（解説文要約）
炭車の配送係を「ノリマワシ」または「サオドリ」と言います。
坑内を網の目のように走る線路に、効率よく炭車を配送しなくてはいけません。
どこかで詰まってしまうと、採炭現場で炭車待ちが発生してしまうからです。
この作品には、作兵衛翁がいた炭坑で「サオドリ」が精鋭の担当者に代わったら、
生産能率が大幅に上がったという話が記されています。
The two men depicted here were called "Nori-mawashi" or "Saodori".
These coal car operators had to efficiently send empty coal cars to the railway network underground.
If even one rail got stuck, miners had to wait for the arrival of empty coal cars, hindering their work at the coal faces.
In the text, Sakubei tells about his colliery.
Once experienced Norimawashi or Saodori took charge of the coal car operations, output rates dramatically increased!