In a primitive mine the ventilation was driven by convection (believe it or not, they sometimes lit bonfires down mines - yes, methane gas, explosion risk and all - to create an upward airflow in one shaft and draw in fresh air via another opening). For this to work it was essential to keep certain passages open and others shut in order to direct the flow of air where it was needed.
If a tub (cart for carrying coal) needed to pass through a closed trap, the trapper held it briefly open,, then shut it as soon as possible behind the tub. This work was often done by miners' children too young to win coal, to load or to push tubs.
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Opened and shut trap-doors.
In a primitive mine the ventilation was driven by convection (believe it or not, they sometimes lit bonfires down mines - yes, methane gas, explosion risk and all - to create an upward airflow in one shaft and draw in fresh air via another opening). For this to work it was essential to keep certain passages open and others shut in order to direct the flow of air where it was needed.
If a tub (cart for carrying coal) needed to pass through a closed trap, the trapper held it briefly open,, then shut it as soon as possible behind the tub. This work was often done by miners' children too young to win coal, to load or to push tubs.
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