Galilei, Galileo, Mechanics, 1665

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    <archimedes>
      <text>
        <body>
          <chap>
            <pb xlink:href="070/01/005.jpg" pagenum="275"/>
            <p type="head">
              <s>DEFINITIONS.</s>
            </p>
            <p type="main">
              <s>That which in all Demonſtrative Sciences is neceſſary to be
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              obſerved, we ought alſo to follow in this Diſcourſe, that is;
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              to propound the Definitions of the proper Terms of this
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              Art, and the primary Suppoſitions, from which, as from ſeeds full
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              of fecundity, may of conſequence ſpring and reſult the cauſes,
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              and true Demonſtrations, of the Nature of all the Mechanick
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              Engines which are uſed, for the moſt part about the Motions of
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              Grave Matters, therefore we will determine, firſt, what is
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              GRA­
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              VITIE.
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              </s>
            </p>
            <p type="main">
              <s>We call
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              GRAVITIE
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              then, That propenſion of moving
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              naturally downwards, which is found in ſolid Bodies, cauſed by
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              the greater or leſſe quantity of matter, whereof they are conſti­
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              tuted.</s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              MOMENT
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              is the propenſion of deſcending, cauſed not ſo
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              much by the Gravity of the moveable, as by the diſpoſure which
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              divers Grave Bodies have in relation to one another; by means of
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              whichMoment, we oft ſee a Body leſs Grave counterpoiſe another
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              of greater Gravity: as in the Stiliard, a great Weight is raiſed by
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              a very ſmall counterpoiſe, not through exceſs of Gravity, but
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              through the remoteneſſe from the point whereby the Beam is up­
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              held, which conjoyned to the Gravity of the leſſer weight adds
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              thereunto Moment, and
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              Impetus
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              of deſcending, wherewith the
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              Moment of the other greater Gravity may be exceeded.
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              MO­
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              MENT
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              then is that IMPETUS of deſcending, compounded
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              of Gravity, Poſition, and the like, whereby that propenfion may
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              be occaſioned</s>
            </p>
            <p type="main">
              <s>The
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              CENTER
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              of
                <emph type="italics"/>
              GRAVITY
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              we define to be that point
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              in every Grave Body, about which conſiſt parts of equall Moment:
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              ſo that, imagining ſome Grave Body to be ſuſpended and ſuſtain­
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              ed by the ſaid point, the parts on the right hand will Equilibrate
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              thoſe on the left, the Anteriour, the Poſteriour, and thoſe above
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              thoſe below; ſo that be it in any whatſoever fite, and poſition,
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              provided it be ſuſpended by the ſaid
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              CENTER,
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              it ſhall ſtand
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              ſtill: and this is that point which would gladly unite with the
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              univerſall Center of Grave Bodies, namely withthat of the Earth,
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              if it might thorow ſome free
                <emph type="italics"/>
              Medium
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              deſcend thither. </s>
              <s>From
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              whence we take theſe Suppoſitions.</s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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