Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
          <chap>
            <p type="caption">
              <s>
                <pb pagenum="124"/>
              are arranged on two different systems; for either the square ends of the
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              timbers, which reach from the hangingwall to the footwall, are fixed into corres­
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              ponding square holes in the timbers which lie along the hanging or footwall,
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              or the upper part of the end of one and the lower part of the end of the other
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              are cut out and one laid on the other. </s>
              <s>The great weight of these joined
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              timbers is sustained by stout beams placed at intervals, which are deeply set
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              into hitches in the footwall and hangingwall, but are inclined. </s>
              <s>In order that
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              these joined timbers may remain stationary, wooden wedges or poles cut
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              from trees are driven in between the timbers and the vein and the hanging
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              wall and the footwall; and the space which remains empty is filled with loose
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              dirt. </s>
              <s>If the hanging and footwall rock is sometimes hard and sometimes soft,
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              and the vein likewise, solid joined timbers are not used, but timbers are
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              placed at intervals; and where the rock is soft and the vein crumbling,
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              carpenters put in lagging between them and the wall rocks, and behind these
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              they fill with loose dirt; by this means they fill up the void.</s>
            </p>
            <p type="main">
              <s>When a very deep shaft, whether vertical or inclined, is supported by
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              joined timbers, then, since they are sometimes of bad material and a fall is
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              threatened, for the sake of greater firmness three or four pairs of strong end
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              posts are placed between these, one pair on the hangingwall side, the other
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              on the footwall side. </s>
              <s>To prevent them from falling out of position and to
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              make them firm and substantial, they are supported by frequent end plates,
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              and in order that these may be more securely fixed they are mortised into
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              the posts. </s>
              <s>Further, in whatever way the shaft may be timbered, dividers
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              are placed upon the wall plates, and to these is fixed lagging, and this
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              marks off and separates the ladder-way from the remaining part of the shaft.
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              </s>
              <s>If a vertical shaft is a very deep one, planks are laid upon the timbers by the
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              side of the ladders and fixed on to the timbers, in order that the men who are
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              going up or down may sit or stand upon them and rest when they are tired.
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              </s>
              <s>To prevent danger to the shovellers from rocks which, after being drawn up
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              from so deep a shaft fall down again, a little above the bottom of the shaft
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              small rough sticks are placed close together on the timbers, in such a way as
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              to cover the whole space of the shaft except the ladder-way. </s>
              <s>A hole,
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              however, is left in this structure near the footwall, which is kept open so that
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              there may be one opening to the shaft from the bottom, that the buckets
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              full of the materials which have been dug out may be drawn from the
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              shaft through it by machines, and may be returned to the same place again
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              empty; and so the shovellers and other workmen, as it were hiding beneath
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              this structure, remain perfectly safe in the shaft.</s>
            </p>
            <p type="main">
              <s>In mines on one vein there are driven one, two, or sometimes three
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              or more tunnels, always one above the other. </s>
              <s>If the vein is solid and
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              hard, and likewise the hanging and footwall rock, no part of the tunnel
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              needs support, beyond that which is required at the mouth, because at that
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              spot there is not yet solid rock; if the vein is soft, and the hanging and
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              footwall rock are likewise soft, the tunnel requires frequent strong timbering,
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              which is provided in the following way. </s>
              <s>First, two dressed posts are erected
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              and set into the tunnel floor, which is dug out a little; these are of medium </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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