Gravesande, Willem Jacob 's, An essay on perspective

Page concordance

< >
Scan Original
121 58
122
123
124
125 59
126 60
127
128
129
130 61
131 62
132 63
133 64
134
135
136
137 65
138 66
139 67
140 68
141
142
143
144 69
145 70
146 71
147 72
148
149
150
< >
page |< < (66) of 237 > >|
    <echo version="1.0RC">
      <text xml:lang="en" type="free">
        <div xml:id="echoid-div230" type="section" level="1" n="121">
          <pb o="66" file="0120" n="138" rhead="An ESSAY"/>
        </div>
        <div xml:id="echoid-div232" type="section" level="1" n="122">
          <head xml:id="echoid-head128" xml:space="preserve">
            <emph style="sc">Problem</emph>
          II.</head>
          <p style="it">
            <s xml:id="echoid-s1580" xml:space="preserve">82. </s>
            <s xml:id="echoid-s1581" xml:space="preserve">To find the Appearance of a Point above the
              <lb/>
            Geometrical Plane.</s>
            <s xml:id="echoid-s1582" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s1583" xml:space="preserve">Let H C be the Baſe Line: </s>
            <s xml:id="echoid-s1584" xml:space="preserve">And let T be the
              <lb/>
              <note position="left" xlink:label="note-0120-01" xlink:href="note-0120-01a" xml:space="preserve">Fig. 45.</note>
            accidental Point of the Lines perpendicular
              <lb/>
            to the Geometrical Plane. </s>
            <s xml:id="echoid-s1585" xml:space="preserve">This Point will
              <lb/>
            be in that Place of the Vertical Line,
              <note symbol="*" position="left" xlink:label="note-0120-02" xlink:href="note-0120-02a" xml:space="preserve">13.</note>
            it is cut by the Prolongation of the Line mea-
              <lb/>
            ſuring the Height of the Eye; </s>
            <s xml:id="echoid-s1586" xml:space="preserve">for this laſt
              <lb/>
            Line is parallel to the ſaid Perpendiculars. </s>
            <s xml:id="echoid-s1587" xml:space="preserve">And
              <lb/>
            ſo likewiſe the aforeſaid Point is the ſame as
              <lb/>
            the Point T of Fig. </s>
            <s xml:id="echoid-s1588" xml:space="preserve">44: </s>
            <s xml:id="echoid-s1589" xml:space="preserve">Let V be the Point of
              <lb/>
            Sight, S the Station Point, and Q the Station
              <lb/>
            Point of the upright perſpective Plane, to which
              <lb/>
            the inclined perſpective Plane is reduced . </s>
            <s xml:id="echoid-s1590" xml:space="preserve">
              <note symbol="*" position="left" xlink:label="note-0120-03" xlink:href="note-0120-03a" xml:space="preserve">81.</note>
            laſtly, let A be the Seat of the given Point.</s>
            <s xml:id="echoid-s1591" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div234" type="section" level="1" n="123">
          <head xml:id="echoid-head129" xml:space="preserve">
            <emph style="sc">Operation</emph>
          .</head>
          <p>
            <s xml:id="echoid-s1592" xml:space="preserve">Draw two Lines M P and P E ſeparately,
              <lb/>
            making a right Angle with each other; </s>
            <s xml:id="echoid-s1593" xml:space="preserve">in one
              <lb/>
            of which, aſſume P E, equal to the Height of
              <lb/>
            the given Point, whoſe Perſpective is ſought;
              <lb/>
            </s>
            <s xml:id="echoid-s1594" xml:space="preserve">and draw the Line E M, making an Angle with
              <lb/>
            M P, equal to the Angle of Inclination of the
              <lb/>
            perſpective Plane. </s>
            <s xml:id="echoid-s1595" xml:space="preserve">Again let fall the Perpen-
              <lb/>
            dicular A D from the Point A to the Baſe
              <lb/>
            Line, in which aſſume A L equal to P M, to-
              <lb/>
            wards the Baſe Line, when the perſpective
              <lb/>
            Plane is inclined towards the Objects (as we
              <lb/>
            have here ſuppoſed) but on the other Side of A,
              <lb/>
            when the perſpective Plane inclines towards the
              <lb/>
            Eye. </s>
            <s xml:id="echoid-s1596" xml:space="preserve">Then from the Point A, draw a Line
              <lb/>
            to the Point S, cutting the Baſe Line in B, and
              <lb/>
            joyn the Points L and Q, by a Line cutting the
              <lb/>
            Baſe Line in C. </s>
            <s xml:id="echoid-s1597" xml:space="preserve">This being done, draw </s>
          </p>
        </div>
      </text>
    </echo>
Impressum