Gravesande, Willem Jacob 's, An essay on perspective

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        <div xml:id="echoid-div365" type="section" level="1" n="198">
          <p>
            <s xml:id="echoid-s2282" xml:space="preserve">
              <pb o="104" file="0180" n="209" rhead="An ESSAY on"/>
            out the Camera Obſcura, is ſimilar to that which
              <lb/>
            they form, after having paſſed through the Glaſs:
              <lb/>
            </s>
            <s xml:id="echoid-s2283" xml:space="preserve">Therefore the Rays which fall upon the Paper in
              <lb/>
            the Camera Obſcura, likewiſe give the true Re-
              <lb/>
            preſentation of the Objects thereon. </s>
            <s xml:id="echoid-s2284" xml:space="preserve">Which was
              <lb/>
            to be demouſtrated.</s>
            <s xml:id="echoid-s2285" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2286" xml:space="preserve">Theſe Objects appear inverted, becauſe the
              <lb/>
            Rays croſs each other in paſſing through the Glaſs;
              <lb/>
            </s>
            <s xml:id="echoid-s2287" xml:space="preserve">thoſe coming from above going below, &</s>
            <s xml:id="echoid-s2288" xml:space="preserve">c.</s>
            <s xml:id="echoid-s2289" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div366" type="section" level="1" n="199">
          <head xml:id="echoid-head217" xml:space="preserve">
            <emph style="sc">Theorem</emph>
          II.</head>
          <p style="it">
            <s xml:id="echoid-s2290" xml:space="preserve">3. </s>
            <s xml:id="echoid-s2291" xml:space="preserve">The Reflection which the Rays of Light ſuffer
              <lb/>
            upon a plain Mirrour or Speculum, before they fall
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            upon a Convex Glaſs, no-wiſe deforms the Repreſen-
              <lb/>
            tation of Objects.</s>
            <s xml:id="echoid-s2292" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2293" xml:space="preserve">This is evident: </s>
            <s xml:id="echoid-s2294" xml:space="preserve">For the Speculum reflects the
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            Rays in the ſame Order as it receives them.</s>
            <s xml:id="echoid-s2295" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2296" xml:space="preserve">Now to ſhew the Uſe that may be drawn from
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            the Camera Obſcura in Deſigning, I ſhall here lay
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            down the Deſcription and Uſe of Two Machines,
              <lb/>
            which I uſe for this End.</s>
            <s xml:id="echoid-s2297" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div367" type="section" level="1" n="200">
          <head xml:id="echoid-head218" style="it" xml:space="preserve">The Deſcription of the Firſt Machine.</head>
          <p>
            <s xml:id="echoid-s2298" xml:space="preserve">4. </s>
            <s xml:id="echoid-s2299" xml:space="preserve">This Machine is ſomething in Figure of a
              <lb/>
            Chair, (ſuch as People are carried in) the back Part
              <lb/>
            of the Top is rounded, and its Foreſide P Q ſwells
              <lb/>
            out in the middle: </s>
            <s xml:id="echoid-s2300" xml:space="preserve">Vide Fig. </s>
            <s xml:id="echoid-s2301" xml:space="preserve">70. </s>
            <s xml:id="echoid-s2302" xml:space="preserve">which repreſents
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              <note position="left" xlink:label="note-0180-01" xlink:href="note-0180-01a" xml:space="preserve">Fig. 70.</note>
            the Machine, the Side whereof oppoſite to the
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            Door, is ſuppoſed to be raiſed up, that ſo its In-
              <lb/>
            ſide may be ſeen.</s>
            <s xml:id="echoid-s2303" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2304" xml:space="preserve">5. </s>
            <s xml:id="echoid-s2305" xml:space="preserve">The Board A within-ſide, ſerves as a Ta-
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            ble, and turns upon two Iron-pins, going into
              <lb/>
            the Wood of the Fore-ſide of the Machine, and is
              <lb/>
            ſuſtain’d by two ſmall Chains, that ſo the ſaid
              <lb/>
            Table may be lifted up; </s>
            <s xml:id="echoid-s2306" xml:space="preserve">and therefore one </s>
          </p>
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