Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
          <chap>
            <p type="main">
              <s>
                <pb pagenum="119"/>
              out because of the hardness or other difficulty, and the drift or tunnel is
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              low, a heap of dried logs is placed against the rock and fired; if the drift or
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              tunnel is high, two heaps are necessary, of which one is placed above the
                <lb/>
              other, and both burn until the fire has consumed them. </s>
              <s>This force does not
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              generally soften a large portion of the vein, but only some of the surface.
                <lb/>
              </s>
              <s>When the rock in the hanging or footwall can be worked by the iron tools
                <lb/>
              and the vein is so hard that it is not tractable to the same tools, then the
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              walls are hollowed out; if this be in the end of the drift or tunnel or above
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              or below, the vein is then broken by fire, but not by the same method; for
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              if the hollow is wide, as many logs are piled into it as possible, but if narrow,
                <lb/>
              only a few. </s>
              <s>By the one method the greater fire separates the vein more
                <lb/>
              completely from the footwall or sometimes from the hangingwall, and by the
                <lb/>
              other, the smaller fire breaks away less of the vein from the rock, because in
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              that case the fire is confined and kept in check by portions of the rock which
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              surround the wood held in such a narrow excavation. </s>
              <s>Further, if the
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              excavation is low, only one pile of logs is placed in it, if high, there are
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              two, one placed above the other, by which plan the lower bundle being
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              kindled sets alight the upper one; and the fire being driven by the draught
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              into the vein, separates it from the rock which, however hard it may be, often
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              becomes so softened as to be the most easily breakable of all. </s>
              <s>Applying this
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              principle, Hannibal, the Carthaginian General, imitating the Spanish miners, </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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