Gravesande, Willem Jacob 's, An essay on perspective

Table of figures

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        <div xml:id="echoid-div353" type="section" level="1" n="192">
          <p>
            <s xml:id="echoid-s2195" xml:space="preserve">
              <pb o="99" file="0173" n="201" rhead="on PERSPECTIVE."/>
            P S, and making the Point p be the ſame as P.
              <lb/>
            </s>
            <s xml:id="echoid-s2196" xml:space="preserve">then join each Diviſion of this Line, to the
              <lb/>
            correſpondent Diviſion of the Line h i; </s>
            <s xml:id="echoid-s2197" xml:space="preserve">and the
              <lb/>
            Dial ſought, will be drawn: </s>
            <s xml:id="echoid-s2198" xml:space="preserve">p being the Foot
              <lb/>
            of the Style, and p s the Horizontal Line.</s>
            <s xml:id="echoid-s2199" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div356" type="section" level="1" n="193">
          <head xml:id="echoid-head208" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s2200" xml:space="preserve">The Baſe Line is h i; </s>
            <s xml:id="echoid-s2201" xml:space="preserve">p s is the Horizontal
              <lb/>
              <note position="right" xlink:label="note-0173-01" xlink:href="note-0173-01a" xml:space="preserve">Fig. 66,
                <lb/>
              67.</note>
            Line; </s>
            <s xml:id="echoid-s2202" xml:space="preserve">p the Point of Sight; </s>
            <s xml:id="echoid-s2203" xml:space="preserve">and E O, or C P,
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            of Figure 66. </s>
            <s xml:id="echoid-s2204" xml:space="preserve">is the Length of the principal
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            Ray.</s>
            <s xml:id="echoid-s2205" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2206" xml:space="preserve">Now, ſuppoſe the Plane p s h i, to be ſet per-
              <lb/>
            pendicularly upon the Horizontal Dial, in ſuch
              <lb/>
            manner, that the Line h i coincides with H I,
              <lb/>
            and the Point o with O. </s>
            <s xml:id="echoid-s2207" xml:space="preserve">Suppoſe, moreover,
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            that thro’ the Extremity of the Style, which we
              <lb/>
            conſider as the Eye, Lines are drawn in the Ho-
              <lb/>
            rizontal Plane, parallel to the Hour-Lines of
              <lb/>
            the Dial; </s>
            <s xml:id="echoid-s2208" xml:space="preserve">it is evident, that theſe Lines will
              <lb/>
            meet the Horizontal Line p s, in the Point al-
              <lb/>
            ready prick’d down; </s>
            <s xml:id="echoid-s2209" xml:space="preserve">and conſequently ,
              <note symbol="*" position="right" xlink:label="note-0173-02" xlink:href="note-0173-02a" xml:space="preserve">13.</note>
            Appearances of the Hour-Lines, are the Lines
              <lb/>
            joining the Diviſions of the Lines h i and p s.</s>
            <s xml:id="echoid-s2210" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div359" type="section" level="1" n="194">
          <head xml:id="echoid-head209" xml:space="preserve">
            <emph style="sc">Remark</emph>
          .</head>
          <p>
            <s xml:id="echoid-s2211" xml:space="preserve">If the Line H I happens to meet the Meri-
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            dian; </s>
            <s xml:id="echoid-s2212" xml:space="preserve">the common Method, by the Horizontal
              <lb/>
            Dial, is eaſier than this.</s>
            <s xml:id="echoid-s2213" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div360" type="section" level="1" n="195">
          <head xml:id="echoid-head210" xml:space="preserve">
            <emph style="sc">Prob</emph>
          . II.</head>
          <head xml:id="echoid-head211" style="it" xml:space="preserve">123. To draw inclining Dials.</head>
          <p>
            <s xml:id="echoid-s2214" xml:space="preserve">Theſe Dials are drawn in the ſame manner as
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            Vertical ones; </s>
            <s xml:id="echoid-s2215" xml:space="preserve">the following Preparations being
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            firſt made.</s>
            <s xml:id="echoid-s2216" xml:space="preserve"/>
          </p>
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