Gravesande, Willem Jacob 's
,
An essay on perspective
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on PERSPECTIVE.
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P S, and making the Point p be the ſame as P.
<
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</
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<
s
xml:id
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xml:space
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">then join each Diviſion of this Line, to the
<
lb
/>
correſpondent Diviſion of the Line h i; </
s
>
<
s
xml:id
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xml:space
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">and the
<
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Dial ſought, will be drawn: </
s
>
<
s
xml:id
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xml:space
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">p being the Foot
<
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of the Style, and p s the Horizontal Line.</
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</
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<
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.</
head
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<
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<
s
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xml:space
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">The Baſe Line is h i; </
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>
<
s
xml:id
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xml:space
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">p s is the Horizontal
<
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xml:space
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">Fig. 66,
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67.</
note
>
Line; </
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>
<
s
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">p the Point of Sight; </
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>
<
s
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xml:space
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">and E O, or C P,
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of Figure 66. </
s
>
<
s
xml:id
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xml:space
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">is the Length of the principal
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Ray.</
s
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<
s
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</
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<
p
>
<
s
xml:id
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xml:space
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">Now, ſuppoſe the Plane p s h i, to be ſet per-
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pendicularly upon the Horizontal Dial, in ſuch
<
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manner, that the Line h i coincides with H I,
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and the Point o with O. </
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<
s
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xml:space
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">Suppoſe, moreover,
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that thro’ the Extremity of the Style, which we
<
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/>
conſider as the Eye, Lines are drawn in the Ho-
<
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rizontal Plane, parallel to the Hour-Lines of
<
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the Dial; </
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<
s
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xml:space
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">it is evident, that theſe Lines will
<
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meet the Horizontal Line p s, in the Point al-
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ready prick’d down; </
s
>
<
s
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xml:space
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preserve
">and conſequently ,
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xlink:label
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xml:space
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">13.</
note
>
Appearances of the Hour-Lines, are the Lines
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joining the Diviſions of the Lines h i and p s.</
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</
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<
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.</
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<
s
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xml:space
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">If the Line H I happens to meet the Meri-
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dian; </
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<
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">the common Method, by the Horizontal
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Dial, is eaſier than this.</
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</
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<
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style
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">Prob</
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>
. II.</
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style
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it
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xml:space
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">123. To draw inclining Dials.</
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>
<
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<
s
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xml:space
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">Theſe Dials are drawn in the ſame manner as
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Vertical ones; </
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<
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firſt made.</
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