Gravesande, Willem Jacob 's, An essay on perspective

List of thumbnails

< >
191
191 (95) 		192
192 (96)
193
193 		194
194
195
195 		196
196
197
197 		198
198
199
199 (97) 		200
200 (98)
< >
page |< < (97) of 237 > >|
    <echo version="1.0RC">
      <text xml:lang="en" type="free">
        <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,
                <lb/>
              115, 117.</note>
            Shadows will be had.</s>
            <s xml:id="echoid-s2161" xml:space="preserve"/>
          </p>
        </div>
        <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
              <lb/>
            how to draw the Hour Lines upon any
              <lb/>
            Kind of Plane, by means of an Horizon-
              <lb/>
            tal Dial.</s>
            <s xml:id="echoid-s2164" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2165" xml:space="preserve">PERSPECTIVE is not only uſeſul in
              <lb/>
            drawing, but likewiſe in other Parts of Ma-
              <lb/>
            thematicks, and principally in Dialling: </s>
            <s xml:id="echoid-s2166" xml:space="preserve">For if
              <lb/>
            the Extremity of the Style be conceived as the
              <lb/>
            Eye, and the Sun’s Rays as viſual Rays, all
              <lb/>
            poſſible Kinds of Dials may be drawn for the
              <lb/>
            ſame Latitude, by Means of an Horizontal Dial,
              <lb/>
            as we are now going to ſhew,</s>
          </p>
          <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
              <lb/>
            made for any given Latitude; </s>
            <s xml:id="echoid-s2169" xml:space="preserve">E F its Style, and
              <lb/>
              <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
              <lb/>
            drawn. </s>
            <s xml:id="echoid-s2170" xml:space="preserve">Now if this Plane be ſo ſituated, that
              <lb/>
            the Extremity of its Style F G, coincides with
              <lb/>
            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
              <lb/>
            Lines of the Horizontal Dial A B C D, be found
              <lb/>
            upon the Plane H I M L, in conceiving the
              <lb/>
            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
              <lb/>
            Perſpective, at the ſame Time that it falls
              <lb/>
            upon the Hour Line, whereof it is the Per-
              <lb/>
            ſpective; </s>
            <s xml:id="echoid-s2172" xml:space="preserve">and conſequently, the ſaid Shadow
              <lb/>
            will ſhew the ſame Hour upon the Plane H I M L,
              <lb/>
            that it ſhews upon the Horizontal Dial: </s>
            <s xml:id="echoid-s2173" xml:space="preserve"/>
          </p>
        </div>
      </text>
    </echo>
Impressum