（解説文要約）
明治時代のまだ選炭機が導入されていない頃、
60度ぐらいの傾斜をつけて斜めに設置されたマンゴクという鉄の格子の上に石炭を放り込んでいました。
粉炭、つまり石炭の粉は鉄格子の下に落ち、塊炭（カイタン）だけが滑り落ちます。
さらに女性たちが、石炭とボタに選別します。
その後、石炭は、馬で鉄道貨車まで運ばれていました。
Around 1900, before the introduction of dressing machines in collieries, miners used iron lattice called Mangoku to sort out valuable coal.
They would dump out the extracted coal on the Mangoku positioned at a 60 degree angle
so that only the large chunks of coal would fall to the bottom and the powdered portions of the coal would fall through the slits.
There at the bottom, women would sort out the coal from stones and rocks.
After sorting the selected coal, chunks were sent to freight cars by horse drawn skips.