Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
          <chap>
            <pb pagenum="56"/>
            <p type="main">
              <s>Others, on the contrary, run from north to south.</s>
            </p>
            <figure number="18"/>
            <p type="caption">
              <s>A, B, C—VEIN. D, E, F—
                <emph type="italics"/>
              Seams in the Rocks.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>The seams in the rocks indicate to us whether a vein runs from the
                <lb/>
              east or from the west. </s>
              <s>For instance, if the rock seams incline toward the
                <lb/>
              westward as they descend into the earth, the vein is said to run from east
                <lb/>
              to west; if they incline toward the east, the vein is said to run from west
                <lb/>
              to east; in a similar manner, we determine from the rock seams whether
                <lb/>
              the veins run north or south.</s>
            </p>
            <p type="main">
              <s>Now miners divide each quarter of the earth into six divisions; and by
                <lb/>
              this method they apportion the earth into twenty-four directions, which they
                <lb/>
              divide into two parts of twelve each. </s>
              <s>The instrument which indicates these
                <lb/>
              directions is thus constructed. </s>
              <s>First a circle is made; then at equal
                <lb/>
              intervals on one half portion of it right through to the other, twelve
                <lb/>
              straight lines called by the Greeks
                <foreign lang="grc">διάμετροι,</foreign>
              and in the Latin
                <emph type="italics"/>
              dímetíentes,
                <emph.end type="italics"/>
                <lb/>
              are drawn through a central point which the Greeks call
                <foreign lang="grc">κέντρον,</foreign>
              so that
                <lb/>
              the circle is thus divided into twenty-four divisions, all being of an equal
                <lb/>
              size. </s>
              <s>Then, within the circle are inscribed three other circles, the outer­
                <lb/>
              most of which has cross-lines dividing it into twenty-four equal parts; the
                <lb/>
              space between it and the next circle contains two sets of twelve numbers,
                <lb/>
              inscribed on the lines called “diameters”; while within the innermost circle
                <lb/>
              it is hollowed out to contain a magnetic needle
                <emph type="sup"/>
              3
                <emph.end type="sup"/>
              . </s>
              <s>The needle lies directly </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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