Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div132" type="section" level="1" n="73">
          <p>
            <s xml:id="echoid-s941" xml:space="preserve">
              <pb o="37" file="0075" n="85" rhead="on PERSPECTIVE."/>
            Point A parallel to the Baſe Line, and made e-
              <lb/>
            qual to B C. </s>
            <s xml:id="echoid-s942" xml:space="preserve">Now if from the Extremities of
              <lb/>
            the ſaid Line A L, Perpendiculars are let fall,
              <lb/>
            meeting the Baſe Line in the Points P and M,
              <lb/>
            and from theſe Points, Lines are drawn to the
              <lb/>
            Point of Sight V; </s>
            <s xml:id="echoid-s943" xml:space="preserve">then a N will likewiſe be
              <note symbol="*" position="right" xlink:label="note-0075-01" xlink:href="note-0075-01a" xml:space="preserve">5, 16.</note>
            the Perſpective of A L; </s>
            <s xml:id="echoid-s944" xml:space="preserve">and ſince P M is equal
              <lb/>
            to D E, a N will be likewiſe equal to G H, and
              <lb/>
            conſequently a N will be likewiſe equal to a I,
              <lb/>
            which is equal to G H.</s>
            <s xml:id="echoid-s945" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div134" type="section" level="1" n="74">
          <head xml:id="echoid-head80" xml:space="preserve">
            <emph style="sc">Method</emph>
          II.</head>
          <p>
            <s xml:id="echoid-s946" xml:space="preserve">57. </s>
            <s xml:id="echoid-s947" xml:space="preserve">The ſame Things being given, as in the
              <lb/>
            precedent Method, about the Point A, as a
              <lb/>
              <note position="right" xlink:label="note-0075-02" xlink:href="note-0075-02a" xml:space="preserve">Fig. 23.</note>
            Center, and with the Radius B C, deſcribe the
              <lb/>
            Arc of a Circle L M, and draw the Line O L
              <lb/>
            from the Eye touching it; </s>
            <s xml:id="echoid-s948" xml:space="preserve">then about a, (which
              <lb/>
            is the Repreſentation of A) as a Center deſcribe
              <lb/>
            the Circular Arc G I touching the Line L O,
              <lb/>
            and cutting another Line drawn through a Per-
              <lb/>
            pendicular to the Baſe Line in the Point I: </s>
            <s xml:id="echoid-s949" xml:space="preserve">I
              <lb/>
            ſay the Point I is the Extremity of the Repre-
              <lb/>
            ſentation ſought.</s>
            <s xml:id="echoid-s950" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div136" type="section" level="1" n="75">
          <head xml:id="echoid-head81" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s951" xml:space="preserve">To prove this, let fall the Perpendiculars A L
              <lb/>
            and a G upon the Line O L, which will meet
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            the ſaid Line in the Points wherein it touches
              <lb/>
            the circular Arcs M L and G I.</s>
            <s xml:id="echoid-s952" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s953" xml:space="preserve">Alſo aſſume D E in the Baſe Line equal to B C
              <lb/>
            or A L, and draw the Line D F; </s>
            <s xml:id="echoid-s954" xml:space="preserve">then through a,
              <lb/>
            draw a H parallel to the Baſe Line.</s>
            <s xml:id="echoid-s955" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s956" xml:space="preserve">Now let us conſider the Figure X, which re-
              <lb/>
              <note position="right" xlink:label="note-0075-03" xlink:href="note-0075-03a" xml:space="preserve">Fig. 24.</note>
            preſents a Plane paſſing through the Eye and
              <lb/>
            the Point A of the foregoing Figure, wherein
              <lb/>
            O f here, repreſents O F there; </s>
            <s xml:id="echoid-s957" xml:space="preserve">f e here, F </s>
          </p>
        </div>
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