Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div349" type="section" level="1" n="190">
          <p>
            <s xml:id="echoid-s2160" xml:space="preserve">
              <pb o="97" file="0171" n="199" rhead="on PERSPECTIVE."/>
            Points be found , the Repreſentations of
              <note symbol="*" position="right" xlink:label="note-0171-01" xlink:href="note-0171-01a" xml:space="preserve">109,
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              115, 117.</note>
            Shadows will be had.</s>
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        <div xml:id="echoid-div351" type="section" level="1" n="191">
          <head xml:id="echoid-head205" xml:space="preserve">CHAP. IX.</head>
          <p style="it">
            <s xml:id="echoid-s2162" xml:space="preserve">The Uſe of Perſpective in Dialling; </s>
            <s xml:id="echoid-s2163" xml:space="preserve">ſhewing
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            how to draw the Hour Lines upon any
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            Kind of Plane, by means of an Horizon-
              <lb/>
            tal Dial.</s>
            <s xml:id="echoid-s2164" xml:space="preserve"/>
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          <p>
            <s xml:id="echoid-s2165" xml:space="preserve">PERSPECTIVE is not only uſeſul in
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            drawing, but likewiſe in other Parts of Ma-
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            thematicks, and principally in Dialling: </s>
            <s xml:id="echoid-s2166" xml:space="preserve">For if
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            the Extremity of the Style be conceived as the
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            Eye, and the Sun’s Rays as viſual Rays, all
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            poſſible Kinds of Dials may be drawn for the
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            ſame Latitude, by Means of an Horizontal Dial,
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            as we are now going to ſhew,</s>
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          <p>
            <s xml:id="echoid-s2167" xml:space="preserve">121. </s>
            <s xml:id="echoid-s2168" xml:space="preserve">Let A B C D be an Horizontal Dial
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            made for any given Latitude; </s>
            <s xml:id="echoid-s2169" xml:space="preserve">E F its Style, and
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              <note position="right" xlink:label="note-0171-02" xlink:href="note-0171-02a" xml:space="preserve">Fig. 65.</note>
            H I M L a Plane, upon which a Dial is to be
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            drawn. </s>
            <s xml:id="echoid-s2170" xml:space="preserve">Now if this Plane be ſo ſituated, that
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            the Extremity of its Style F G, coincides with
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            the Extremity of the Style of the Horizontal
              <lb/>
            Dial; </s>
            <s xml:id="echoid-s2171" xml:space="preserve">and if the Perſpective of one of the Hour
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            Lines of the Horizontal Dial A B C D, be found
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            upon the Plane H I M L, in conceiving the
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            Point F as the Eye, it is evident , that
              <note symbol="*" position="right" xlink:label="note-0171-03" xlink:href="note-0171-03a" xml:space="preserve">2.</note>
            Shadow of the Point F, will fall upon the ſaid
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            Perſpective, at the ſame Time that it falls
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            upon the Hour Line, whereof it is the Per-
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            ſpective; </s>
            <s xml:id="echoid-s2172" xml:space="preserve">and conſequently, the ſaid Shadow
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            will ſhew the ſame Hour upon the Plane H I M L,
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            that it ſhews upon the Horizontal Dial: </s>
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