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Site of Plymouth Ironworks/Trevithick Tunnel

Site of Plymouth Ironworks/Trevithick TunnelAlthough the name of the Plymouth ironworks is synonymous with the Hill family, it was in fact founded by others involved in the early history of iron making in Merthyr Tydfil. In December 1763 Isaac Wilkinson of Plasgruna near Wrexham and John Guest of Broseley, Shropshire, leased a large area of land on the east bank of the River Taff below the village of Merthyr from the fourth Earl of Plymouth.

The deed showed that they wished to build “certain ffurnaces, fforges, Mills, pothouses, or other Works for the making and manufacturing of iron”. They were also permitted to dig, raise, and carry away coal or iron under the land. They chose to build a small furnace on the banks of a tributary of the Taff, which flowed from the hills to the northeast, but there is no evidence that it ever went into production.

Despite the location’s obvious potential, it seems that problems with the existing tenants of the property discouraged the partners and they sold their rights to Anthony Bacon, an ironmaster who was already involved with developments at Hirwaun and Cyfarthfa.  On Anthony Bacon’s death the works was left to his son Thomas who was then under age. So in 1786 the Court Of Chancery granted a lease of the Plymouth Furnace to Richard Hill who had been Bacon’s agent at the Cyfarthfa works.

Site of Plymouth Ironworks/Trevithick TunnelWhen Richard Hill took over the works it consisted only of ‘one small furnace worked by two giant bellows twenty-five feet high and one large waterwheel’. It is probable that the original supply of water came from the adjacent stream later to become known as Nant Cwm Blacs. After acquiring two partners and additional capital in 1803, Hill was able to expand the enterprise with the construction of a second furnace. As the works grew the tramroad network which linked it with the various pits and levels also expanded.

The coal and ironstone came at first from the hillsides immediately above the works, necessitating the building of inclines, which would have brought the raw materials to where they would have been prepared before being loaded into the furnace. The means by which the works acquired water to power its machinery was also improved with the construction of a large weir across the River Taff at Merthyr. Water was then channeled through an open feeder through the Caedraw area of the rapidly developing town, to the works site.

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