Cymmer Colliery explosion, 1857

Ten months after the Cymmer explosion of 1856, two brothers, John and Thomas Jones, were suffocated by afterdamp after firedamp fired in an exploring drift at the Insoles' Cymmer Colliery, Porth, on a Monday morning in May 1857. The fireman had put up the danger signal and warned the men not to go in.

Cause

Firedamp in an exploring drift, which the fireman had marked as dangerous that morning; the brothers went in despite the warning and were overcome by the afterdamp.

What happened

That morning the fireman made his usual inspection, put up the signal of danger and warned the men not to enter the workings on any account. John and Thomas Jones went in all the same, into an exploring drift whose dangerous state they had been cautioned about. Firedamp exploded and both were suffocated by the choke or afterdamp. John left a widow and three children; Thomas had been married only a few months.

What's uncertain

Points where sources disagree or the record could not be settled; both accounts are kept. All open questions in the archive.

• The lists of deaths give the date as 12 May 1857; the newspaper's 'Monday week' points to 11 May. (disputed) ^1,2,3

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• On a Monday morning in May 1857 two brothers, John and Thomas Jones, were suffocated by afterdamp after an explosion of firedamp at the Insoles' Cymmer Colliery, Porth. ^1,2,3
• The fireman had been in that morning, had put up the danger signal and had warned the men not to enter on any account. ^1,3
• The brothers died going into an exploring drift after being cautioned about its dangerous state. ²
• The lists of deaths give the date as 12 May 1857; the newspaper's 'Monday week' points to 11 May. (disputed) ^1,2,3

Related terminology

Mining terms this disaster is structurally linked to, with the nature of the relationship.

• Afterdamp (contextual relationship)
  Named 3 times in this record, first in the summary: “…of 1856, two brothers, John and Thomas Jones, were suffocated by afterdamp after firedamp fired in an exploring drift at the Insoles' Cymmer…”
• Colliery (contextual relationship)
  Named in this record’s summary: “…after firedamp fired in an exploring drift at the Insoles' Cymmer Colliery, Porth, on a Monday morning in May 1857. The fireman had put up the…”
• Drift (contextual relationship)
  Named 3 times in this record, first in the summary: “…were suffocated by afterdamp after firedamp fired in an exploring drift at the Insoles' Cymmer Colliery, Porth, on a Monday morning in May…”
• Firedamp (contextual relationship)
  Named 3 times in this record, first in the summary: “…brothers, John and Thomas Jones, were suffocated by afterdamp after firedamp fired in an exploring drift at the Insoles' Cymmer Colliery, Porth,…”
• Fireman (contextual relationship)
  Named 3 times in this record, first in the summary: “…Cymmer Colliery, Porth, on a Monday morning in May 1857. The fireman had put up the danger signal and warned the men not to go in.”

Sources

1. (secondary) Welsh Coal Mines: fatalities 1857 — Welsh Coal Mines
2. (secondary) Ian Winstanley, alphabetical list of mining victims 1850-1859: I — Healey Hero (Ian Winstanley collection)
3. (primary) Pontypridd: another fatal colliery explosion, Cardiff and Merthyr Guardian, 23 May 1857 — Welsh Newspapers Online (National Library of Wales)

Record created: 23 October 2026 · Last researched: 23 October 2026