Adit

A level tunnel, usually driven into a hillside or valley side, giving access to a mine and used for drainage or for hauling out broken ore, without the cost of raising everything up a shaft.

Historical usage

Adits were in use in Cornwall before 1500, and became essential to the tin and copper industry because the county's ore-bearing lodes run near-vertically, acting as channels for groundwater to flood into workings. As mines deepened through the 18th and 19th centuries, adits were extended for miles between setts to reach a valley low enough for water to drain away by gravity.

How it worked

Water drains out through the tunnel's slight upward slope by gravity alone, so it only has to be raised mechanically as far as the adit rather than all the way to the surface. The deepest open adit on a mine is its 'drainage adit' and sets the depth to which the mine can be unwatered without pumping. Not every adit reaches the surface: deeper ones sometimes ran from distant workings back to a pumping shaft rather than daylight, carrying water to where it could be lifted mechanically the rest of the way.

Why it was used

An adit is far cheaper to run than pumping, since it moves water using gravity rather than engine power, and it gives a second means of access and ventilation besides the shaft. Where the topography allowed a tunnel to be driven into a hillside below the workings, it was usually the first drainage measure tried, with pumping engines only added once mining went deeper than the adit could reach.

Risks & limitations

An adit can only drain a mine down to its own level — anything worked below that still needed pumping, which is why deep Cornish mines combined adits with beam engines rather than relying on adits alone. Adits also need suitable terrain: on flat ground, or where the lode lies far from a hillside, driving one is impractical or prohibitively long.

Regional variation

'Adit' is the term used in Cornwall and Devon; in the Derbyshire lead orefield the near-equivalent drainage tunnel is called a sough — the same drainage principle under a different regional name. The broader term 'level' refers to any horizontal working driven from a shaft rather than the surface, and 'drift' to a horizontal passage that need not reach the surface at all — an adit is specifically the kind that does.

Images

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Ecton Copper Mines — Staffordshire (well documented example)
  The Whey Adit is a well-documented, walkable example, later reused to store whey for a nearby creamery.
• Bradda Head Mines — Isle of Man (historical documentary reference)
  South Bradda's adit, driven from halfway up the cliff face, is a documented part of the mine's recorded workings.

Disasters associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis, with the nature of the relationship stated — not every disaster where this term might plausibly apply.

• Wheal Jane acid mine water discharge, 1992 (relevant method/equipment)
  The 1992 discharge escaped through the Nangiles adit, a well-documented case of an adit acting as the drainage route for a pollution incident.

Sources

1. (secondary) A Cornish mining glossary — Cornish Mining World Heritage Site (UNESCO)
2. (secondary) Adit — Wikipedia

Record created: 20 August 2026 · Last researched: 20 August 2026