Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div192" type="section" level="1" n="102">
          <p>
            <s xml:id="echoid-s1341" xml:space="preserve">
              <pb o="56" file="0102" n="116" rhead="An ESSAY"/>
            through I, and the Extremity of the propoſed
              <lb/>
            Line; </s>
            <s xml:id="echoid-s1342" xml:space="preserve">and therefore the Perſpective of this Ex-
              <lb/>
            tremity is in the Line L H; </s>
            <s xml:id="echoid-s1343" xml:space="preserve">which was to be
              <lb/>
            demonſtrated.</s>
            <s xml:id="echoid-s1344" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1345" xml:space="preserve">Note, if F H had been aſſumed, the one half,
              <lb/>
            or one third, & </s>
            <s xml:id="echoid-s1346" xml:space="preserve">c. </s>
            <s xml:id="echoid-s1347" xml:space="preserve">of what it is; </s>
            <s xml:id="echoid-s1348" xml:space="preserve">then it is mani-
              <lb/>
            feſt that R Q muſt alfo have been taken
              <note symbol="*" position="left" xlink:label="note-0102-01" xlink:href="note-0102-01a" xml:space="preserve">19.</note>
            to the one half, or third Part, & </s>
            <s xml:id="echoid-s1349" xml:space="preserve">c. </s>
            <s xml:id="echoid-s1350" xml:space="preserve">of C E.</s>
            <s xml:id="echoid-s1351" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div196" type="section" level="1" n="103">
          <head xml:id="echoid-head109" xml:space="preserve">
            <emph style="sc">Method</emph>
          . III.</head>
          <p style="it">
            <s xml:id="echoid-s1352" xml:space="preserve">71. </s>
            <s xml:id="echoid-s1353" xml:space="preserve">Forinclined Lines not meeting the Geometrical
              <lb/>
            Plane.</s>
            <s xml:id="echoid-s1354" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1355" xml:space="preserve">Let A and B be the Seats of the Extremities of
              <lb/>
              <note position="left" xlink:label="note-0102-02" xlink:href="note-0102-02a" xml:space="preserve">Fig. 37.</note>
            the given Line. </s>
            <s xml:id="echoid-s1356" xml:space="preserve">Let X repreſent a Plane paſſing
              <lb/>
            through the given Line perpendicular to the
              <lb/>
            Geometrical Plane. </s>
            <s xml:id="echoid-s1357" xml:space="preserve">Likewiſe let M N in this
              <lb/>
            Plane, repreſent the Line whoſe Perſpective is re-
              <lb/>
            quir’d; </s>
            <s xml:id="echoid-s1358" xml:space="preserve">and let C N and P M be perpendicular to
              <lb/>
            the Geometrical Plane: </s>
            <s xml:id="echoid-s1359" xml:space="preserve">Whence P C repreſents
              <lb/>
            A B, and conſequently is equal thereto.</s>
            <s xml:id="echoid-s1360" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div198" type="section" level="1" n="104">
          <head xml:id="echoid-head110" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1361" xml:space="preserve">Find the Point I , the Perſpective of a
              <note symbol="*" position="left" xlink:label="note-0102-03" xlink:href="note-0102-03a" xml:space="preserve">50.</note>
            above the Point A, the Height of C N; </s>
            <s xml:id="echoid-s1362" xml:space="preserve">and
              <lb/>
            draw the Line B S, from the Point B, to the
              <lb/>
            Station Point I, cutting the Baſe Line in E; </s>
            <s xml:id="echoid-s1363" xml:space="preserve">and
              <lb/>
            from the Point I, draw a Line to the accidental
              <lb/>
            Point F; </s>
            <s xml:id="echoid-s1364" xml:space="preserve">which cut by a Perpendicular to the
              <lb/>
            Baſe Line, raiſed at the Point E; </s>
            <s xml:id="echoid-s1365" xml:space="preserve">and then I T
              <lb/>
            will be the Appearance ſought.</s>
            <s xml:id="echoid-s1366" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div200" type="section" level="1" n="105">
          <head xml:id="echoid-head111" xml:space="preserve">
            <emph style="sc">Method</emph>
          IV.</head>
          <p style="it">
            <s xml:id="echoid-s1367" xml:space="preserve">72. </s>
            <s xml:id="echoid-s1368" xml:space="preserve">For inclined Lines parallel to the perſpective
              <lb/>
            Plane.</s>
            <s xml:id="echoid-s1369" xml:space="preserve"/>
          </p>
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