Gravesande, Willem Jacob 's
,
An essay on perspective
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s
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0030
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An ESSAY
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a right Line drawn from the Eye parallel to the pro-
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poſed Line, terminates.</
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<
s
xml:id
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<
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<
s
xml:id
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xml:space
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preserve
">The Line C D being continued, will meet
<
unsure
/>
<
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/>
<
note
position
="
left
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xlink:label
="
note-0030-01
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xlink:href
="
note-0030-01a
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xml:space
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">Fig. 5.</
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the perſpective Plane in the Point E. </
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<
s
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preserve
">We are
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to prove, that its Appearance is a Part of the
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Line E H, drawn from the Point E, to the
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Point H, whereat the Line O H proceeding
<
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from the Eye parallel to the given Line C D,
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terminates.</
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>
<
s
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</
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<
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<
s
xml:id
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xml:space
="
preserve
">The Interſection of the perſpective Plane,
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and the Plane O D C, is the Repreſentation of the
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given Line. </
s
>
<
s
xml:id
="
echoid-s383
"
xml:space
="
preserve
">Now the Plane O D C, is a Part of the
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/>
Plane paſſing through the parallels O H and EC.</
s
>
<
s
xml:id
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xml:space
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"/>
</
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<
p
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<
s
xml:id
="
echoid-s385
"
xml:space
="
preserve
">Therefore, this Repreſentation is a Part of the
<
lb
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Interſection of the laſt mentioned Plane, and
<
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perſpective Plane; </
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>
<
s
xml:id
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xml:space
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">which Interſection is E H.</
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<
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<
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">Corollary</
emph
>
I.</
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">14. </
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<
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">All Lines parallel between themſelves, and be-
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ing produced, do fall upon the perſpective Plane, have
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Repreſentations, which being produced, will all con-
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cur in one Point.</
s
>
<
s
xml:id
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xml:space
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</
p
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<
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>
<
s
xml:id
="
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"
xml:space
="
preserve
">This is evident, becauſe but only one Line
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O H can be drawn from the Eye O, to the per-
<
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ſpective Plane, parallel to the ſaid Parallels, and
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becauſe all their Repreſentations are Parts of
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Lines concurring in the Point H.</
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>
<
s
xml:id
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xml:space
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"/>
</
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<
s
xml:id
="
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"
xml:space
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preserve
">And this Point is called the accidental Point of the
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/>
<
note
position
="
left
"
xlink:label
="
note-0030-02
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xlink:href
="
note-0030-02a
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xml:space
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">Def. 17.</
note
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ſaid Parallels.</
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<
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">Corollary</
emph
>
II.</
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<
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">15. </
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<
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xml:space
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">Two or more parallel Lines, which being produ-
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ced, do fall on the perſpective Plane, parallel to the Geo-
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metrical Plane, have their accidental Point in the
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Horizontal Line.</
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