Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div360" type="section" level="1" n="195">
          <pb o="100" file="0174" n="202" rhead="An ESSAY"/>
          <p>
            <s xml:id="echoid-s2217" xml:space="preserve">Draw the Line e c, equal to the Length of
              <lb/>
              <note position="left" xlink:label="note-0174-01" xlink:href="note-0174-01a" xml:space="preserve">Fig. 68.</note>
            the Style of the Horizontal Dial; </s>
            <s xml:id="echoid-s2218" xml:space="preserve">and, at its
              <lb/>
            two Extremities raiſe the Perpendiculars e o
              <lb/>
            and c p: </s>
            <s xml:id="echoid-s2219" xml:space="preserve">Then draw the Line c G, thro’ the
              <lb/>
            Point c, equal in Length to the Style of the
              <lb/>
            Dial to be drawn; </s>
            <s xml:id="echoid-s2220" xml:space="preserve">making an Angle with c e,
              <lb/>
            equal to the Inclination of the Dial-Plane. </s>
            <s xml:id="echoid-s2221" xml:space="preserve">Af-
              <lb/>
            ter which, draw the Line o G p, thro’ the Ex-
              <lb/>
            tremity G of the ſaid Line, perpendicular there-
              <lb/>
            to. </s>
            <s xml:id="echoid-s2222" xml:space="preserve">This Preparation being finiſh’d, we uſe the
              <lb/>
            Operations of the precedent Problem, in making
              <lb/>
            E O and C P, in the Horizontal Dial, equal to
              <lb/>
            e o and c p of this Figure; </s>
            <s xml:id="echoid-s2223" xml:space="preserve">and o p, in the Dial
              <lb/>
            to be drawn, equal to op of this Figure; </s>
            <s xml:id="echoid-s2224" xml:space="preserve">in
              <lb/>
            which, the Point G is the Foot of the Style.</s>
            <s xml:id="echoid-s2225" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2226" xml:space="preserve">If it happens, in the aforeſaid Preparation,
              <lb/>
              <note position="left" xlink:label="note-0174-02" xlink:href="note-0174-02a" xml:space="preserve">Fig. 69.</note>
            that the Line p o cuts the Line e c; </s>
            <s xml:id="echoid-s2227" xml:space="preserve">E O muſt
              <lb/>
            not then be aſſum’d in the ſame Line, in the
              <lb/>
            Horizontal Dial, as otherwiſe it muſt have
              <lb/>
            been; </s>
            <s xml:id="echoid-s2228" xml:space="preserve">but, in that Line, continued on the other
              <lb/>
            ſide of the Foot of the Style.</s>
            <s xml:id="echoid-s2229" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2230" xml:space="preserve">The Demonſtration of this Problem, is the
              <lb/>
            ſame as that of the precedent one; </s>
            <s xml:id="echoid-s2231" xml:space="preserve">in conſider-
              <lb/>
            ing the Angle p o Q, equal to the Angle G c e,
              <lb/>
            which is equal to the Inclination of the Plane.</s>
            <s xml:id="echoid-s2232" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2233" xml:space="preserve">We might have further ſhewn the Uſe of
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            Perſpective, in facilitating the Operations of
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            Dialling: </s>
            <s xml:id="echoid-s2234" xml:space="preserve">But this would be deviating from our
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            Subject; </s>
            <s xml:id="echoid-s2235" xml:space="preserve">and ſo we ſhall content our ſelves with
              <lb/>
            this Short Eſſay, touching the moſt common and
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            uſeful Problem in Dialling.</s>
            <s xml:id="echoid-s2236" xml:space="preserve"/>
          </p>
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