Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

Table of figures

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      <text>
        <body>
          <chap>
            <p type="main">
              <s>
                <pb xlink:href="040/01/991.jpg" pagenum="297"/>
              the ſaid Cylinder the Helical Line deſcribed by the Line AEFGH,
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              which we vulgarly call the Wale of the Screw, which was produ­
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              ced by the Line A C. </s>
              <s>And in this manner is the Inſtrument made,
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              which is by the Greeks called
                <foreign lang="grc">Κόχλος,</foreign>
              and by us a Screw; which
                <lb/>
                <arrow.to.target n="marg1119"/>
                <lb/>
              winding about
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              cometh to work
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                <figure id="id.040.01.991.1.jpg" xlink:href="040/01/991/1.jpg" number="203"/>
                <lb/>
              and inſinu­
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              ate with its
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              Wales under
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              the Weight, and
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              with facility rai­
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              ſeth it. </s>
              <s>And we
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              having demon­
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              ſtrated, That up­
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              on [
                <emph type="italics"/>
              or along
                <emph.end type="italics"/>
              ]
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              the elevated Plane the Force hath the ſame proportion to the
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              Weight, that the perpendicular Altitude of the ſaid Plane hath to
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              its Length; ſo, ſuppoſing that the Force in the Screw A B C D is
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              multiplied according to the proportion by which the Length of the
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              whole Wale exceedeth the Altitude C B, from hence we come
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              to know that making the Screw with its Helix's more thick or cloſe
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              together, it becometh ſo much the more forceable, as being begot
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              by a Plane leſs elevated, and whoſe Length regards its own Per­
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              pendicular Altitude with greater proportion. </s>
              <s>But we will not
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              omit to advertiſe you, that deſiring to find the Force of a propo­
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              ſed Screw, it will not be needful that we meaſure the Length of
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              all its Wales, and the Altitude of the whole Cylinder, but it
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              will be enough if we ſhall but examine how many times the Di­
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              ſtance betwixt two ſingle and Contiguous terms do enter into one
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              ſole Turn of the ſame Wale, as for example, how many times
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              the Diſtance AF is contained in the Length of the Turn AEF:
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              For this is the ſame proportion that the Altitude CB hath to all
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              the Wale.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg1118"/>
                <emph type="italics"/>
              Levar in capo
                <emph.end type="italics"/>
                <lb/>
              ſignfieth to lift
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              on high by force</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg1119"/>
              *
                <foreign lang="grc">Κόχλος,</foreign>
              in La­
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              tine
                <emph type="italics"/>
              Cocblea,
                <emph.end type="italics"/>
              any
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              Screw winding
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              like the Shell of
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              a Snail.</s>
            </p>
            <p type="main">
              <s>If all that be underſtood which we have hitherto ſpoken touch­
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              ing the Nature of this Inſtrument, I do not doubt in the leaſt but
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              that all the other circumſtances may without difficulty be compre­
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              hended: as for inſtance, that inſteed of making the Weight to
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              mount upon the Screw if one accommodates its Nut with
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              the Helix incavated or made hollow, into which the Male Screw
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              that is the Wale entring, & then being turned round it raiſeth and
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              lifteth up the Nut or Male Screw together with the Weight which
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              was hanged thereat. </s>
              <s>Laſtly, we are not to paſs over that Conſidera­
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              tion with ſilence which at the beginning hath been ſaid to be neceſ­
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              ſary for us to have in all Mechanick Inſtruments, to wit, That
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              what is gained in Force by their aſſiſtance, is loſt again in Time, </s>
            </p>
          </chap>
        </body>
      </text>
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