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

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      <text>
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          <chap>
            <p type="main">
              <s>
                <pb xlink:href="040/01/433.jpg" pagenum="411"/>
              derate the time, the Artificers that make them accomodate a
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              tain voluble ſtaffe horozontally, and at each end of it they
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              ſten two Weights of Lead, and when the time goeth too ſlow,
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              by the onely removing thoſe Leads a little nearer to the centre
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              of the ſtaffe, they render its vibrations more frequent; and on
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              the contrary to retard it, it is but drawing thoſe Weights more
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              towards the ends; for ſo the vibrations are made more ſeldome,
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              and conſequently the intervals of the hours are prolonged.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg801"/>
                <emph type="italics"/>
              The true
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              theſis may diſpatch
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              its revolutions in a
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              ſhorter time, in
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              leſſer circles than
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              in greater; the
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              which is proved by
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              two examples.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg802"/>
                <emph type="italics"/>
              The firſt
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              ample.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>Here the movent vertue is the ſame, namely the counterpoiſe,
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                <arrow.to.target n="marg803"/>
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              the moveables are thoſe ſame Weights of lead, and their
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              brations are more frequent when they are neerer to the centre,
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              that is, when they move by leſſer circles. </s>
              <s>Hanging equal
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              Weights at unequal cords, and being removed from their
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              pendicularity, letting them go; we ſhall ſee thoſe that are
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              dent at the ſhorter cords, to make their vibrations under ſhorter
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              times, as thoſe that move by leſſer circles. </s>
              <s>Again, let ſuch a
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              kind of Weight be faſtened to a cord, which cord let play upon
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              a ſtaple faſtened in the Seeling, and do you hold the other end
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              of the cord in your hand, and having given the motion to the
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              pendent Weight, whilſt it is making its vibrations, pull the
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              end of the cord that you hold in your hand, ſo that the Weight
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              may riſe higher and higher: In its riſing you ſhall ſee the
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              quency of its vibrations encreaſe, in regard that they are made
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              ſucceſſively by leſſer and leſſer circies. </s>
              <s>And here I deſire you to
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                <arrow.to.target n="marg804"/>
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              take notice of two particulars worthy to be obſerved. </s>
              <s>One is
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              that the vibrations of one of thoſe plummets are made with ſuch
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              a neceſſity under ſuch determinate times, that it is altogether
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              impoſſible to cauſe them to be made under other times, unleſſe
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              it be by prolonging, or abreviating the cord; of which you
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              may alſo at this very inſtant aſcertain your ſelves by experience,
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              tying a ſtone to a pack-threed, and holding the other end in
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              your hand, trying whether you can ever by any artifice be able
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              to ſwing it this way and that way in other than one determinate
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              time, unleſſe by lengthening or ſhortening the ſtring, which
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              you will find to be abſolutely impoſſible. </s>
              <s>The other particular
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              truly admirable is, that the ſelf ſame
                <emph type="italics"/>
              pendulum
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              makes its
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              tions with one and the ſame frequency, or very little, and as it
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              were inſenſibly different, whether they be made by very great,
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              or very ſmall arches of the ſelf-ſame circumference. </s>
              <s>I mean that
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              whether we remove the
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              pendulum
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              from perpendicularity one, two,
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              or three degrees onely, or whether we remove it 70. 80. nay to
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              an entire quadrant, it being let go, will in the one caſe and in
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              the other make its vibrations with the ſame frequency, as well
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              the former where it is to move by an arch of but four or ſix
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              grees, as the ſecond, where it is to paſſe arches of 160. or more </s>
            </p>
          </chap>
        </body>
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