Gravesande, Willem Jacob 's, An essay on perspective

Table of contents

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[51.] Remarks.
[52.] Corollary.
[53.] Problem II.
[54.] Remark.
[55.] Problem III.
[56.] Method. II.
[57.] Problem IV.
[58.] Example I.
[59.] Example II.
[60.] Remarks.
[61.] Example III. 48. To throw a circle into Perſpective.
[62.] Remarks.
[63.] Prob. V. 50. To find the Repreſentation of a Point, elevated above the Geometrical Planc.
[64.] Operation.
[65.] Demonstration.
[66.] Prob. VI. 52. To throm a Pyramid, or Cone, into Perſpective.
[67.] 53. To determine the viſible Part of the Baſe of a Cone.
[68.] Operation.
[69.] Demonstration.
[70.] Remarks.
[71.] Problem VII. 55. To find the Perſpective of a Line, perpendicular to the Geometrical Plane.
[72.] Operation.
[73.] Demonstration.
[74.] Method II.
[75.] Demonstration.
[76.] Method III.
[77.] Operation, Without Compaſſes.
[78.] Demonstration.
[79.] Scholium.
[80.] Corollary.
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          <pb o="101" file="0177" n="206" rhead="on PERSPECTIVE."/>
          <figure number="71">
            <image file="0177-01" xlink:href="http://echo.mpiwg-berlin.mpg.de/zogilib?fn=/permanent/library/xxxxxxxx/figures/0177-01"/>
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        <div xml:id="echoid-div363" type="section" level="1" n="196">
          <head xml:id="echoid-head212" style="it" xml:space="preserve">The Uſe of the
            <emph style="sc">Camera</emph>
            <emph style="sc">Obscura</emph>
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          in Deſigning.</head>
          <head xml:id="echoid-head213" xml:space="preserve">
            <emph style="sc">Advertisement</emph>
          .</head>
          <p style="it">
            <s xml:id="echoid-s2237" xml:space="preserve">EVery one knows how eaſy it is by one Convex Glaſs
              <lb/>
            only, to repreſent outward Objects in any darken’d
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            Place, according to their natural Appearances, where
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            the Livelineſs of Colours, and the Diverſity of Mo-
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            tions, are wonderfully pleaſant to behold; </s>
            <s xml:id="echoid-s2238" xml:space="preserve">and it is
              <lb/>
            ſo eaſy to make this Invention uſeful in Deſigning,
              <lb/>
            that our treating of it ſo fully as we have done, is
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            undoubtedly ſomething neceſſary.</s>
            <s xml:id="echoid-s2239" xml:space="preserve"/>
          </p>
          <p style="it">
            <s xml:id="echoid-s2240" xml:space="preserve">A few Hints and Obſervations ſeem to be ſufficient
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            for putting a diligent Perſon in the way of contriving
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            himſelf ſome Machine to perform the Uſes hereafter
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            mentioned; </s>
            <s xml:id="echoid-s2241" xml:space="preserve">whence we might have let him bad the
              <lb/>
            Pleaſure of the Invention himſelf, after it was made
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            eaſy to him. </s>
            <s xml:id="echoid-s2242" xml:space="preserve">And this indeed is what I firſt reſolv’d
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            upon; </s>
            <s xml:id="echoid-s2243" xml:space="preserve">but afterwards conſidering that in the Con-
              <lb/>
            ſtruction of a Machine for facilitating the Buſineſs of
              <lb/>
            Deſigning, ſeveral Things cannot be foreknown till
              <lb/>
            try’d; </s>
            <s xml:id="echoid-s2244" xml:space="preserve">and that much Time may be ſpent in vain, and
              <lb/>
            ſeveral Methods attempted, before one of theſe Ma-
              <lb/>
            chines can be made ſimple and uſeful, as I have found
              <lb/>
            by Experierce: </s>
            <s xml:id="echoid-s2245" xml:space="preserve">Therefore, that others may not be at
              <lb/>
            this Trouble, I ſhall here lay down the Deſcription of
              <lb/>
            two Machines (hoping it will not be unacceptable)
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            which after ſeveral Alterations, in my Opinion, are
              <lb/>
            now made convenient enough.</s>
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          </p>
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