Gravesande, Willem Jacob 's, An essay on perspective

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          <p>
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              <pb o="16" file="0036" n="37" rhead="An ESSAY"/>
            for then, what is on the Right, will appear on
              <lb/>
            the Left.</s>
            <s xml:id="echoid-s501" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s502" xml:space="preserve">Therefore, I lay my Perſpective Plane upon
              <lb/>
            the Geometrical Plane; </s>
            <s xml:id="echoid-s503" xml:space="preserve">ſo that it be between
              <lb/>
            the Horizontal Plane, and the Figures requir’d
              <lb/>
            to be thrown into Perſpective.</s>
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        <div xml:id="echoid-div55" type="section" level="1" n="27">
          <head xml:id="echoid-head29" xml:space="preserve">
            <emph style="sc">Problem</emph>
          I.</head>
          <p style="it">
            <s xml:id="echoid-s505" xml:space="preserve">22. </s>
            <s xml:id="echoid-s506" xml:space="preserve">To find the Appearance of a Point, which is in
              <lb/>
            the Geometrical Plane.</s>
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          </p>
          <p>
            <s xml:id="echoid-s508" xml:space="preserve">Let Z be the Geometrical Plane, I E the Baſe
              <lb/>
              <note position="left" xlink:label="note-0036-01" xlink:href="note-0036-01a" xml:space="preserve">Fig. 7.</note>
            Line, D V the Horizontal Line, V the Point
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            of Sight, D one of the Points of Diſtance, and
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            A the given Point.</s>
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        <div xml:id="echoid-div57" type="section" level="1" n="28">
          <head xml:id="echoid-head30" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s510" xml:space="preserve">From the Point A, let fall the Perpendicular
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            A B upon the Baſe Line; </s>
            <s xml:id="echoid-s511" xml:space="preserve">and from the Point of
              <lb/>
            Concurrence B, draw the Line B V to the Point
              <lb/>
            of Sight; </s>
            <s xml:id="echoid-s512" xml:space="preserve">then aſſume B E in the Baſe Line
              <lb/>
            equal to B A, and from the Point E draw the
              <lb/>
            Line E D to the Point of Diſtance D: </s>
            <s xml:id="echoid-s513" xml:space="preserve">And the
              <lb/>
            Point (a), the Interſection of B V and E D, is
              <lb/>
            the Repreſentation ſought.</s>
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          </p>
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        <div xml:id="echoid-div58" type="section" level="1" n="29">
          <head xml:id="echoid-head31" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s515" xml:space="preserve">23. </s>
            <s xml:id="echoid-s516" xml:space="preserve">The Appearance of the Line A B, is a Part of the Line B V. </s>
            <s xml:id="echoid-s517" xml:space="preserve">Now, if we conceive a Line
              <lb/>
              <note symbol="*" position="left" xlink:label="note-0036-02" xlink:href="note-0036-02a" xml:space="preserve">16.</note>
            iſſuing from the Eye towards the Point D, and
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            another from the Point A towards the Point E;
              <lb/>
            </s>
            <s xml:id="echoid-s518" xml:space="preserve">theſe two Lines will be parallel, becauſe they
              <lb/>
            are in parallel Planes, aud each make half a
              <lb/>
            right Angle with the Perſpective Plane; </s>
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