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at Gorsty Knoll in the Forest of Dean, Glos
1818/19 David Mushet built a coke-fired 'experimental furnace' at Darkhill. The larger part of the works was given over to research and experimental production.
1845 David Mushet retired and conveyed Darkhill to his three sons, with the youngest, Robert Forester Mushet, becoming the manager. Serious antagonism arose between the brothers
The site became derelict, but in recent times extensive work was done to investigate and stabilise the site. Many walls still stand, and stone sleepers of the tramway remain. However, the present ability to interpret the site at any time may be dependent on the encroachment of vegetation.
Close by are the remains of Robert Mushet's Titanic Steel and Iron Co Works. A few buildings remain, but these are not accessible to the public, and the owner's privacy should be respected.
A good overview of the Darkhill and Titanic Works was written by Keith Webb and published in 2001
More detailed information about the Darkhill Works may be found in the book 'The Industrial History of Dean' by Cyril Hart. From this we learn that in May 1845 the equipment included a blast furnace, a small cupola blast furnace of about 1000 cu ft capacity (it is not clear whether just one furnace was being referred to), a casting house, a bridge or filling loft, and office in the yard, a round boiler, and a blowing engine with a steam cylinder 24" dia and air cylinder 60" dia. Later that year the plant was augmented by two new cylindrical egg-ended boilers, two stoves for heating the air blast, a weighing machine, and various structural additions. The book also includes extracts from documents and letters written by various participants, including the Mushet's manager, J. Walkinshaw, which provide some insight into the technical difficulties encountered and also into the disagreements and antagonism which prevailed. A continuing problem was the inadequacy of the water supply for cooling the blast furnace tuyeres. David Mushet (Jnr) records 'a dreadful calamity, where three lives were lost through incompetence in the engineers'.
1846 'Explosion in the Forest of Dean, Gloucestershire.—A fatal accident occurred on Monday, July 27th, at the Darkhill Iron Works, near Park end, belonging to Messrs. Mushett. Two of the persons injured, George Powell, aged 28, and Herbert Powell, aged one year and ten months, died on the day of the accident; and" William Powell, aged 31, the father of Herbert, died on Thursday of the injuries he received. The wife of William Powell, and another child, and a man named Dobbs, were also much hurt. The force of the explosion was so tremendous, that the boiler, although weighing about three tons, was projected into the air perpendicularly, to the height of many feet, some of the witnesses believing at least 200 or 300. It came down precisely upside down, on the very spot from which it had been torn, while the lower part had been re- moved almost horizontally about the space of its own width. The steam pipes attached to the other two boilers were torn, and carried a very considerable height, as well as the stones, bricks, and other materials around. Inquests were taken on the bodies, when the jurors expressed themselves perfectly satisfied of the sufficiency of the boiler, with common care ; but there appeared reason to fear, that there had been inattention on the part of the unfortunate men themselves. From calculations made by Mr. J. Walkinshaw, sen., (of the Don Foundry, Doncaster,) the engineer, whose evidence was given in the clearest and most satisfactory manner, he arrived at the conclusion that a force equal to 4260 tons, or 9,242,400 pounds, would' have been requisite to have torn up the boiler, as it appeared to have been done, at one effort. This would give a pressure of 656 pounds per inch, far beyond any ever attempted, except with Mr. Perkins's steam guns.' 
1874 Advertisement: 'Severn and Wye Valley Railway and Canal - The Directors are prepared to receive TENDERS for the purchase and prompt removal of the materials of the Darkhill Blast Furnace, near Coleford. The iron work will consist of the boilers, blowing engine, piping, and all iron fittings connected with the furnace. The remainder will consist of stone and brickwork of the furnace and other buildings ; also the roofs and timber work of the engine-house, stables &c. Tenders to be sent in on or before the 14th March next, to the Offices of the Company, at Lydney, where any inquiries may be made.'