Site of Plymouth Ironworks/Trevithick Tunnel
Although 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.
When 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
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.