（解説文要約）
石炭層の高さが1.5メートルあれば立って掘ることができます。
掘り方としては、絵のように初めは中段を深く掘っていき、
次に下段と上段を掘ることが、最も効率的なやり方だったようです。
しかし、石炭層には硬いボタもあり、また、イタメやマサメもあり、
とても苦労して採炭していたようです。
Miners were able to dig for coal in a standing position when the coal bed was as wide as 1.5 meters.
The most efficient way was, as seen in the painting, to first cut deep into the middle of the bed,
then to dig the lower and upper sections of this hole.
Some mines were not as easy to dig as others. Some consisted of hard rocks.
And there were various types of seams such as Itameor Masame, differing in the direction of the fissure layers.
Hewers used a wide range of techniques to extract the coal which was incredibly hard labor.