The works of Sakubei Yamamoto
Monochrome

Dynamite and Undercutting
1958 - 1963

Dainamaito to Nakasukashi
[Dynamite and Undercutting]
21.2 x 29.9 cm Ink Painting

Text at the Right End and the Top
Miners paid their own expenses for dynamite until the end of World War II. Explosives with names, such as Sakura, Kobai, and so on, were extremely gelatinous. Two small pieces of dynamite 6 bu (about 1.8 cm) in diameter, a detonator, and a 2 shaku 5 sun (about 75 cm) long train cost 18 sen (0.18 yen) in total. Miners normally got paid 1 yen 5 sen (1.05 yen) per mine car of mined coal or about 1 yen 20 sen (1.2 yen) when they mined from difficult coalfaces (around 1941 or 1942).
Therefore, each miner did not use a lot of dynamite if possible. Sakiyamas (hewers) went into the pit around 3:00 a.m. to undercut their coalfaces as deep as possible. However, they pressed their underground bosses for day-laborers to help them in blasting even when they came across very small masses of hard silicified wood.
(A pair of miners [hitosaki: a hewer and a helper] who mined six mine cars of coal or more a day received an incentive of 18 sen per mine car. They also received an 8-yen bonus for diligence when they worked 23 shifts or more a month.)
The above problem disappeared when the expenses for blasting came to be paid by mine companies after the war. Miners came to use a lot of dynamite underground, but that was a matter of small importance because mining efficiency went up by about 80 % compared to before the war.
A series of coal and rock layers called a goshaku-so (five-shaku-thick layers: 150-centimeter-thick layers) was actually more than six shaku (180 cm) thick, and had a thick hard chamotte rock layer next to its thin top coal layer. There was a thin and soft rock layer lying at the height of six shaku or less. These layers were inclined about 12 or 13 degrees, and their inclination became uneven near faults.
There was another series of coal and rock layers called a sanjaku-so (three-shaku-thick layers: 90-centimeter-thick layers) 27 meters above the goshaku-so.

Text in the Box at the Bottom Right
Since a hitosaki used only four or five pieces of dynamite at one time, the chamotte layer was not shattered into small pieces. So, miners built fine stone walls along haulage ways with the big masses of broken chamotte. Building such walls was a real feat that only expert sakiyamas could do.

Descriptions of the Coal Layers at the Left End
[Top] Layer of Coking Coal with Caloric Value Greater than 7,000 kcal/kg (approximately 29,300 J/kg) Called Hassun
[Second] Rock Layer Called "Chamotte"
[Third] White Rock Layer Called a Nakasukashi Approximately 15 Millimeter Thick
[Bottom] The coal at the bottom layer had a caloric value greater than 6,000 kcal/kg (approximately 25,100 J/kg) and a few very thin rock seams lay within this layer.

Text at the Bottom Left
Right-handed hewers were not called experts before they became able to use their pickaxes as well as left-handed ones.


Translation Assisted by Mr. Nathan Johndro

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