During the late medieval period the mining of silver-bearing ores effected a transition from a handicraft form, based on the activity of independent miners, governed by custom and with the minimum of royal involvement, to a capital intensive industry subject to central management in which the miner was an employee of the Crown or its lessees. After 1500 new centres of silver mining were opened up in mid wales and in the south-west of England, where earlier (medieval) sites like Combe Martin were reopened and proved particularly productive.
At their conquest of England in 1066, and the subsequent occupation of parts of Wales, the Normans inherited a dispersed, small scale silver mining industry exploiting silver bearing lead ores. The mines were to be found on the Carboniferous limestone uplands like the Derbyshire Peak, Mendip, the Welsh borders and the northern Pennines where shallow enriched ore deposits had escaped the effects of glaciation. Deeper seated deposits in the pre-Carboniferous rocks, particularly in the South-West of England which escaped the full effect of glaciation, were not exploited until the latter part of the 13th century and it was the mines of Tynedale and upper Weardale in the northern Pennines which provided the peak of English silver production in the mid 12th century.
Prior to the thirteenth century the ownership of silver bearing ores resided with the lord of the soil. The English Crown sought no greater control over production than its right of lordship over the principal sources, in the liberty of Tynedale, allowed and was willing to relinquish control of resources in a grant of lordship, as was the case with the bishop of Durham's lordship over the upper Weardale mines. It was only in mid 13th century that regal authority was extended to a prerogative on silver-bearing ores although the Crown respected existing rights, culminating in the direct working of the Devon mines in 1292.
Working of the Tynedale mines - the Mine of Carlisle - of the 12th century was in the hands of the miners themselves. Governed by custom the miners were largely self regulated, paying a portion of their produce - one ninth after tithe - to the Crown as lord. The income generated being leased to local collectors who accounted for the farm to the sheriff in Carlisle who record it along with other farms for the county of Cumberland. Thus the Crown took no direct part in the production of silver, relying on its right of pre-emption to direct silver to the mint. When, in the late 13th century, the Crown took control of new centres of production in Devon it chose to operate them using a directly employed work force - some of which it impressed in the customary lead fields of Mendip, north-east Wales and the Derbyshire Peak, later supplementing them with tinners from the Stannaries - supervised by Crown officers. The Devon mines - centred on those at Bere Ferrers - were worked in that manner for a little over fifty years.
By late 14th century the problems of increasingly deeper working of the silver deposits in Devon were exacerbated by the rapid demographic decline during the plague years. Mining ceased in about 1350 and when reopened in 1360 the Crown chose to lease them on a county basis, withdrawing totally from direct working. Mines were generally worked by or on behalf of the lessee and only occasionally, as at Bere Ferrers in the 1450s, were discrete sections of the workings sublet to individuals or small partnerships. The form of the lease, applied across England, was developed during the 15th century to include all those elements found in its modern counterpart - royalties, dead rent and a fixed term.
Most of the mining, and preparation / smelting, techniques in place at the end of our period had been employed before the 11th century. Their use in the late medieval period reflected the demands of silver mining and the availability of resources, both material and human. Working the shallow deposits exploited prior to the late 13th century involved surface trenches and shallow levels, requiring only limited drainage.(1) Within five years of opening up the Devon mines adits were introduced to meet the drainage requirements of deeper working. The continuing need to supplement this with manual water haulage and the increased cost of labour, attending demographic decline, stimulated the introduction of mechanised pumping by 1480. Both smelting and refining responded too to the availability and cost of labour in the choice of motive power. The smelting techniques, introduced into Devon from the lead mining fields, were adapted through experimentation in the late 13th / early 14th century to allow the processing of all the ore mined - resulting in the bole / furnace complex which satisfied the industry until superseded by new technology in the 16th century.
Increasing use of coin for commercial transactions during the late medieval period ensured that the demand for silver was sustained. However, the part played by newly mined English silver was overshadowed by that entering the country as coin or bar in payment for growing exports - wool and, later, textiles. With an estimated mint production of £125,000 during 1158-80, silver from the northern Pennines made a significant contribution. But the fall in production during the 1180s left England without a reliable source and the subsequent, and substantial, increase in mint output over the next two decades was fuelled by imported silver. The opening of the Devon mines in 1292 provided some respite. Coin in circulation had increased fourfold, to around £1,000,000, by the early 14th century and against this we have to set the peak annual output from the Devon mines of less than £2000. Production from these mines did not, as the antiquarians would have use believe, finance the wars of Edward I and III.
Whilst the quantity of silver produced during the 12th century can be estimated with some confidence we do not know the precise location of the workings. Neither can we be certain as to the nature of the ores worked, where they were processed, nor the quantity lead which might have been produced as a by-product. Information is available on the organisational structure under which mining was carried out but there is currently little to indicate how it fitted into the social framework and upland agricultural practice.
Resolving these problems requires further co-operative research by geologists / mineralogists, archaeologists and local historians. With this in mind, a seminar to discuss the options for further work is planned for the Spring of 2005.
At the close of the medieval period the vast majority of manufactured and primary output in England came from small producers integrated into rural society. Mining has, in the past, been excluded from such a model by historians holding a view, coloured by post-medieval developments in certain sectors like copper and coal production, that its demand on capital and techniques was beyond the reach of the small producer (4). Burt and others (5, 6, 7, 8 and 9) have, however, argued convincingly for its inclusion; seeing the archetypal mine at the close of the medieval period as small scale, supporting increased production through a multiplicity of similar small operations. It created no great demand on either capital or technology and its workforce was integrated into its landscape, moving easily between agriculture and mining in tune with demands on production.
There was, neverthless, one sector of non-ferrous metal mining which had developed on a large, capital intensive, ‘industrial’ scale from the 13th century. The mining of silver-bearing ores was, prior to the 13th century, largely centred in northern England, regulated according to custom which allowed the participation of a multiplicity of small operators, and exploited rich shallow resources (see Claughton 2003b). When, in the 13th century, the English Crown exercised a right of prerogative over silver-bearing ores and opened up mines in Devon, mining in this and later silver mining fields was divorced from customary regulation. In doing so the Crown embarked on a course of action which was unprecedented and not emulated in continental Europe until at least the 17th century.
The principal silver producer, at Bere Ferrers on the confluence of the rivers Tavy and Tamar in south Devon, was worked under the direct management of Crown officers from 1292 to 1349; a practice continued beyond that date by Crown lessees. Over 300 men were employed on wages and piecework, many being pressed into service and moved to Devon from other mining fields. By the early years of the 14th century a programme of capital expenditure on development was in place, taking the workings well below the water table with a requirement for well planned drainage. Processing of the ores mined was carried out at a number of sites around Bere Ferrers including a complex of smelting and refining furnaces at Calstock, on the Cornish bank of the Tamar, although subsequent developments in furnace technology led to a concentration of both smelting and refining in a water-powered ‘fynyngmyll’. The demand for timber in the mines, and as fuel for the smelting / refining processes, meant that woodland was exploited in a wide area around Bere Ferrers. Water transport was used to supply the mines and smelting sites with necessary expenditure on boat repairs; and a ropeworks was established to satisfy the requirements for haulage within the mines.
A continued demand for silver, particularly during the bullion crisis of the mid 15th century, encouraged deeper working of the Bere Ferrers mines. The attendant high costs in manual drainage stimulated the introduction of innovative mechanised pumping by 1480, along with the associated leat system to feed its water wheel. However, by 1500, the accessible silver-bearing deposits were worked out. The nature of the mineralisation, and the ability of the medieval miner to work at considerable depth, meant that it was not until the introduction of steam-powered pumps in the 19th century that modern miners could drain the old workings and exploit deeper deposits to the south under the River Tamar.
Recent work on the economic and social history of silver mining (2) has identified the organisational and technological changes affecting the Bere Ferrers mines. In the course of that work many aspects of mining were identified which could not be satisfactorily explained by the surviving documentation. In addition some physical features were noted which supported the documentary evidence but require further investigation.
A landscape archaeology study has been used to resolve some of the outstanding issues and identify sites for further investigation. The Bere Ferrers Project was funded by the Leverhulme Trust, carried out by the Department of Archaeology at the University of Exeter, and the results will shortly be published by the University of Exeter Press as Mining in a Medieval Landscape: The Royal Silver Mines of the Tamar Valley. More details are available on the Project web pages.
It is the continued working of silver-bearing ores at Combe Martin which is the current focus of research; building on the investigation carried out into lead smelting residues from the 16th/17th century and the presence of mineral coal amongst those residues (11).
At the close of the medieval period lead/silver smelting relied entirely on organic sources of fuel - brushwood in the wind-blown bole hearth and charcoal in a series of bellows blown furnaces. During the latter half of the 16th century a new process, the wood fired ore hearth, was developed, probably on Mendip, and diffused quickly to other lead and silver mining fields in Britain. The advantages of the ore hearth, with its controlled roast/reduction chemistry allowing for the efficient smelting of a greater range lead based ores, led to the demise of the bole although some charcoal fired furnaces were retained for the treatment of slags. Even after the development of the coal fired reverberatory, or cupola, furnace at the end of the 17th century the ore hearth continued to be used in some mining fields, through to the close of the 19th century. It could be fired using a variety of fuels - dried chop wood and, in the Yorkshire Dales, peat - and, although coal has been found in 18th century and later contexts (associated with the use of the ore hearth for treating slags), it was not believed to have been in common use until the 19th century in the development known as the Scotch hearth. The use of mineral fuels is generally associated with the development of the reverberatory furnace and the shift to smelting on or close to the coalfields in the 18th century.
However, significant amounts of coal have been found in the residues from what is believed to be an ore hearth smelting operation, treating lead/silver ores, at Combe Martin, in North Devon, and dating from the late 16th century through to circa 1690.(10) The quantity of coal and the context in which it is found suggests that it was used to fuel lead/silver smelting, up to hundred years before its common use in lead smelting using the reverberatory furnace, and perhaps two hundred earlier than the previous evidence for its use in the ore hearth.(11) There are questions to be answered as to the source of the coal and the reasons for its use at Combe Martin. Was it the answer to a local fuel shortage or was it a cost effective alternative to local organic sources and, if so, how does it fit in to the overall trend in the processing of non-ferrous metal ores ?
Analysis of the coal recovered from the excavations at Combe Martin tells us that it is a semi-anthracite with from 8 to 10 % volatile content.(12) Such coals were mined in south-west Wales, close to the coast in Carmarthenshire west of Llanelli, and we have evidence from that area, in the portbooks, of shipments overseas in the late 16th / early 17th century and coastwise from the late 17th century, including shipments to the North Devon creeks.
There is a general acceptance amongst historians that one of the factors stimulating the industrial revolution of the late 18th century/early 19th century in Britain was the shift to mineral sources of fuel, and the use of that fuel to generate power; releasing human and agricultural resources to industrial purposes.(13) The move away from organic fuel for domestic purposes was well underway in Britain by the end of the medieval period, and coal had certain industrial uses throughout, but presence of coal at Combe Martin suggests that change was taking place in non-ferrous metallurgy perhaps one hundred years earlier that previously thought. The factors affecting this change require further investigation.
We should, however, not be surprised that the Combe Martin mines should be the first to use coal for lead/silver smelting given their proximity to a coastal coalfield and the ease with which coal could be shipped from South Wales.