Mona Mine Records (Plas Newydd Papers)

Scope and Content

A collection of 3770 items (many of them consisting of bundles of papers not individually described), relating to the Mona Copper Mine on the slopes of the Parys Mountain near Amlwch in north-western Anglesey. The collection ranges in date from 1764, when the first considerable strike of copper ore was recorded, to 1878, by which time the productivity of the mine had long been in decline, and includes papers illustrating the working of the mine under the successive dispensations of Sir Nicholas Bayly of Plas Newydd, 1764-1785; the Earl of Uxbridge and Thomas Williams of Llanidan, 1785-1802; and the (first) Marquess of Anglesey, 1817-1854. Apart from the various accounts and returns (including those of labourers and ore-breakers, shipments, bargains set and settled, etc.) covering every aspect of the mine's activities, there are also many hundreds of letters addressed to the three successive mine agents: John Sanderson, Thomas Beer and F. A. Legg between 1817 and 1878 and dealing with such topics as the crises of the pre and post Waterloo years, day-to-day problems of management and production, new developments in smelting, fluctuations in the market, relations with the adjoining Parys Mine and complications over the working of joint levels and precipitation pits, vicissitudes of freight and carriage, transactions with brokers, exporters and manufacturers and the depression which set in after 1848.

Administrative / Biographical History

Parys Mountain on Anglesey was in the eighteenth century divided into two farms, Cerrig y Bleiddia Farm on the eastern side owned by Sir Nicholas Bayly, and Parys Farm on the western side which was held in moiety by Bayly, aforementioned and William Lewis of Llysdulas. The mountain had remained comparatively idle and unproductive since the beginning of the seventeenth century, although its possibilities hadn't been wholly forgotten. In 1762 however, Alexander Fraser, a native of Scotland, induced Sir Nicholas Bayly, the proprietor to sink shafts in the mountain. Copper ore was discovered, but not a sufficient quantity since the shafts became flooded and the enterprise had to be abandoned. Consequently, Sir Nicholas Bayly insisted that Messrs Roe and Co. of Macclesfield, lessees of Penrhyn Du in Llanengan parish also take that white elephant, Parys Mountain, off his hands for 21 years. They did so with great reluctance, and although they found ore, after years of expenditure with no profits they resolved to discontinue operations. They were about to give up in despair when, as a last resort they sent for their foreman from Penrhyn Du, Jonathan Roose, a Derbyshire man. A spring directed him to the spot for sinking and he divided the workmen into partnerships of three or four apiece and ordered them to sink shafts in several places, within about seven to eight hundred yards of the spot. It was one of these groups of bargain-takers that first struck ore on 2 March 1768. Seven years after this 'lucky strike', further discoveries were made to the west of the original workings, by the Rev. Edward Hughes, who had become co-owner with Sir Nicholas Bayly through his marriage to the daughter of William Lewis. In order to disentangle his claims from those of Sir Nicholas Bayly and to work his ores independently, the Rev. Hughes employed the services of a rising local attorney, Mr Thomas Williams, whose fortunes were henceforth to be inextricably bound up with those of Parys Mountain.

Mr Thomas Williams was the son of an Anglesey farmer who had worked up a practice for himself at Beaumaris. He is responsible for inducing Sir Nicholas, through the services of a London banker, to grant a lease of his moiety of the joint estate to a partnership consisting of the Rev. Hughes the co-owner, Mr Davies the banker and Mr Thomas Williams the legal adviser and business manager. This was the origin of what became to be known as the Parys Mine Company.

From here onwards mining work went rapidly ahead. In 1785 the lease of Roe and Company had run its 21 years, and instead of renewing it, the Earl of Uxbridge, who had now succeeded to Sir Nicholas Bayly's estate, followed the example of his neighbour and formed a company of his own, which became known as the Mona Mine Company. Again, the chief agent and principal partner after the Earl himself, was Mr Thomas Williams. The Mona Mine Company was designed as a close parallel to the Parys Mine Company. While the companies were independent in form, there is no doubt that they were run by Williams. Under Thomas Williams the works began to flourish and by 1785 they were supplying not only the British Navy, but also those of France, Holland and Spain, with copper bolts, nails and sheathing. He claimed in 1799 to be conducting half the copper industry of the country, with a capital not far short of a million, and a coal consumption of 750 chaldrons a day.

In 1811 a new company took over the Mona Mine and introduced James Treweek as manager. He is the most important figure in the history of the mines in the nineteenth century, and is second only to Thomas Williams in the whole story of their development. The Mona Mine papers show clearly the importance of James Treweek's role in the industrial development of Amlwch during the first half of the nineteenth century. The death of Treweek in 1851 marked the end of an era in the history of the Anglesey copper industry. The decline that was evident before his death was accelerated during the second half of the nineteenth century, until the mines and smelting works were closed down. No other person took control who had the qualities or ability of either Thomas Williams or James Treweek.


Arranged according to subject then chronologically.

Access Information


Open to all users

Acquisition Information

The first deposit was made by the sixth Marquess of Anglesey, ca.1945. Six other deposits were made in December 1946, May 1947, July 1947 (two desposits), September 1948 and February 1949.

Other Finding Aids

Two catalogues at item and series level

Separated Material

Grenfell Manuscripts at the University of Wales Swansea See index of National Library of Wales Handlist of Manuscripts, Volume IV, under 'Mona Smelting Works'.

Conditions Governing Use

Usual copyright conditions apply. Reprographics made at the discretion of the archivist.


None expected

Related Material

Bangor Manuscripts 880, 1516, 3010-3032, 15366, 31584-31626A, 31652-31685 (Mona and Parys Mines), 1783-1793 Plas Newydd Manuscripts Llysdulas Papers Kinmel Mauscripts


Dodd, A. H., 'Parys Mountain During the Industrial Revolution', Anglesey Antiquarian Society and Field Club Transactions, 1926, pp. 90-105. Cockshutt, E., 'The Parys and Mona Copper Mines', Anglesey Antiquarian Society and Field Club Transactions, 1960, pp. 1-25. Rowlands, John, 'Cornishmen at the Amlwch Copper Mines', Anglesey Antiquarian Society and Field Club Transactions, 1963, pp. 1-15. Lewis, Samuel, A topographical dictionary of Wales, comprising the several counties, cities, boroughs, corporate and market towns, parishes, chapelries, and townships, with historical and statistical descriptions: embellished with engravings of the arms of the bishoprics, and of the arms and seals of the various cities and municipal corporations: and illustrated by maps of the different counties in two volumes, (3rd ed, London, 1845). Harris, John Raymond, The copper king; a biography of Thomas Williams of Llanidan, (Liverpool University Press, 1964). Rowlands, John, M.A, Copper Mountain, (Llangefni, Anglesey Antiquarian Society, 1966). Richards, Thomas 'Mona Mine Letters', Anglesey Antiquarian Society and Field Club Transcations, 1946, pp. 80-91. Access Points