5 million again with 42 mines employing 30,800 men. Now there is only one deep mine still operating, Tower Colliery at Hirwain, which produces about?? tons of coal a year.

Nearly all the signs of this once thriving industry have disappeared. Surface buildings of the collieries have been demolished, the shafts capped and the waste tips landscaped or even removed. Of the few that are left, Big Pit and Lewis Methyr at the Rhondda Heritage Park are best and they are both open for visitors.


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