Underground Mining - Tin and Copper - Devon and Cornwall

Tin mining between the Tamar and Tavy had probably started by the 1180s, when tin working between Dartmoor and the Tamar was first mentioned. It seems largely to have come to an end in the later 18th century, probably due to the area's unusual mineralogy with tin being found above the copper, rather than below as was usual elsewhere in the region where the two minerals were found together.

Tin was worked outside this area until the early 20th century, Anderton Mine just east of Tavistock being in operation until the 1890s, with Drakewalls and Gunnislake Clitters in Cornwall working until 1910 and 1918 respectively.

The earliest documentary references to Copper working date from the early 18th century, when several leases were granted by the Bedford Estates. These survive in the Devon Record Office and are being studied by Robert Waterhouse and Fiona O'Connor. They are interesting as they positively identify a number of archaic looking workings in the Tamar and Tavy valleys. These share the common feature of being worked by gunnises from surface, with little or no evidence for shafts or adits. Of course, as most of the lodes also contained tin, it is difficult to date these gunnises, which could be much earlier. Particularly good examples of these include this steeply sloping crag working at Morwell Hatch Copper Work, and this vertical gunnis, one of a pair at Impham Mine (see Surface Workings page for details).

The oldest and perhaps the largest of these works was the Marquis, discovered in 1707 on the Devon bank of the Tamar just above Gunnislake, and described in some detail by Henric Kalmeter, who visited it in 1724 when it was being worked by the Bristol Copper Company. The mine was worked on two levels, formerly worked by separate companies. Both of these levels survive as tall gunnises, opening onto the river cliff above the Tamar. The lower of the two is the earliest, formerly called the Bedford Work. This later became the deep adit for the united mines, which became known as the Marquis Work.

The Marquis shared with George & Charlotte Mine the rare distinction in the Tamar Valley of having an underground waterwheel for pumping. This is described in the Water Power webpage.

It should not be assumed that all these mines used gunnises alone as an extraction method. In theory, gunnises were worked from above, with all the ore and waste rock having to be hauled to surface. On the steep valley sides, these gunnises could be worked sideways instead, the spoil and ore being carried out on the level, or at least up shallow slopes.

When mines began to be developed deeper, the old methods were found to be unsuitable and new techniques were required. Thus the use of shafts for access and haulage, and adits for extraction and drainage, began, with stopes being unencumbered by ladderways and barrow-ways. The early 18th century copper workings are interesting as they show both techniques, often existing alongside each other.

Many other such workings are thought to have existed, but have been lost due to the practice of using abandoned workings as dumps for later waste. George & Charlotte Mine's gunnises, up to 300m in length, have been lost in this way, probably when Cross-Course Shaft was sunk in the 1840s.

Shaft and adit mining principally for copper, seems to have commenced by the mid-18th century. As elsewhere in Britain, it had been found that the old methods of small-scale digging in relatively small mines were not economic when greater depths were reached. A different approach to drainage was also needed, as a result of the introduction of water power. Vertical shafts were necessary to accommodate the pumping rods, making it necessary to create practical means, in the form of larger horizontal levels opening out on the valley sides, for the miners to take the mined ore out in larger quantities.

The dimensions of the shafts and levels were often small in these later 18th to early 19th century workings. The introduction of mechanical methods of ore removal meant that the older, narrower levels had to be widened to accommodate, initially, wheelbarrows; then by the mid-19th century, railway waggons.

Wheelbarrows were apparently not introduced until the early 19th century and coffin levels which have been converted for barrow use are common in the district. This section of the George & Charlotte Mine's middle adit shows the narrow handpicked coffin level 1, enlarged for wheelbarrows by breaking out the footwall 2. Levels used by barrows often retain a longitudinal running plank, supported on transverse sleepers. This survived well in Middle Adit, also having evidence for packing pieces held in place by wedges to hold the board central. This probably got around the problem of iron nails, which could not be used in these sulphide mines for long, due to the acidic water.

19th century mining in the district is characterised by the universal use of shaft and adit mining, giving vertical and horizontal access to mineral lodes which were stoped to remove the minerals. Where gunnises survived from earlier workings, these were filled in if abandoned, or sollared over in timber and waste rock piled on top; as at Lockeridge Mine near Bere Alston where stone arching was constructed over a gunnis as early as the 17th century and at Wheal Fanny, Devon Great Consols, where massive timber sollaring is still visible at the top of the great stope.

As much as possible, waste rock (known as 'deads') was dumped underground, on timber platforms in the worked-out stopes. This was especially important on mine sites on the steeply sloping valley sides, where surface dumping space was at a premium. Occasionally, serious landslides resulted from excessive dumping, such as that in 1856 when George & Charlotte Mine's main dump slid into the Tamar, blocking the navigable channel for three weeks (Plymouth & Devonport Journal).

This new form of mining relied heavily on water power (see Water Power pages). This produced large quantities of dedicated associated structures, some built of mortared killas, which in addition to the leat systems and wheel pits, could include long straight trenches, carrying flatrods across undulating ground from the water wheel to the pumping shaft; stone flatrod towers which carried the rods across deep valleys or roads; and balance bob pits to contain the see-saw mechanism which counterbalanced the pump rods in the shaft.

The development of 19th century metal mines was characterised by extensive buildings for various purposes, interconnecting roads and sometimes internal railway systems. Building complexes often clustered around shaft heads, main haulage adit portals, dressing floors and transhipment facilities alongside roads, railways and canal/river frontages. The buildings typically included powder magazines, offices, smithies, ore-breaking sheds and captain's houses. Although some houses are still occupied, some more remote sites survive as ruins, as can be seen here at Wheal Russell. Stone-built structures associated with water or steam power are covered in detail in the Water Power and Steam Power pages. Mine buildings and other built structures often survive relatively well in the dense woodland of the Tamar Valley, as can be seen in the accompanying photographs.

Often, mining historians and other observers fail to understand the interrelationship between surface structures and underground ones. The two are of course inextricably linked, but few researchers habitually study both. I have tried in these pages to put this right, by showing how the two can and must be studied together, if a mine site is to be fully understood. Of the handful of industrial archaeologists known to me, one absolutely refuses to go underground, citing safety reasons (principally Radon gas), while others are so wrapped up with the minutiae of surface surveys that they entirely fail to compare it with accessible subterranean archaeology or even much of its documented history.

It is a salient fact that of the five significant pieces of published research carried out by modern researchers into the mining history and archaeology of the Tamar Valley, not one has studied the underground resource, while surface remains are often covered in fine detail.

There really is no excuse for this - it is usually possible to get access to mine workings in a safe and organised way, simply by joining a reputable cave/mine exploration club. I started going underground with such a group ten years ago, with a long tradition of surveying accessible underground structures. This enabled me to understand how the underground workings of mines were exploited, with like-minded people with whom one could discuss the subject intelligently.

The Links page has details of the Plymouth Caving Group, which regularly visits Tamar Valley mines, while many other such groups exist elsewhere in Britain. (For more details see NAMHO)