By 1850, new methods of coal mining had been developed so that deeper coal seams could be exploited. The building of a network of tramroads improved transportation problems to such an extent that by the mid-nineteenth century the iron masters turned towards coal production.
By 1839, when the Bute Docks were opened in Cardiff, coal was conveyed from many pits in the area by tramway to the Glamorganshire Canal which had been opened in 1794 to transport iron from Merthyr to Cardiff. Tonnage figures indicate that mining on a big scale had begun and was of such importance that in the year 1841, a Branch of the Taff Vale Railway was opened from Llancaiach. Eight locomotives were used on the Taff Vale Railway to convey coal and iron to the sea and it is of interest to note that one of them was called " Llancaiach ".
In the Rhymney Valley the first industrial landmark was the opening of the Rhymney Tramroad in 1826. This tramroad ran from Rhymney to Newport on the Monmouthshire side of the valley and was intended chiefly for the transport of iron from Rhymney to Newport. Soon it was found, however, that by the construction of short tramroads over the river, it was possible to mine the coal on the Glamorganshire side and send it also to Newport.
Thomas Powell was one of the first to make use of the Rhymney Tramroad. He was familiarly known as "Powell of the Gaer," after his residence in Newport, where he had begun his commercial career as a timber merchant. He owned the Gelligaer Level as well as mineral leases on both sides of the Valley and by 1839 was one of the foremost exporters of coal from the district. Later he entered the Aberdare Valley where he proved the Four Foot Seam and then became the leading coal exporter in south Wales, if not the World.
Cil-haul Tramway ran from the engine house, which was located just below the crossroads at Pentwyn, to what was the site of Ogilvie Colliery (previously called Cil-haul Colliery OS 1884). The tramway passed under the B & M Railway following a very steep descent to the bottom of the valley.
The Effect of the Railway on Mining.
In anticipation of the opening of the Rhymney Railway, there had been a rush to obtain coal leases from the owners of the land adjoining it, and by 1860 there were twelve collieries in operation.
Development of coal mining in Fochriw and Deri was made possible by the extension of the Rhymney Railway from Bargoed to Deri, the Brecon and Merthyr Railway from Pant to Deri with a connection to Fochriw colliery, and the opening of the GWR/Rhymney Joint Railway in the Taff Bargoed Valley which gave a second connection to the Fochriw colliery