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Pit Workers in the Old Days #4: "Kayarimono (Dangerous Rock Bed Roofs)"
1958 - 1963

Mukashi no Yamabito #4: "Kayarimono (Tenjo no Bota)"
[Pit Workers in the Old Days #4: "Kayarimono (Dangerous Rock Bed Roofs)"]
21.1 x 30.3 cm Ink Painting

The rock bed roof called a "kayarimono" usually fell when mining coal. However, it did not fall together with the coal. These rock beds were so dangerous that they suddenly fell even if they did not seem to be crumbling. Hewers would not support them with pillars because such pillars disturbed them in their work, and miners were sometimes hit by falling roof rocks.
Some pits had roofs of white rocks, and others had black ones, and they were different in thickness. The kayarimono was also called a koten at some pits. Each hewer cut the middle of his coalface first before cutting off the top and bottom parts of it. They did not use dynamite.
The rock bed on the kayarimono consisted of never-falling colloidal basaltic shale. Therefore, the bottom rock was also hard. The above dangerous rock beds were seen above the thin series of coal and rock layers called a sanjaku-so at K Coal Pit and S Coal Pit run by Mr. A.

Text at the Bottom Left
A rock layer with the thickness of about 30 mils (0.76 mm) lay about 1.5 centimeters above the bottom rock and was called a sonoshita-rokusun.

Translation Assisted by Mr. Nathan Johndro

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