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Herland Mine
Gwinear, Cornwall, UK
associated engineer
Richard Trevithick
date  circa 1717-78, 1790-1808, 1815-16, 1824-43, 1854-74
era  Georgian  |  category  Mining/Quarrying  |  reference  SW589370
Herland Mine was the name of a group of mines, sometimes known locally as Manor Mine, characterised by narrow but rich veins of copper. The mine operated intermittently for almost two centuries but is now abandoned — its site boundaries are no longer discernable and little remains of the surface buildings.
The Herland lodes had been worked for their copper since at least 1717, and probably before that. The first record of a grant to drive an adit, or drainage tunnel, through the mine workings was in 1726. The mine covered an area some 1km long from north east of Drannack Mill to south of Gwinear.
By the 1750s, workings at Manor Olde Lode were 219.5m deep, and the mine was being pumped out by a Newcomen engine with a 1.78m diameter cylinder installed in 1756. The mine then comprised Manor Olde Lode and North Herland. It continued operating until 1762, with ore sales until 1778.
The mine was open again by 1790 but its productivity was hampered by insufficient pumping effort to enable dry working at deeper levels. In 1791 Wheal Fancy, Wheal Pleasure and Old Herland were added to the mine’s ‘sett’ — its mineral extraction boundaries. The mine managers bought a second-hand Watt engine with a 1.63m diameter cylinder from Wheal Busy (SW739448) in Chacewater to drain the now much larger mine.
By November 1791, the new engine house was completed at Old Herland and the engine’s boiler was almost finished. The engine was steaming the following year and by July 1792 North Herland was dry, Old Herland had been drained to 91m below the adit and the nearby Prince George Mine to the south east was also drying out. However, the porous rock strata of the mine meant that pumping was a more costly and time-consuming venture than anticipated — not helped by heavy rain.
By December 1794, a Bull pumping engine with a 1.52m diameter cylinder had been fixed over the shaft at Wheal Fancy. In 1795 a third pumping engine was installed, this time a shammal engine with a 1.02m diameter cylinder bought from Godolphin Great Work Mine (SW596307).
In 1797 a whim, or winding, engine was set to work — previously all winding at Herland had been done with horse whims. The engine was a Boulton & Watt rotative steam engine with a 460mm diameter cylinder, originally used at Wheal Maid (SW742423) in Gwennap. In 1798 a fourth pumping engine and a second whim engine were being erected at Herland.
Between 1792 and 1798, the price of copper was low but the mine also produced zinc and some tin. Then in 1798-9 localised deposits of silver ore were discovered 219m below the surface.
By 1799, the mine workings were 274m deep. However, the Napoleonic Wars (1799-1815) and consequent rising costs of materials caused the lower levels of both the Herland and Prince George mines to be abandoned in 1801. Work continued at higher levels until 1808.
The mine re-opened in early 1815. Richard Trevithick (1771-1833) had achieved astonishing results with his high pressure steam engines at other Cornish mines — they proved far more efficient than the low pressure and atmospheric engines used at the end of the 18th century. He had invented the plunger pole engine in 1810-12 and installed the first at Wheal Prosper (SW588406). Now he built one at Herland.
The engine had no rocking beam, as the steam cylinder was mounted vertically above the mine shaft. The piston, or plunger pole, was connected by crossheads to the pump rods below and moved by the expansive power of the high pressure steam from the boilers. The plunger pole engine was described in the first part of Trevithick’s patent (no. 3922) for high pressure steam engines dated 6th June 1815, with additions on 20th November the same year.
On 8th July 1815, Trevithick wrote to his mentor Davies Giddy (1767-1839, known as Davies Gilbert from 10th December 1817) that “Woolf’s engines is Stop’s at Herland and I have orders to proceed”. Rival engineer Arthur Woolf (1766-1837) erected a compound engine of his own design at Wheal Vor (SW624303) near Breage in 1815, but it is not clear whether his engine at Herland was already in place or merely on order.
Trevithick’s engine had a 840mm diameter cast iron plunger pole, working a 3.05m stroke and driving a 370mm diameter pump. The top of the plunger pole when at rest was level with the top of the shaft. The steam vessel was 1.22m in diameter and, like the pole case, was made from 19mm thick wrought iron.
There were two boilers, each a tube 13.72m long and 910mm in diameter made from 13mm thick riveted wrought iron plates. They were heated by a fire beneath them, which returned heat over the tops — probably via a flue that then led into the chimney. The boiler tubes were 380mm higher at the steam end and had two 100mm diameter valves, one for steam and one for discharge.
The engine and its housing cost £700, comparing favourably with Woolf’s engine at Wheal Vor costing £8,000 and taking two years to complete. Trevithick’s engine began pumping in February 1816, operating at pressures between 414 and 827kN per square metre.
On 11th February, he reported to Giddy that it been working a slightly longer 3.2m stroke, three quarters of it expansively, at 12 strokes per minute. On 15th February Giddy calculates that the engine’s duty was 57.75 million. Independent examiners, assessing the engine on a 3.05m stroke at 20 strokes per minute with the steam cut off at one-sixth of the stroke, reckoned its duty as 48 million. The highest duty that the much larger 1792 Watt engine achieved was 27 million.
Trevithick and engineer William Sims (1762-1834) later added pole cases to existing Watt engines at several Cornish mines and the resulting compound engines showed much increased duties.
However, the high pressures used in the pole engines began to show the deficiencies of its design, and the limitations of the manufacturing techniques then available. It was difficult to maintain heat over the large surface area of the pole exposed on each stroke, its middle wore more quickly than its ends and the packing between pole and case (cylinder) tended to work loose. Also it was hard to keep the riveted boiler joints steam tight at high pressure and the escaping steam could be seen and heard for some distance.
Financial difficulties and mismanagement resulted in the closure of the mine in autumn 1816. The machinery and materials were auctioned in November that year.
Herland was a working mine again in 1824 and, though yielding ore, was making a loss. Production increased up til 1832 but then declined, and in 1838 its pumping engine (2.03m diameter cylinder) and two steam whim engines (both 410mm diameter cylinders) were sold. The mine closed in 1843, by which time it had raised 18,800 tonnes of copper ore and accrued sales worth £159,074 since 1816.
In 1854, Herland Mine joined with nearby Rosewarne Mine to the east. The amalgamated mine worked until 1874, under the name Rosewarne & Herland United.
Herland Mine’s total recorded output was 33,500 tonnes of copper ore, 175 tonnes of tin ore, 158 tonnes of silver ore and 112 tonnes of zinc ore.
Research: ECPK
bibliography
“A History of Copper Mining in Cornwall and Devon” by D.B. Barton
D. Bradford Barton Ltd, Truro, 2nd edition 1968
“Mines and Miners of Cornwall, Part V: Hayle, Gwinear and Gwithian”
by A.K. Hamilton Jenkin, Truro Bookshop, Truro, 1963
“Richard Trevithick: the engineer and the man” by H.W. Dickinson and Arthur Titley, Cambridge University Press, London, 1934
“Life of Richard Trevithick, with an account of his inventions”
by Francis Trevithick, E. & F.N. Spon, London, 1872
www.gracesguide.co.uk
www.mindat.org
Location

Herland Mine