Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div332" type="section" level="1" n="180">
          <pb o="92" file="0160" n="185" rhead="An ESSAY"/>
        </div>
        <div xml:id="echoid-div334" type="section" level="1" n="181">
          <head xml:id="echoid-head193" style="it" xml:space="preserve">II. When the Perſpective Plane is inclined.</head>
          <head xml:id="echoid-head194" xml:space="preserve">
            <emph style="sc">Prob</emph>
          . III.</head>
          <p style="it">
            <s xml:id="echoid-s2084" xml:space="preserve">115. </s>
            <s xml:id="echoid-s2085" xml:space="preserve">To find the Repreſentation of Figures which
              <lb/>
            are in the Geometrical Plane.</s>
            <s xml:id="echoid-s2086" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2087" xml:space="preserve">The Operation laid down for the
              <note symbol="*" position="left" xlink:label="note-0160-01" xlink:href="note-0160-01a" xml:space="preserve">109,
                <lb/>
              110.</note>
            Plane being perpendicular, may be uſed here,
              <lb/>
            becauſe the inclined perſpective Plane may be
              <lb/>
            changed into a perpendicular or upright one.</s>
            <s xml:id="echoid-s2088" xml:space="preserve"/>
          </p>
          <note symbol="*" position="left" xml:space="preserve">81.</note>
        </div>
        <div xml:id="echoid-div336" type="section" level="1" n="182">
          <head xml:id="echoid-head195" xml:space="preserve">
            <emph style="sc">Prob</emph>
          . IV.</head>
          <p style="it">
            <s xml:id="echoid-s2089" xml:space="preserve">116. </s>
            <s xml:id="echoid-s2090" xml:space="preserve">To find the Appearances of any Number of
              <lb/>
            Lines of the ſame Length, which are perpendicular
              <lb/>
            to the Geometrical Plane.</s>
            <s xml:id="echoid-s2091" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2092" xml:space="preserve">Raiſe a Perpendicular R C, in ſome Point on
              <lb/>
              <note position="left" xlink:label="note-0160-03" xlink:href="note-0160-03a" xml:space="preserve">Fig. 62.</note>
            the Baſe Line, in which aſſume R L equal in
              <lb/>
            Length to the given Lines; </s>
            <s xml:id="echoid-s2093" xml:space="preserve">and draw the Line
              <lb/>
            L P, through the Point L, ſo that the Angle
              <lb/>
            L P R, be equal to the Angle of Inclination of
              <lb/>
            the perſpective Plane; </s>
            <s xml:id="echoid-s2094" xml:space="preserve">then having made R S
              <lb/>
            equal to P L, and S C equal to P R, draw the
              <lb/>
            Lines S Q and C D, parallel to the Baſe Line.
              <lb/>
            </s>
            <s xml:id="echoid-s2095" xml:space="preserve">This being done, raiſe up the Figures of the
              <lb/>
            Geometrical Plane, ſo that the Point R coincides
              <lb/>
            with c, and the Line R H, with C D; </s>
            <s xml:id="echoid-s2096" xml:space="preserve">then
              <lb/>
            proceed as is directed for the
              <note symbol="*" position="left" xlink:label="note-0160-04" xlink:href="note-0160-04a" xml:space="preserve">112, 113.</note>
            perſpective Plane, in uſing S Q for the Baſe
              <lb/>
            Line.</s>
            <s xml:id="echoid-s2097" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2098" xml:space="preserve">This is demonſtrated in n. </s>
            <s xml:id="echoid-s2099" xml:space="preserve">114.</s>
            <s xml:id="echoid-s2100" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div338" type="section" level="1" n="183">
          <head xml:id="echoid-head196" xml:space="preserve">
            <emph style="sc">Remarks</emph>
          .</head>
          <p>
            <s xml:id="echoid-s2101" xml:space="preserve">The Point C muſt be aſſumed below the Point
              <lb/>
            S, when the perſpective Plane is inclined </s>
          </p>
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