Agricola, Georgius, De re metallica, 1912/1950

Table of figures

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            <p type="caption">
              <s>
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              cling to the coverings. </s>
              <s>Pockets are made in various ways, either with iron
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              wire or small cross-boards fixed to the frame, or by holes which are sunk
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              into the sluice itself or into its head, but which do not quite go through.
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              </s>
              <s>These holes are round or square, or are grooves running crosswise. </s>
              <s>The
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              frames are either covered with skins, pieces of cloth, or turf, which I will
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              deal with one by one in turn.</s>
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              <s>In order to prevent the sand which contains the particles of gold from
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              spilling out, the washer fixes side-boards to the edges of a plank which is six
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              feet long and one and a quarter wide. </s>
              <s>He then lays crosswise many iron
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              wires a digit apart, and where they join he fixes them to the bottom plank
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              with iron nails. </s>
              <s>Then he makes the head of the frame higher, and into this
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              he throws the sand which needs washing, and taking in his hands the handles
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              which are at the head of the frame, he draws it backward and forward
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              several times in the river or stream. </s>
              <s>In this way the small stones and gravel
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              flow down along the frame, and the sand mixed with particles of gold remains
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              in the pockets between the strips. </s>
              <s>When the contents of the pockets have
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              been shaken out and collected in one place, he washes them in a bowl and
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              thus cleans the gold dust.</s>
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              <s>Other people, among whom are the Lusitanians
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              16
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              , fix to the sides of a
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              sluice, which is about six feet long and a foot and a half broad, many cross­
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              strips or riffles, which project backward and are a digit apart. </s>
              <s>The washer
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              or his wife lets the water into the head of the sluice, where he throws the sand
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              which contains the particles of gold. </s>
              <s>As it flows down he agitates it with a
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              wooden scrubber, which he moves transversely to the riffles. </s>
              <s>He constantly
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              removes with a pointed wooden stick the sediment which settles in the pockets
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              between the riffles, and in this way the particles of gold settle in them,
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              while the sand and other valueless materials are carried by the water into a
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              tub placed below the sluice. </s>
              <s>He removes the particles of metal with a small
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              wooden shovel into a wooden bowl. </s>
              <s>This bowl does not exceed a foot and a
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              quarter in breadth, and by moving it up and down in the stream he cleanses
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              the gold dust, for the remaining sand flows out of the dish, and the gold dust
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              settles in the middle of it, where there is a cup-like depression. </s>
              <s>Some make
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              use of a bowl which is grooved inside like a shell, but with a smooth lip where
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              the water flows out. </s>
              <s>This smooth place, however, is narrower where the
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              grooves run into it, and broader where the water flows out.</s>
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