Gravesande, Willem Jacob 's, An essay on perspective

Table of handwritten notes

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        <div xml:id="echoid-div266" type="section" level="1" n="139">
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            the Lines themſelves, and T the Accidental Point
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            oſ Perpendiculars to the Geometrical Plane.</s>
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        <div xml:id="echoid-div268" type="section" level="1" n="140">
          <head xml:id="echoid-head146" xml:space="preserve">
            <emph style="sc">Operation</emph>
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          <p>
            <s xml:id="echoid-s1761" xml:space="preserve">Continue the Line A B until it meets the
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            Baſe Line in G, and draw the Line G D, which
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            cut in a and b by Lines drawn from A and B to
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            the Eye. </s>
            <s xml:id="echoid-s1762" xml:space="preserve">Then draw the Lines a F and T b In-
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            terſecting each other in X; </s>
            <s xml:id="echoid-s1763" xml:space="preserve">and a x will be the
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            Appearance ſought.</s>
            <s xml:id="echoid-s1764" xml:space="preserve"/>
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        <div xml:id="echoid-div269" type="section" level="1" n="141">
          <head xml:id="echoid-head147" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1765" xml:space="preserve">Becauſe a b is the Repreſentation of A
              <note symbol="*" position="left" xlink:label="note-0132-01" xlink:href="note-0132-01a" xml:space="preserve">43.</note>
            the Appearance of the inclin’d Line is one Part
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            of a F. </s>
            <s xml:id="echoid-s1766" xml:space="preserve">But the Extremity of the inclin’d Line
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            is in a Perpendicular to the Geometrical Plane
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            raiſed at the Point B; </s>
            <s xml:id="echoid-s1767" xml:space="preserve">therefore the Repreſen-
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            tation of the ſaid Extremity is in T b, and con-
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            ſequently x in the Interſection of this Line and
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            a F.</s>
            <s xml:id="echoid-s1768" xml:space="preserve"/>
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        <div xml:id="echoid-div271" type="section" level="1" n="142">
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            <emph style="sc">Method</emph>
          III.</head>
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            <s xml:id="echoid-s1769" xml:space="preserve">91. </s>
            <s xml:id="echoid-s1770" xml:space="preserve">Draw F H thro’ the Accidental Point of
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            the inclin’d Lines, parallel to the Baſe Line,
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            and equal to o F in Fig. </s>
            <s xml:id="echoid-s1771" xml:space="preserve">48. </s>
            <s xml:id="echoid-s1772" xml:space="preserve">then a is the Perpen-
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              <note position="left" xlink:label="note-0132-02" xlink:href="note-0132-02a" xml:space="preserve">Fig. 49.</note>
            dicular of the Foot of the inclin’d Line whoſe
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            Perſpective a x may be found as directed n. </s>
            <s xml:id="echoid-s1773" xml:space="preserve">70.</s>
            <s xml:id="echoid-s1774" xml:space="preserve"/>
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