Tophole System

A local variant of the pillar-and-stall method used in the steep seams of the western South Wales Coalfield, in which levels driven along the seam had narrow rises -- 'topholes' -- driven off them to the full pitch of the seam at regular intervals, the coal sliding down them by gravity to be loaded into trams in the level below.

Historical usage

Named and described in these exact terms by H.M. Inspector of Mines in the official report into the 1929 Wernbwll Colliery explosion, which called it 'a modification of pillar and stall, locally known as the "Tophole" system, ... common to most of the mines working steep seams in the Western area of the South Wales coalfield.' The Northern Mine Research Society's own account of the same disaster independently describes the same layout in near-identical technical terms and dimensions.

How it worked

Levels, typically 9 feet wide, were driven off a slant on the full dip of the seam, spaced 40 to 60 yards apart. Topholes, also 9 feet wide and spaced about 14 yards apart, were driven from each level to the full rise, with narrower crossings, about 7 feet wide, cut between adjacent topholes for ventilation. Coal won by hand and shotfiring at the tophole faces and in the crossings was cast onto iron sheets laid in the topholes, down which it slid under gravity to the level below, where trammers loaded it into trams for haulage to the slant.

Why it was used

Suited to seams too steep for horizontal roadways to be worked conventionally; letting gravity carry the coal down the topholes to the level avoided the cost and difficulty of mechanical haulage on a steep pitch.

Risks & limitations

The narrow, steeply pitched topholes and crossings gave firedamp and coal dust little room to disperse, and were hard to stone-dust or ventilate thoroughly. The official inquiry into the 1929 Wernbwll explosion, which killed seven men in the No.13 level's topholes, found the district had never been stone-dusted and concluded that untreated coal dust in the topholes had spread what began as a small pocket of gas ignited at an open lamp flame far beyond what the initial ignition alone would have caused.

Regional variation

Recorded specifically for the steep seams of the western South Wales Coalfield; the general method it modifies, pillar and stall, and its other regional names (Bord and Pillar, Stoop and Room), are covered on the Room and Pillar term page.

Related terminology

Room and Pillar

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.

• Wernbwll Colliery — Swansea (well documented example)
  The colliery's own working method, precisely dimensioned in the mine's workings field; automated sweep missed it due to a quote mark interrupting the exact phrase.

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.

• Wernbwll Colliery explosion, 1929 (contributing factor)
  The official inquiry blamed untreated coal dust in the topholes for spreading the explosion beyond its initial small ignition.

Sources

1. (primary) Wernbwll Colliery Disaster Report (H.M. Inspector of Mines) — Durham Mining Museum (official inquiry report)
2. (secondary) Wernbwll Colliery Explosion - Penclawdd - 1929 — Northern Mine Research Society

Record created: 14 September 2026 · Last researched: 14 September 2026