Gravesande, Willem Jacob 's, An essay on perspective

Table of figures

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[31] page 48.Plate 13.Fig. 32.V S R L P B D Q T M I F A E Y C G O H Z N
[32] page 52.Plate. 14.Fig. 34D C F G A B H L E
[33] Fig. 33S X 8 1 h 6 g 3 z q 9 m 2 4 m a 5 Y
[34] Fig. 35O M D P T Q R m p q B A S C
[35] page 56.Plate. 15F H O Z D G
[36] Fig. 36T N M L a R Q E I A C P B
[37] Fig. 37F S V T I E M A N X P C B
[38] page 58.Plate. 16Fig. 39Fig. 38F Q O p l r s 1 2 3 4 G
[39] page 60.Plate. 17F V
[40] Fig. 40c θ b e a F G H I K L A B E C D
[41] page 64Plate. 18.d v
[42] Fig. 41E b a G F H C B A D
[43] Fig. 42G Q A M I S E H T B L Z F P a X Y N C D R O
[44] page 68Plate. 19Fig. 43B D E a G H I C F L
[45] Fig. 44O V X S H I T
[46] Fig. 45Q F V X S a H B C D E L M P T A
[47] page 72Plate. 20Fig. 46V I X a E M P A T
[48] Fig. 47V F X a Q G H D N A T R
[49] Page 34.Plate. 21Fig. 48F O D X S b a G N A E T B P C
[50] Fig. 49H F O D G X a M N L R Q
[51] Page 36Plate 22Fig. 50O R E G N S M
[52] Fig. 51I H T a X
[53] Fig. 52C D X I H G a F E L b T
[54] Fig. 53H I F T x d X L B C
[55] page 64.Plate 23.Fig. 54O M P Q t A X x Q R N
[56] Fig. 55G F b T L a
[57] Fig. 56I F a X b E T C P
[58] page 66.Plate. 24.Fig. 57E A Z C P B
[59] Fig. 58F O D I a b
[60] Fig. 59F E Z C A B
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          <p>
            <s xml:id="echoid-s850" xml:space="preserve">
              <pb o="33" file="0065" n="72" rhead="on PERSPECTIVE."/>
            firſt found ; </s>
            <s xml:id="echoid-s851" xml:space="preserve">and then if Lines be drawn
              <note symbol="*" position="right" xlink:label="note-0065-01" xlink:href="note-0065-01a" xml:space="preserve">47.</note>
            the Repreſentation of the Vertex touching the
              <lb/>
            Repreſentation of the Baſe, the Repreſentation
              <lb/>
            of the Cone will be had.</s>
            <s xml:id="echoid-s852" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s853" xml:space="preserve">But ſince, according to this Manner, we are
              <lb/>
            obliged to find the Perſpective of all the Baſe;
              <lb/>
            </s>
            <s xml:id="echoid-s854" xml:space="preserve">whereas it often cannot be all ſeen; </s>
            <s xml:id="echoid-s855" xml:space="preserve">we may de-
              <lb/>
            termine, by the following Method, what Part
              <lb/>
            of the Baſe is viſible, and ſo only find the Re-
              <lb/>
            preſentation thereof. </s>
            <s xml:id="echoid-s856" xml:space="preserve">And then, to compleat
              <lb/>
            the Cone, we draw Lines from the Extremities
              <lb/>
            of the viſible Part of the Baſe, to the Repreſen-
              <lb/>
            tation of the Vertex.</s>
            <s xml:id="echoid-s857" xml:space="preserve"/>
          </p>
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        <div xml:id="echoid-div123" type="section" level="1" n="67">
          <head xml:id="echoid-head72" style="it" xml:space="preserve">53. To determine the viſible Part of the Baſe of
            <lb/>
          a Cone.</head>
          <p>
            <s xml:id="echoid-s858" xml:space="preserve">Let the Circle L I F be the Baſe of a Cone
              <lb/>
              <note position="right" xlink:label="note-0065-02" xlink:href="note-0065-02a" xml:space="preserve">Fig. 21.</note>
            in the Geometrical Plane, and A the Center
              <lb/>
            thereof.</s>
            <s xml:id="echoid-s859" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div125" type="section" level="1" n="68">
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            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s860" xml:space="preserve">Aſſume P Q ſomewhere in the Baſe Line,
              <lb/>
            equal to the Semidiameter of the Circle L F;
              <lb/>
            </s>
            <s xml:id="echoid-s861" xml:space="preserve">and from the Point P, raiſe P D G perpendicu-
              <lb/>
            lar to the Baſe Line, meeting the Horizontal
              <lb/>
            Line in G; </s>
            <s xml:id="echoid-s862" xml:space="preserve">and in this Perpendicular, make
              <lb/>
            P D equal to the Height of the Cone; </s>
            <s xml:id="echoid-s863" xml:space="preserve">and draw
              <lb/>
            the Line Q D H, meeting the Horizontal Line
              <lb/>
            in H. </s>
            <s xml:id="echoid-s864" xml:space="preserve">Then, about the Point A as a Center,
              <lb/>
            and with the Radius G H, draw the Circle B C E; </s>
            <s xml:id="echoid-s865" xml:space="preserve">
              <lb/>
            and from the ſaid Point A, draw a Line to the
              <lb/>
            Station Point S: </s>
            <s xml:id="echoid-s866" xml:space="preserve">Biſect A S in R; </s>
            <s xml:id="echoid-s867" xml:space="preserve">and about
              <lb/>
            R, as a Center, with the Radius R A, deſcribe
              <lb/>
            the Circular Arc B A C, cutting the Circle BEC
              <lb/>
            in the Points B and C. </s>
            <s xml:id="echoid-s868" xml:space="preserve">Draw the Lines B A F,
              <lb/>
            and C A L; </s>
            <s xml:id="echoid-s869" xml:space="preserve">and the viſible Portion, (L I F) </s>
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