（解説文要約）
古くなった坑木は、家庭の燃料として使っていました。
ほとんどの坑木は松の木で、火力がなく煙を多く出します。
しかも、杉のようには割れにくく、薪割り(まきわり)にも上手い下手の差が出ていたようです。
Old mine timbers were used as a fuel for domestic use.
Most mine timbers were pine wood and they emitted weak heat and much smoke when burnt.
Moreover, they were not as easy to chop as cedar wood and it seemingly depended on the skill of the person who chopped them if they were nicely chopped.