（解説文要約）
掘り出した大小のボタで採炭跡の空間を埋める様子を描いた作品です。
この作業は賃金が高くつくので、小さな炭坑では行われませんでした。
大きなボタで四角く囲いを作り、中に小さなボタを詰め込みます。
この方法をボタコヅミと言います。
下手な素人が作ると見せかけだけになってしまい、すぐに崩れて何の役にも立たなかったそうです。
This painting depicts a wall, called "Botakozumi", created of discarded rocks of various sizes sorted while mining.
Major mines made use of these waste rocks to strengthen the coal drives.
First, 2-meter-square walls were made by piling up large rocks, then they were filled in with smaller rocks.
Because the extra wages paid to workers to make these walls drove up costs, this labor-intensive method was not used in minor pits.
Since they collapsed easily, the walls constructed by inexperienced workers were of no use at all.