Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
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            <p type="caption">
              <s>
                <pb pagenum="200"/>
              is broken and part of the chain or anything else should fall down; he guides
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              the bag with a wooden shovel, and fills it with water if it fails to take
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              in the water spontaneously. </s>
              <s>In these days, they sew an iron band into the
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              top of each bag that it may constantly remain open, and when lowered into
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              the sump may fill itself with water, and there is no need for a man to act as
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              governor of the bags. </s>
              <s>Further, in these days, of those men who stand on
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              the floor the one empties the bags, and the other closes the gates of the
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              reservoir and opens them again, and the same man usually fixes the large
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              hook in the link of the chain. </s>
              <s>In this way, three men only are employed in
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              working this machine; or even—since sometimes the one who empties the
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              bag presses the brake which is raised against the other drum and thus stops
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              the wheel—two men take upon themselves the whole labour.</s>
            </p>
            <p type="main">
              <s>But enough of haulage machines; I will now speak of ventilating
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              machines. </s>
              <s>If a shaft is very deep and no tunnel reaches to it, or no drift
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              from another shaft connects with it, or when a tunnel is of great length and
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              no shaft reaches to it, then the air does not replenish itself. </s>
              <s>In such a case it
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              weighs heavily on the miners, causing them to breathe with difficulty, and
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              sometimes they are even suffocated, and burning lamps are also extinguished.
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              </s>
              <s>There is, therefore, a necessity for machines which the Greeks call
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                <foreign lang="grc">πνευματικάι</foreign>
              and the Latins
                <emph type="italics"/>
              spiritales
                <emph.end type="italics"/>
              —though they do not give forth any
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              sound—which enable the miners to breathe easily and carry on their work.</s>
            </p>
            <p type="main">
              <s>These devices are of three genera. </s>
              <s>The first receives and diverts into
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              the shaft the blowing of the wind, and this genus is divided into three species,
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              of which the first is as follows. </s>
              <s>Over the shaft—to which no tunnel connects—
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              are placed three sills a little longer than the shaft, the first over the front,
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              the second over the middle, and the third over the back of the shaft. </s>
              <s>Their
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              ends have openings, through which pegs, sharpened at the bottom, are driven
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              deeply into the ground so as to hold them immovable, in the same way that
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              the sills of the windlass are fixed. </s>
              <s>Each of these sills is mortised into each
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              of three cross-beams, of which one is at the right side of the shaft, the second
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              at the left, and the third in the middle. </s>
              <s>To the second sill and the second
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              cross-beam—each of which is placed over the middle of the shaft—planks
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              are fixed which are joined in such a manner that the one which precedes
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              always fits into the groove of the one which follows. </s>
              <s>In this way four angles
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              and the same number of intervening hollows are created, which collect the
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              winds that blow from all directions. </s>
              <s>The planks are roofed above with a
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              cover made in a circular shape, and are open below, in order that the wind may
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              not be diverted upward and escape, but may be carried downward; and there­
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              by the winds of necessity blow into the shafts through these four openings.
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              </s>
              <s>However, there is no need to roof this kind of machine in those localities in
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              which it can be so placed that the wind can blow down through its topmost
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              part.</s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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