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

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            <p type="main">
              <s>
                <pb xlink:href="040/01/242.jpg" pagenum="224"/>
              and you had no other object viſible and ſtable, wherewith to make
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              compariſons to that, you could not perceive its motion?</s>
            </p>
            <p type="main">
              <s>SIMP. No, nor the ſtone it ſelf; for if I would ſee it, when
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                <arrow.to.target n="marg429"/>
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              it is at the higheſt, I muſt raiſe up my head, and as it deſcendeth
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              I muſt hold it lower and lower, and in a word, muſt continually
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              move either that, or my eyes, following the motion of the ſaid
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              ſtone.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg429"/>
                <emph type="italics"/>
              Whence the
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              tion of a cadent
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              dy is collected.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>SALV. </s>
              <s>You have now rightly anſwered: you know then that
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                <arrow.to.target n="marg430"/>
                <lb/>
              the ſtone lyeth ſtill, when without moving your eye, you alwayes
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              ſee it before you; and you know that it moveth, when for the
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              keeping it in ſight, you muſt move the organ of ſight, the eye. </s>
              <s>So
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              then when ever without moving your eye, you continually
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              hold an object in the ſelf ſame aſpect, you do always judge it
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              immoveable.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg430"/>
                <emph type="italics"/>
              The motion of
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              the eye argueth
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              the motion of the
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              object looked on.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>SIMP. </s>
              <s>I think it muſt needs be ſo.</s>
            </p>
            <p type="main">
              <s>SALV. </s>
              <s>Now fancy your ſelf to be in a ſhip, and to have fixed
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              your eye on the point of the Sail-yard: Do you think, that
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              cauſe the ſhip moveth very faſt, you muſt move your eye, to keep
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              your ſight alwayes upon the point of the Sail-yard, and to
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              low its motion?</s>
            </p>
            <p type="main">
              <s>SIMP. </s>
              <s>I am certain, that I ſhould need to make no change at
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              all; and that not only in the ſight; but if I had aimed a Musket
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              at it, I ſhould never have need, let the ſhip move how it will,
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              to ſtir it an hairs breadth to keep it full upon the ſame.</s>
            </p>
            <p type="main">
              <s>SALV. </s>
              <s>And this happens becauſe the motion, which the Ship
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              conferreth on the Sail-yard, it conferreth alſo upon you, and upon
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              your eye; ſo that you need not ſtir it a jot to behold the top of
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              the Sail-yard: and conſequently, it will ſeem to you
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              able. </s>
              <s>Now this Diſcourſe being applied to the revolution of the
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              Earth, and to the ſtone placed in the top of the Tower, in which
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              you cannot diſcern any motion, becauſe that you have that
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              tion which is neceſſary for the following of it, in common with it
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              from the Earth; ſo that you need not move your eye. </s>
              <s>When
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              gain there is conferred upon it the motion of deſcent, which is its
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              particular motion, and not yours, and that it is intermixed with the
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              circular, that part of the circular which is common to the ſtone,
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              and to the eye, continueth to be imperceptible, and the right
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              ly is perceived, for that to the perception of it, you muſt follow it
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              with your eye, looking lower and lower. </s>
              <s>I wiſh for the
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              ving of this Philoſopher, that I could adviſe him, that ſome time
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                <arrow.to.target n="marg431"/>
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              or other going by water, he would carry along with him a Veſſel
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              of reaſonable depth full of water, and prepare a ball of wax, or
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              other matter that would deſcend very ſlowly to the bottome, ſo
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              that in a minute of an hour, it would ſcarce ſink a yard; and that
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              rowing the boat as faſt as could be, ſo that in a minute of an hour </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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