Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
          <chap>
            <p type="caption">
              <s>
                <pb pagenum="144"/>
              similarly straight and at such an angle, that with its upper end it may reach
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              the upper end of the second cord, and with its lower end the last end of the
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              first cord. </s>
              <s>The length of the third cord shows the depth of the shaft, as I
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              said before, and at the same time that point on the tunnel to which the shaft
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              will reach when it has been sunk.</s>
            </p>
            <p type="main">
              <s>If one or more shafts reach the tunnel through intermediate drifts and
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              shafts, the surveyor, starting from the nearest which is open to the air,
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              measures in a shorter time the depth of the shaft which requires to be sunk,
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              than if he starts from the mouth of the tunnel. </s>
              <s>First of all he measures
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              that space on the surface which lies between the shaft which has been sunk
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              and the one which requires to be sunk. </s>
              <s>Then he measures the incline of all
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              the shafts which it is necessary to measure, and the length of all the drifts
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              with which they are in any way connected to the tunnel. </s>
              <s>Lastly, he
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              measures part of the tunnel; and when all this is properly done, he demon­
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              strates the depth of the shaft and the point in the tunnel to which the shaft
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              will reach. </s>
              <s>But sometimes a very deep straight shaft requires to be sunk
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              at the same place where there is a previous inclined shaft, and to the same
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              depth, in order that loads may be raised and drawn straight up by machines.
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              </s>
              <s>Those machines on the surface are turned by horses; those inside the earth,
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              by the same means, and also by water-power. </s>
              <s>And so, if it becomes
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              necessary to sink such a shaft, the surveyor first of all fixes an iron screw
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              in the upper part of the old shaft, and from the screw he lets down a cord
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              as far as the first angle, where again he fixes a screw, and again lets down the
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              cord as far as the second angle; this he repeats again and again until the
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              cord reaches to the bottom of the shaft. </s>
              <s>Then to each angle of the cord he
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              applies a hemicycle, and marks the waxed semi-circle according to the lines
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              which the tongue indicates, and designates it by a number, in case it should be
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              moved; then he measures the separate parts of the cord with another cord
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              made of linden bark. </s>
              <s>Afterward, when he has come back out of the shaft,
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              he goes away and transfers the markings from the waxed semi-circle of the
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              hemicycle to an orbis similarly waxed. </s>
              <s>Lastly, the cords are stretched on the
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              surveyor's field, and he measures the angles, as the system of measuring by
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              triangles requires, and ascertains which part of the footwall and which
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              part of the hangingwall rock must be cut away in order that the shaft may
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              descend straight. </s>
              <s>But if the surveyor is required to show the owners of the
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              mine, the spot in a drift or a tunnel in which a shaft needs to be raised
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              from the bottom upward, that it should cut through more quickly, he
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              begins measuring from the bottom of the drift or tunnel, at a point
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              beyond the spot at which the bottom of the shaft will arrive, when it has been
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              sunk. </s>
              <s>When he has measured the part of the drift or tunnel up to the first
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              shaft which connects with an upper drift, he measures the incline of this
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              shaft by applying a hemicycle or orbis to the cord. </s>
              <s>Then in a like manner
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              he measures the upper drift and the incline shaft which is sunk therein
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              toward which a raise is being dug, then again all the cords are stretched in
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              the surveyor's field, the last cord in such a way that it reaches the first, and
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              then he measures them. </s>
              <s>From this measurement is known in what part </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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