Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div182" type="section" level="1" n="96">
          <pb o="54" file="0100" n="114" rhead="An ESSAY"/>
        </div>
        <div xml:id="echoid-div184" type="section" level="1" n="97">
          <head xml:id="echoid-head103" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1303" xml:space="preserve">In ſome ſeparate Place, draw the Lines C E
              <lb/>
            and C P, making an Angle with each other
              <lb/>
            equal to the Angle of Inclination of the given
              <lb/>
            Line; </s>
            <s xml:id="echoid-s1304" xml:space="preserve">and in one of theſe Lines, aſſume C E
              <lb/>
            equal to the given Line, and let fall the Perpen-
              <lb/>
            dicular E P, from the Point E upon the other
              <lb/>
            Line. </s>
            <s xml:id="echoid-s1305" xml:space="preserve">Then aſſume A B, in the Direction of
              <lb/>
            the propos’d Line, equal to C P; </s>
            <s xml:id="echoid-s1306" xml:space="preserve">and after ha-
              <lb/>
            ving found a, the Perſpective of A, and the
              <lb/>
            Point T , the Perſpective of a Point
              <note symbol="*" position="left" xlink:label="note-0100-01" xlink:href="note-0100-01a" xml:space="preserve">50.</note>
            above B, the Height of P E; </s>
            <s xml:id="echoid-s1307" xml:space="preserve">join the Points a
              <lb/>
            and T by a right Line; </s>
            <s xml:id="echoid-s1308" xml:space="preserve">and the ſought Appear-
              <lb/>
            ance will be had.</s>
            <s xml:id="echoid-s1309" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div186" type="section" level="1" n="98">
          <head xml:id="echoid-head104" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1310" xml:space="preserve">If from the Extremity of the inclin’d Line, a
              <lb/>
            Perpendicular be let fall upon the Geometrical
              <lb/>
            Plane, the ſaid Perpendicular will meet this
              <lb/>
            Plane in the Point B, and will be equal to P E;
              <lb/>
            </s>
            <s xml:id="echoid-s1311" xml:space="preserve">as is evident by the Conſtruction of the Figure
              <lb/>
            C P E. </s>
            <s xml:id="echoid-s1312" xml:space="preserve">But the Point T is the Repreſentation
              <lb/>
            of the Extremity of this Perpendicular; </s>
            <s xml:id="echoid-s1313" xml:space="preserve">and
              <lb/>
            therefore it is alſo the Extremity of the inclin’d
              <lb/>
            Line. </s>
            <s xml:id="echoid-s1314" xml:space="preserve">Which was to be demonſtrated.</s>
            <s xml:id="echoid-s1315" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div187" type="section" level="1" n="99">
          <head xml:id="echoid-head105" xml:space="preserve">
            <emph style="sc">Remarks</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1316" xml:space="preserve">There are ſome Caſes of this Propoſition, that
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            may be ſhorten’d. </s>
            <s xml:id="echoid-s1317" xml:space="preserve">As, 1. </s>
            <s xml:id="echoid-s1318" xml:space="preserve">When there are ſeve-
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            ral Lines of this Kind parallel between them-
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            ſelves, and whoſe accidental Point can be
              <lb/>
            found : </s>
            <s xml:id="echoid-s1319" xml:space="preserve">And, 2. </s>
            <s xml:id="echoid-s1320" xml:space="preserve">When an inclin’d Line is
              <note symbol="*" position="left" xlink:label="note-0100-02" xlink:href="note-0100-02a" xml:space="preserve">68.</note>
            rallel to the perſpective Plane. </s>
            <s xml:id="echoid-s1321" xml:space="preserve">The Manner </s>
          </p>
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