（解説文要約）
深い卸坑道では、掘削中にガスが出る恐れがあります。そのため、火花を出す電気は使いませんでした。
排水は蒸気ポンプで、オーガは圧搾空気で駆動します。
圧搾空気はエアーを吐き出すので換気にもなり、一挙両得でした。
卸坑道の最深部では、排水ポンプも水没の恐れがあるので、一旦箱に水をためてからポンプで排水していました。
Especially in the main drives of deep coal mines, the fear of gas was ever-present.
That's why electricity, which might cause sparks, wasn't used. To drain water, they used steam pumps.
To generate drills, they used compressed air, which also helped produce airflow in the pit.
At the bottom of these deep main drives, there was also a fear of underground water flooding the drainage pump.
To avoid such damage, once underground water was sucked up into a pool, it was drained outside with the pump.