Agricola, Georgius
,
De re metallica
,
1912/1950
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<
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<
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<
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pagenum
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184
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to the shaft timbers. </
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>
<
s
>This machine draws the water higher, as much as
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twenty-four feet. </
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>
<
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>If the diameter of the pipes is large, only two pumps are
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made; if smaller, three, so that by either method the volume of water is the
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same. </
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>
<
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>This also must be understood regarding the other machines and
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their pipes. </
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<
s
>Since these pumps are composed of two lengths of pipe, the
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little iron box having the iron valve which I described before, is not enclosed
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in a trunk, but is in the lower length of pipe, at that point where it joins
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the upper one; thus the rounded part of the piston-rod is only as long as
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the upper length of pipe; but I will presently explain this more clearly.</
s
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</
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<
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>The sixth kind of pump would be just the same as the fifth were it not
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that it has an axle instead of a barrel, turned not by men but by a water
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wheel, which is revolved by the force of water striking its buckets.
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</
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<
s
>Since water-power far exceeds human strength, this machine draws water
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through its pipes by discs out of a shaft more than one hundred feet deep.
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</
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<
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>The bottom of the lowest pipe, set in the sump, not only of this pump but
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also of the others, is generally enclosed in a basket made of wicker-work, to
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prevent wood shavings and other things being sucked in. (See p. </
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<
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>183.)</
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<
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>The seventh kind of pump, invented ten years ago, which is the most
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ingenious, durable, and useful of all, can be made without much expense. </
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>
<
s
>It
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is composed of several pumps, which do not, like those last described, go down
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into the shaft together, but of which one is below the other, for if there are
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three, as is generally the case, the lower one lifts the water of the sump and
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pours it out into the first tank; the second pump lifts again from that tank
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into a second tank, and the third pump lifts it into the drain of the tunnel.
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</
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<
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>A wheel fifteen feet high raises the piston-rods of all these pumps at the same
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time and causes them to drop together. </
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>
<
s
>The wheel is made to revolve by
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paddles, turned by the force of a stream which has been diverted to the
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mountain. </
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>
<
s
>The spokes of the water-wheel are mortised in an axle six feet
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long and one foot thick, each end of which is surrounded by an iron band,
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but in one end there is fixed an iron journal; to the other end is attached an
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iron like this journal in its posterior part, which is a digit thick and as wide
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as the end of the axle itself. </
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>
<
s
>Then the iron extends horizontally, being
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rounded and about three digits in diameter, for the length of a foot, and
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serves as a journal; thence, it bends to a height of a foot in a curve,
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like the horn of the moon, after which it again extends straight out for
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one foot; thus it comes about that this last straight portion, as it
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revolves in an orbit becomes alternately a foot higher and a foot lower than
<
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the first straight part. </
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>
<
s
>From this round iron crank there hangs the first flat
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pump-rod, for the crank is fixed in a perforation in the upper end of this flat
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lb
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pump-rod just as the iron key of the first set of “claws” is fixed into the
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lower end. </
s
>
<
s
>In order to prevent the pump-rod from slipping off it, as it
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lb
/>
could easily do, and that it may be taken off when necessary, its opening
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lb
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is wider than the corresponding part of the crank, and it is fastened on
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both sides by iron keys. </
s
>
<
s
>To prevent friction, the ends of the pump-rods are
<
lb
/>
protected by iron plates or intervening leathers. </
s
>
<
s
>This first pump-rod is
<
lb
/>
about twelve feet long, the other two are twenty-six feet, and each is a palm </
s
>
</
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</
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</
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</
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