Gravesande, Willem Jacob 's, An essay on perspective
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              <pb o="13" file="0033" n="34" rhead="on PERSPECTIVE."/>
            and the Objects ſtand; </s>
            <s xml:id="echoid-s440" xml:space="preserve">and the Perſpective
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            Plane, as a Window between the Spectator and
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            the Objects, in which the Objects are requir’d
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            to be repreſented. </s>
            <s xml:id="echoid-s441" xml:space="preserve">But, in Practice, this Matter
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            muſt be quite otherwiſe conceiv’d; </s>
            <s xml:id="echoid-s442" xml:space="preserve">which I
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            ſhall now endeavour to explain as clear as poſ-
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            ſible.</s>
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            <s xml:id="echoid-s444" xml:space="preserve">Suppoſe then, that a Painter has a mind to
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            draw upon his Perſpective Plane, or Picture,
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            (whoſe Bigneſs is as he thinks fit) a Proſpect of
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            a Country, wherein are Trees, Houſes, Rivers, & </s>
            <s xml:id="echoid-s445" xml:space="preserve">c.
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            </s>
            <s xml:id="echoid-s446" xml:space="preserve">Now, from what has been ſaid, this Country
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            will be his Geometrical Plane; </s>
            <s xml:id="echoid-s447" xml:space="preserve">and he ought to
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            conſider his Perſpective Plane as a Window, up-
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            on which the Points thro’ which the Rays com-
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            ing from all the Points of the Objects towards
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            the Eye, muſt be found. </s>
            <s xml:id="echoid-s448" xml:space="preserve">But theſe Interſections
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            of the Rays and the Window cannot be deter-
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            min’d, unleſs by Lines being drawn in the Geo-
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            metrical Plane to the Baſe Line.</s>
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            <s xml:id="echoid-s450" xml:space="preserve">Now, it is impoſſible for Painters to draw Lines
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            of this Nature on the Ground; </s>
            <s xml:id="echoid-s451" xml:space="preserve">wherefore they
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            uſe another more convenient Geometrical Plane
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            thus. </s>
            <s xml:id="echoid-s452" xml:space="preserve">At the Foot of their Perſpective Plane,
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            they place a Plane, upon which are drawn in
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            Minature the Baſes of Houſes and Trees, which
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            are in the Country to be repreſented; </s>
            <s xml:id="echoid-s453" xml:space="preserve">and the
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            Seats of the Points which, in the Objects, are
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            elevated above the Country; </s>
            <s xml:id="echoid-s454" xml:space="preserve">always obſerving,
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            that there be the ſame Diſpoſition between the
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            Objects and their different Parts, upon this new
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            Geometrical Plane, as the Objects truly have in
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            the Country to be repreſented.</s>
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            <s xml:id="echoid-s456" xml:space="preserve">Now, to determine the Magnitude of the
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            Space the Figures muſt take up upon this Geo-
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            metrical Plane, a Painter muſt firſt chuſe the
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            Diſpoſition of his Eye in reſpect to the </s>
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