The industrial mining landscape and economy, from 1700 to 1914
 

The nomination of the Cornwall and West Devon Mining Landscape for inclusion on the World heritage List is for the most universally significant era of Cornish mining between 1700 and 1914.

 

From 1700 there are a number of general characteristics which distinguish this period of metalliferous mining in the nominated Site from any preceding period. They were:

  • the steady growth in Cornish and Devon tin production which was represented mostly by exploitation in depth and was based on underground lode mining (as opposed to tin streams). Small-scale tin-blowing was gradually replaced by larger-scale coal-fired reverberatory smelting.
     

  • landmark technical advances in steam pumping which marked the formative period of the Industrial Revolution in Cornish mining. By the end of the eighteenth century deep mining was made possible by the development of this new technology.
     

  • the mining of copper which experienced steady growth from the beginning of the eighteenth century. From 1750 to 1850 it was the most important mineral in the region. Cornish and West Devon output dominated the world’s copper markets.

East Pool Mine. 180-fathom level. J. C. Burrow, 1893. © Royal Cornwall Museum.

  • the laying down of the industrial transport infrastructure during the late eighteenth and early nineteenth centuries. This was essential to the production of copper. The major mining ancillary industries (such as engineering) were also established. the mining of a wide range of other metals (such as silver, lead, zinc, iron, manganese, tungsten, antimony and cobalt) between the late-eighteenth and the mid nineteenth century. These were as diverse as any mining field in the world. During the early nineteenth century Cornwall was the first centre of world arsenic production and during the later nineteenth century West Devon was its leader.
     

  • the availability of large-scale employment in the industry which caused major population growth, spawned new settlements and a range of institutions for self-improvement and scientific study. There was a corresponding growth in agriculture and a large-scale emergence of miners’ smallholdings. Great houses were built or remodelled and estates and gardens were created or expanded on profits from the  industry.
     

  • the export of Cornish mining technology and equipment during the nineteenth and early twentieth centuries and the global diaspora of the Cornish mining population.
     

  • 1914 is a significant date in the mature phase of the British Industrial Revolution. It marks the commencement of the First World War and a significant reduction in economic growth. One effect of the war was to dramatically increase the demand for tungsten (for armaments), which stimulated some mines and led to some new mines being started. However by 1919, in the midst of a post-war slump, the Cornish mining industry was changed radically and forever.

Tin

A substantial amount of tin output in the region came from tin-streaming. Until the eighteenth century most tin came from these deposits. From the eighteenth century lode mining became dominant. There was a virtual absence of world competition in tin mining until the 1820s and the market remained dominated by Cornish tin until the 1870s. Periods of increased demand, such as the rapid rise of the tin-plate industry after 1800, strongly influenced the metal market price and hence production levels. The ability to increase production however depended upon the available mining technology of the time. The introduction of gunpowder for blasting and of reverberatory furnaces for smelting began a rising trend in production towards the end of the seventeenth century. From 1700 there began a steady improvement in the understanding of the nature of tin mineralisation and hence the ability to predict where tin deposits might lie. The development towards an industrial economy, with the ability to raise risk capital from investors, was a crucial factor that enabled expansion of the industry.
 

Cornwall and Devon average decennial tin production. © HES.
 

The improvement of steam pumping technology during the second half of the eighteenth century, and dramatic improvements to the Cornish engine from the 1820s enabled deeper mining and greater output. Cornish tin mines survived the threat of competition during the 1820s and 1840s from producers in the Far East. Following the 1866 copper crash, and the closure of a large percentage of Cornish copper mines, tin mines became the principal mines in the nominated Site. The 1870s marks the peak production period at a time when Malayan production was temporarily halted by internal political anarchy. From 1874 production declined as Australia and Malaya produced a large output from extensive shallow deposits of cheaply exploited ore that continued to be mined through the 1880s and 90s. The consequent drop in the tin price, coupled with a decline in investment and the irony of a shortage of miners due to emigration, caused production to continue to fall sharply. It was not until the second half of the twentieth century that there was a substantial recovery in output. This followed a programme of financial support targeted at the mining industry by the United Kingdom.
 

Copper

In 1785 the exploitation of the large and shallow deposit of copper-rich sulphide ores at Parys Mountain on Anglesey (North Wales) precipitated a sharp economic downturn in the fortunes of many Cornish mines. During this period, British copper production exceeded demand by a large margin, whilst a struggle for the control of the copper market between the smelters and the Cornish producers resulted in a glut of copper on the world market; inevitably this was followed by numerous mine closures.

In the event, the readily-exploitable ores at Parys Mountain were worked out within two decades. Meanwhile the Cornish had responded to this threat to their mining economy through marked improvements in pumping technology and better working methods. During the early years of the nineteenth century Cornwall had once again become the pre-eminent copper ore producer in Britain, indeed, in the world; and was to remain so for several decades.
 

Cornwall and Devon average decennial copper production. © HES.
 

The Consolidated Mines in Gwennap produced 442,493 tons of copper ore between 1819-1858, and the adjacent United Mines 347,640 tons from 1815-1861; the area was so rich that it was dubbed ‘the Copper Kingdom’. In the 1830s Cornwall completely dominated world copper production. However, two decades later Chile's production far exceeded Cornwall's output and the Lake Superior mines (N. America) and those in South Australia were developing fast. Cornwall and Devon's peak year for production was 1855-6, when 209,305 tons of ore were mined. By the end of that decade tin was replacing copper as the region’s most important mineral, particularly in its western mines, and in 1866 a disastrous crash in the copper market occurred which Cornish copper mining could not survive. Chile, Australia, Lake Superior, Montana, and Arizona spelt the end for Cornish copper mines and for the Welsh smelters. Some Cornish mining districts were fortunate in that they also possessed tin reserves, and through increasing mechanisation and the adoption of efficient ore-dressing technology, their mines were able to work on towards the end of the century, despite falling tin prices. Some former copper mines found a new lease of life in working the arsenical pyrite which they had formerly discarded as waste. Devon Great Consols in the Tamar Valley produced nearly two-thirds of the world's arsenic during the closing years of the nineteenth century. Nevertheless, the great days of Cornish mining were over and, one by one, mines whose reputation had spread far beyond Cornwall were abandoned.

Arsenic

During the early nineteenth century Cornwall pioneered world arsenic production as a by-product of tin and copper mining in the western part of the nominated Site (Gwennap Mining District). The first commercial British arsenic was produced at Perran-ar-Worthal in 1812, followed by a works at Bissoe (1834) in the Carnon Valley that became a stronghold of arsenic production. Its principal market was the expanding Lancashire cotton industry which used it in pigments and dyes.

It was also used by other industries such as glass manufacture (as a decolouriser), in the production of lead-shot, in leather tanning, in wallpaper manufacture (to create green and yellow print), in pharmaceuticals, in agriculture for sheep dips and, from the 1870s, as a pesticide to control the Colorado beetle which devastated potato, tobacco and other crops in America during the late nineteenth century.

The principal arsenical insecticides were Paris green (from 1869) superseded by London purple (from 1878). During the latter half of the nineteenth century the leading world output came from the eastern part of the nominated Site (Tamar Valley). Production of this semi-metal prolonged prosperity long after other metalliferous productions had declined.

Calciners or ‘burning houses’ (furnaces) were an essential part of most eighteenth century Cornish tin mines whose ores contained arsenic and sulphur. These essential elements had to be ‘cleansed out’ by roasting as they proved deleterious to smelted tin. It was not until the nineteenth century however that demand arose, induced by technological advances, for the white arsenious oxide.

Bissoe sulphuric acid works, painted by Lamorna Birch (1869-1955). Later, in the nineteenth century the Carnon Valley was a centre of chemical production for sulphuric acid and other by-products from mine waste.

For some flagging copper mines, the working of arsenic provided several more years of profitable work and in some cases these ores became their principal output. Substantial works were established at the English Arsenic Company factory at Roseworthy, Gwithian and at Greenhill near Gunnislake, but the largest in the region was at Devon Great Consols, which at its peak produced 3,000 tons of refined arsenic a year. It was in the 1870s that a handful of mines in the Tamar Valley mining district were producing over half of the world’s arsenic; the works at Wheal Anna Maria (part of Devon Great Consols) covered 3.2 hectares and had over 6,850 cubic metres of arsenic flues.

 

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