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"Beamworks" was the name given by the tinners to workings where the lode was followed by digging down from the surface, and the massive gullies that resulted remain prominent features of Dartmoor today. Several of these gullies retain names that include the word beam: Gibby Beam, Willabeam and Scudley Beam, for example. They are also known as "openworks" or "gerts".
Another method of surface mining involved digging pits at intervals along the lode this was known as "lodeback-work". At times these pits were dug in pairs along the back of the lode and the lode followed underground between them. This may have been the precursor to beamworks in a number of locations, but enough lodeback pits survive to indicate that it was a separate technique. The issue that mine managers had to decide was whether it was worth removing the extra overburden to form a gulley in order to be able to mine deeper into the lode.
In a similar fashion to streamworking, much use was made of water for the removal of the overburden and gangue. When digging large gullies the overburden, which consisted at least partly of decomposed granite ("growan"), was loosened with picks, and then water was used to wash away the unwanted material instead of manhandling it. Means of collecting, diverting and storing water were always associated with openworks. In some cases when only poor sources of water were available complex systems of reservoirs were built.
The Dartmoor tin industry declined in importance during the early 18th century and had fallen to nothing by 1730. This was due to a number of factors, but the most important was likely to be the exhaustion of the easily-accessible deposits. It was not until the Industrial Revolution fuelled demand for all metals and also provided the technology to mine them that mining resumed on the moor on any scale.
Although underground mining technology had been available for many centuries, it is likely that the joint problems of the hardness of the granite rock and the preponderance of underground water together with the relatively easy pickings from near the surface made deep mining not viable until the late 18th century.
Many small mining enterprises started up on Dartmoor in the late 18th and 19th centuries 48 mines are known to have produced some tin during this period. Many of these ventures were unsuccessful, despite being given optimistic names like Wheal Fortune, Wheal Lucky and Wheal Prosper (the common prefix Wheal is a Celtic word meaning mine or works). Some larger mines, however, such as Eylesbarrow and the Vitifer Birch Tor complex were productive for many years.
Virtually all of the underground mines re-worked lodes that had been already been mined from the surface. Because of the great quantity of underground water, it was necessary to dig horizontal adits into the hillsides to de-water the mines. Dartmoor's topography, cut with deep valleys, helped here and in many cases it was possible to dig to a reasonable depth without the need to pump out water. These adits connected with shafts that were either sunk vertically downwards or followed the line of the steeply dipping lode. Working the lode then took place by stoping from the horizontal levels in the usual manner.
When it became necessary to go deeper than the lowest adit, it was essential to pump out the water. Large waterwheels were used for this and where the shaft was higher than a good water supply, the waterwheel was located lower down the hillside and the power transferred up to the shaft by a "flatrod" system. Evidence for these systems survive as double rows of stones with grooves on their tops these held the pulleys that guided the metal rods. Such stone rows are still visible at Eylesbarrow and at Hexworthy.
The discovery of extensive tin deposits in Malaya in the later 19th century had a major impact on the Dartmoor industry, and many miners emigrated. The last tin mine on Dartmoor finally closed just before the Second World War.
After collection the tin ore had to be crushed, concentrated and then smelted. Over time a series of ever more sophisticated processes were used for these operations.