South Staffordshire Coal Field, England. Holers at work in a thick seam of coal, worked in a pillar and stall system, leaving pillars of coal to support the roof. The scene depicted is lit by a candle stuck in a wooden stand, a dangerous practice in coal mines where there is always a danger of the presence of the inflammable gas, methane (fire-damp). The invention of the miner's safety lamp in 12815 or 1816 made mine explosions less frequent. From The Popular Encyclopaedia, London, 1888.