Gravesande, Willem Jacob 's, An essay on perspective

Page concordance

< >
Scan Original
191 95
192 96
193
194
195
196
197
198
199 97
200 98
201 99
202 100
203
204
205
206 101
207 102
208 103
209 104
210 105
211 106
212 107
213 108
214 109
215 110
216 111
217 112
218 113
219 114
220 115
< >
page |< < (95) of 237 > >|
    <echo version="1.0RC">
      <text xml:lang="en" type="free">
        <div xml:id="echoid-div345" type="section" level="1" n="188">
          <p>
            <s xml:id="echoid-s2133" xml:space="preserve">
              <pb o="95" file="0165" n="191" rhead="on PERSPECTIVE."/>
            lar drawn from the Eye to the Geometrical
              <lb/>
            Plane, meets the ſaid Plane; </s>
            <s xml:id="echoid-s2134" xml:space="preserve">and T the Per-
              <lb/>
            ſpective of that Point, found by the aforegoing
              <lb/>
            Problem. </s>
            <s xml:id="echoid-s2135" xml:space="preserve">Now make F L and C R, equal to the
              <lb/>
            Length of the given Lines; </s>
            <s xml:id="echoid-s2136" xml:space="preserve">and about the
              <lb/>
            Points R and S, as Centers, with the Radius
              <lb/>
            M N or P Q, deſcribe two Arcs cutting the
              <lb/>
            Perpendiculars H D and G H, in the Points
              <lb/>
            X and S: </s>
            <s xml:id="echoid-s2137" xml:space="preserve">Then fix the Extremities of the
              <lb/>
            Threads, which before were faſten’d to the
              <lb/>
            Points F and E, to the Points L and S; </s>
            <s xml:id="echoid-s2138" xml:space="preserve">and alſo
              <lb/>
            the Extremities of thoſe two Threads, which
              <lb/>
            were before faſten’d to the Points C and D, in
              <lb/>
            the Points R and X: </s>
            <s xml:id="echoid-s2139" xml:space="preserve">Then moving the two
              <lb/>
            Rulers, until the Threads S P and X M, croſs
              <lb/>
            each other in the Point T, mark the Point O,
              <lb/>
            wherein the two other Threads croſs one another,
              <lb/>
            through which, and the Point B, draw the
              <lb/>
            indefinite Line B O V: </s>
            <s xml:id="echoid-s2140" xml:space="preserve">this being done, tranſ-
              <lb/>
            poſe the Lines of the Geometrical Plane, ſo that
              <lb/>
            the Point B, coincides with the Point O, and
              <lb/>
            the Line B O, with O V. </s>
            <s xml:id="echoid-s2141" xml:space="preserve">And by the precedent
              <lb/>
            Problem, find the Appearances of the Feet of
              <lb/>
            the Perpendiculars, and you will have the Re-
              <lb/>
            preſentations of their Extremities.</s>
            <s xml:id="echoid-s2142" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div347" type="section" level="1" n="189">
          <head xml:id="echoid-head203" xml:space="preserve">
            <emph style="sc">Demonstration</emph>
          .</head>
          <p>
            <s xml:id="echoid-s2143" xml:space="preserve">If a Plane be ſuppoſed to paſs through the
              <lb/>
            Extremities of the Perpendiculars, it will be
              <lb/>
            parallel to the Geometrical Plane, and conſe-
              <lb/>
            quently, likewiſe to the perſpective Plane, be-
              <lb/>
            cauſe all the Perpendiculars are ſuppoſed equal.
              <lb/>
            </s>
            <s xml:id="echoid-s2144" xml:space="preserve">But the Figure formed by the Extremities of
              <lb/>
            the Perpendiculars in the ſaid Plane, is ſimilar
              <lb/>
            and equal to that form’d by their Feet in the
              <lb/>
            Geometrical Plane: </s>
            <s xml:id="echoid-s2145" xml:space="preserve">and therefore, the </s>
          </p>
        </div>
      </text>
    </echo>
Impressum