Power - Water Power in Mining and Other Industries

The deep valleys of the Tamar and Tavy with their many tributaries made water power for industry easily available. Due to differing geographical conditions, the Cornish and Devon banks of the Tamar evolved in slightly different ways, but both relied heavily on leats or artificial water channels which brought water to the mines, which were often on high hillside locations.

There is little firm documentary evidence for this before c.1700, with one significant exception - the construction in the 1470s-80s of a ten mile long leat from the Lumburn Valley west of Tavistock to the Crown silver-lead mines near Bere Alston. This astonishing undertaking used several of the techniques described below, such as water augmentation, tunnelling and the crossing of watersheds. It is recorded as having driven underground waterwheels for pumping, probably in the vicinity of Lockridge Hill.

Wooden pump pipes are recorded as having been made at Plympton and brought up to the mine, presumably by barge. This woodcut (above right) shows wooden pump pipes illustrated in Georgius Agricola's mining treatise 'De Re Metallica' of 1556. (Claughton 1994, 57).

The rapid abandonment of this system suggests that such technology was alien to local miners and nothing similar seems to have been undertaken again for another 200 years. Wooden pipes containing plunger pumps were used in this case and one such pipe is known from a later but hitherto undated context in the Tamar Valley.

This pipe, probably of elm, bound with wrought iron bands to prevent it splitting, represents a rare survival of the pumping technology now known to have been available at the beginning of the 18th century. A similar, though again undated example, was found at Dolcoath Mine in Cornwall during the 1970s.

Although details of pumping wheels mounted at surface during this period are not known, one certain underground wheel and two possible ones are known from the Tamar Valley. The best-known was constructed between the higher and lower adits of the Marquis Copper Work, on the Devon bank of the Tamar just north of New Bridge, in 1724-25. This was described by the Swedish diarist Henric Kalmeter (See: Further Reading...) who saw it at the time of its construction, and fortunately for us, its chamber is still partly accessible. It was surveyed by the author in 2011 and the drawings will appear on this webpage when completed.

Three photographs of the lower part of the chamber are presented here and show how it was placed with its north end at right-angles to the deep adit, which carried pumped water and the wheel's tailrace out to the river. Only a 1.5 metre high portion of the chamber's wider upper part and 2.5 metres of its narrower lower half are now accessible - the approximately 5 metres of intervening height having been used in the 19th century to dump deads in.

An internal pumping and hauling shaft - Blount's Shaft - was sited at the south end of the chamber, but this is now choked with deads. A short section of the leat tunnel by which the water was brought to the wheel has survived and can be seen here. The peculiar cross-section has been caused by the leat tunnel (lower left) being cut out of one side of a pre-existing level (upper right). The leat channel is represented by the lower part of the floor to the left: the plank may be a remnant of a timber launder.

Access to the mine workings is controlled by the Plymouth Caving Group and they are managed as a winter bat roost, being closed between October and March.

It seems that water wheels were sited underground in the 18th century due to their relative inefficiency, meaning that placing the power source as close to the pumps as possible was desirable. Another factor was the availability of a reliable water supply, which was not possible above a certain height on the Devon bank of the Tamar until 1817, when the Tavistock Canal was opened.