Slant

A roadway or working driven at a steep angle into a coal seam, used in Wales in place of a vertical shaft where the geology allowed it.

Historical usage

Where a coal seam's angle and depth suited it, South Wales collieries could be opened and worked entirely through a slant, avoiding the cost of sinking a vertical shaft altogether. Pentremawr Colliery, in the Gwendraeth valley, is a documented example: driven as a slant mine, it worked its anthracite through three initial slants — Capel Ifan Nos.1, 2 and 3 — with a fourth added in 1913, needing no shaft at all.

How it worked

A slant was driven at roughly 30 to 45 degrees from the surface (or from a level roadway) down into the seam, following its natural angle rather than cutting straight down through it; within a working district, similar angled roadways also connected gate roads to the main haulage, cutting down on how much level roadway had to be maintained.

Why it was used

Where the coal seam's own angle made it practical, a slant let a colliery reach its coal without the far greater capital cost, and time, of sinking and lining a vertical shaft.

Risks & limitations

Slant mines remained exposed to the same underground hazards as any colliery — at Pentremawr, geological faults and gas accumulation limited commercial extraction despite the mine's access advantages.

Regional variation

'Slant' is the Welsh term for this kind of angled roadway; equivalent workings elsewhere in Britain were known by other regional names, including 'downbrow' in some coalfields and 'gug' in Somerset.

Sources

1. (secondary) Glossary of coal mining terminology — Wikipedia
2. (secondary) Pentremawr Colliery — Wikipedia

Record created: 27 August 2026 · Last researched: 27 August 2026