Gravesande, Willem Jacob 's, An essay on perspective

Table of Notes

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          <pb o="66" file="0120" n="138" rhead="An ESSAY"/>
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        <div xml:id="echoid-div232" type="section" level="1" n="122">
          <head xml:id="echoid-head128" xml:space="preserve">
            <emph style="sc">Problem</emph>
          II.</head>
          <p style="it">
            <s xml:id="echoid-s1580" xml:space="preserve">82. </s>
            <s xml:id="echoid-s1581" xml:space="preserve">To find the Appearance of a Point above the
              <lb/>
            Geometrical Plane.</s>
            <s xml:id="echoid-s1582" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1583" xml:space="preserve">Let H C be the Baſe Line: </s>
            <s xml:id="echoid-s1584" xml:space="preserve">And let T be the
              <lb/>
              <note position="left" xlink:label="note-0120-01" xlink:href="note-0120-01a" xml:space="preserve">Fig. 45.</note>
            accidental Point of the Lines perpendicular
              <lb/>
            to the Geometrical Plane. </s>
            <s xml:id="echoid-s1585" xml:space="preserve">This Point will
              <lb/>
            be in that Place of the Vertical Line,
              <note symbol="*" position="left" xlink:label="note-0120-02" xlink:href="note-0120-02a" xml:space="preserve">13.</note>
            it is cut by the Prolongation of the Line mea-
              <lb/>
            ſuring the Height of the Eye; </s>
            <s xml:id="echoid-s1586" xml:space="preserve">for this laſt
              <lb/>
            Line is parallel to the ſaid Perpendiculars. </s>
            <s xml:id="echoid-s1587" xml:space="preserve">And
              <lb/>
            ſo likewiſe the aforeſaid Point is the ſame as
              <lb/>
            the Point T of Fig. </s>
            <s xml:id="echoid-s1588" xml:space="preserve">44: </s>
            <s xml:id="echoid-s1589" xml:space="preserve">Let V be the Point of
              <lb/>
            Sight, S the Station Point, and Q the Station
              <lb/>
            Point of the upright perſpective Plane, to which
              <lb/>
            the inclined perſpective Plane is reduced . </s>
            <s xml:id="echoid-s1590" xml:space="preserve">
              <note symbol="*" position="left" xlink:label="note-0120-03" xlink:href="note-0120-03a" xml:space="preserve">81.</note>
            laſtly, let A be the Seat of the given Point.</s>
            <s xml:id="echoid-s1591" xml:space="preserve"/>
          </p>
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        <div xml:id="echoid-div234" type="section" level="1" n="123">
          <head xml:id="echoid-head129" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1592" xml:space="preserve">Draw two Lines M P and P E ſeparately,
              <lb/>
            making a right Angle with each other; </s>
            <s xml:id="echoid-s1593" xml:space="preserve">in one
              <lb/>
            of which, aſſume P E, equal to the Height of
              <lb/>
            the given Point, whoſe Perſpective is ſought;
              <lb/>
            </s>
            <s xml:id="echoid-s1594" xml:space="preserve">and draw the Line E M, making an Angle with
              <lb/>
            M P, equal to the Angle of Inclination of the
              <lb/>
            perſpective Plane. </s>
            <s xml:id="echoid-s1595" xml:space="preserve">Again let fall the Perpen-
              <lb/>
            dicular A D from the Point A to the Baſe
              <lb/>
            Line, in which aſſume A L equal to P M, to-
              <lb/>
            wards the Baſe Line, when the perſpective
              <lb/>
            Plane is inclined towards the Objects (as we
              <lb/>
            have here ſuppoſed) but on the other Side of A,
              <lb/>
            when the perſpective Plane inclines towards the
              <lb/>
            Eye. </s>
            <s xml:id="echoid-s1596" xml:space="preserve">Then from the Point A, draw a Line
              <lb/>
            to the Point S, cutting the Baſe Line in B, and
              <lb/>
            joyn the Points L and Q, by a Line cutting the
              <lb/>
            Baſe Line in C. </s>
            <s xml:id="echoid-s1597" xml:space="preserve">This being done, draw </s>
          </p>
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