Agricola, Georgius, De re metallica, 1912/1950
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              stream can turn it. </s>
              <s>This water, falling into a race, runs therefrom on to a
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              second high and heavy wheel of a lower machine, whose pump lifts the water
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              out of a deep shaft. </s>
              <s>Since, however, the water of so small a stream cannot
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              alone revolve the lower water-wheel, the axle of the latter is turned at the start
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              with a crank worked by two men, but as soon as it has poured out into a pool
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              the water which has been drawn up by the pumps, the upper wheel draws
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              up this water by its own pump, and pours it into the race, from which it
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              flows on to the lower water-wheel and strikes its buckets. </s>
              <s>So both this
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              water from the mine, as well as the water of the stream, being turned down
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              the races on to that subterranean wheel of the lower machine, turns it, and
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              water is pumped out of the deeper part of the shaft by means of two or
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              three pumps.
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              16
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              <s>If the stream supplies enough water straightway to turn a higher and
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              heavier water-wheel, then a toothed drum is fixed to the other end of the
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              axle, and this turns the drum made of rundles on another axle set below it.
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              <s>To each end of this lower axle there is fitted a crank of round iron curved
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              like the horns of the moon, of the kind employed in machines of this
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              description. </s>
              <s>This machine, since it has rows of pumps on each side,
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              draws great quantities of water.</s>
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              <s>Of the rag and chain pumps there are six kinds known to us, of which
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              the first is made as follows: A cave is dug under the surface of earth or in a
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              tunnel, and timbered on all sides by stout posts and planks, to prevent either
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              the men from being crushed or the machine from being broken by its collapse.
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              <s>In this cave, thus timbered, is placed a water-wheel fitted to an angular axle.
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              <s>The iron journals of the axle revolve in iron pillows, which are held in timbers
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              of sufficient strength. </s>
              <s>The wheel is generally twenty-four feet high,
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              occasionally thirty, and in no way different from those which are made for
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              grinding corn, except that it is a little narrower. </s>
              <s>The axle has on one side
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              a drum with a groove in the middle of its circumference, to which are fixed
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              many four-curved iron clamps. </s>
              <s>In these clamps catch the links of the chain,
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              which is drawn through the pipes out of the sump, and which again falls,
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              through a timbered opening, right down to the bottom into the sump to a
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              balancing drum. </s>
              <s>There is an iron band around the small axle of the
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              balancing drum, each journal of which revolves in an iron bearing fixed to a
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              timber. </s>
              <s>The chain turning about this drum brings up the water by the
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              balls through the pipes. </s>
              <s>Each length of pipe is encircled and protected by
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              five iron bands, a palm wide and a digit thick, placed at equal distances from
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              each other; the first band on the pipe is shared in common with the
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              preceding length of pipe into which it is fitted, the last band with the succeed­
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              ing length of pipe which is fitted into it. </s>
              <s>Each length of pipe, except the
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              first, is bevelled on the outer circumference of the upper end to a distance
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              of seven digits and for a depth of three digits, in order that it may be inserted
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              into the length of pipe which goes before it; each, except the last, is reamed
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              out on the inside of the lower end to a like distance, but to the depth </s>
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