Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div252" type="section" level="1" n="132">
          <pb o="71" file="0127" n="146" rhead="on PERSPECTIVE."/>
        </div>
        <div xml:id="echoid-div254" type="section" level="1" n="133">
          <head xml:id="echoid-head139" xml:space="preserve">
            <emph style="sc">Remark</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1708" xml:space="preserve">It is manifeſt , that T R may be
              <note symbol="*" position="right" xlink:label="note-0127-01" xlink:href="note-0127-01a" xml:space="preserve">19.</note>
            equal to {1/2} or {1/3} & </s>
            <s xml:id="echoid-s1709" xml:space="preserve">c. </s>
            <s xml:id="echoid-s1710" xml:space="preserve">of what it is taken here,
              <lb/>
            provided likewiſe that then D N be aſſumed
              <lb/>
            equal to a correſpondent Part of the propoſed
              <lb/>
            Line.</s>
            <s xml:id="echoid-s1711" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div256" type="section" level="1" n="134">
          <head xml:id="echoid-head140" xml:space="preserve">
            <emph style="sc">Problem</emph>
          IV.</head>
          <p>
            <s xml:id="echoid-s1712" xml:space="preserve">87. </s>
            <s xml:id="echoid-s1713" xml:space="preserve">To throw a Sphere into Perſpective.</s>
            <s xml:id="echoid-s1714" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1715" xml:space="preserve">The Method of ſolving this Problem before
              <lb/>
            laid down , muſt be uſed here, but with
              <note symbol="*" position="right" xlink:label="note-0127-02" xlink:href="note-0127-02a" xml:space="preserve">63.</note>
            Difference; </s>
            <s xml:id="echoid-s1716" xml:space="preserve">that inſtead of uſing the Point of
              <lb/>
            Sight, the Point wherein a Perpendicular drawn
              <lb/>
            from the Eye to the perſpective Plane, meets
              <lb/>
            the ſaid Plane, muſt be uſed. </s>
            <s xml:id="echoid-s1717" xml:space="preserve">And you muſt
              <lb/>
            obſerve, that this Perpendicular meaſures the
              <lb/>
            Eye’s Diſtance from the perſpective Plane.</s>
            <s xml:id="echoid-s1718" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div258" type="section" level="1" n="135">
          <head xml:id="echoid-head141" xml:space="preserve">
            <emph style="sc">Problem</emph>
          V.</head>
          <p style="it">
            <s xml:id="echoid-s1719" xml:space="preserve">88. </s>
            <s xml:id="echoid-s1720" xml:space="preserve">To find the accidental Point of any Number
              <lb/>
              <note position="right" xlink:label="note-0127-03" xlink:href="note-0127-03a" xml:space="preserve">Fig. 48.</note>
            of Lines inclined to the Geometrical Plane.</s>
            <s xml:id="echoid-s1721" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1722" xml:space="preserve">Let A B be the Direction of one of the in-
              <lb/>
            clined Lines, O the Eye in the Horizontal Plane,
              <lb/>
            and S the Station Point.</s>
            <s xml:id="echoid-s1723" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div260" type="section" level="1" n="136">
          <head xml:id="echoid-head142" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1724" xml:space="preserve">Draw the Line O D, thro’ the Eye O parallel
              <lb/>
            to A B, meeting the Horizontal Line in D, which
              <lb/>
            will be the Accidental Point of the
              <note symbol="*" position="right" xlink:label="note-0127-04" xlink:href="note-0127-04a" xml:space="preserve">13, 14.</note>
            of the given Line; </s>
            <s xml:id="echoid-s1725" xml:space="preserve">and thro’ the Station Point </s>
          </p>
        </div>
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    </echo>
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