Gravesande, Willem Jacob 's
,
An essay on perspective
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on PERSPECTIVE.
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<
s
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">The Operation of Prob. </
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<
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<
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here, but with this Difference (ſee Fig. </
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<
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ſaid Prob.) </
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<
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">that whereas a I in the ſaid Problem
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is perpendicular to the Baſe Line, here it muſt
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make an Angle with the Baſe Line, equal to the
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Angle of Inclination of the given Lines.</
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<
s
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<
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. XIV.</
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<
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">To throw a Body into Perſpective, having
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ſome one or all of its Sides inclined to the Geometri-
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cal Plane.</
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<
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">The Appearances of the Lines forming the
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Angles of the propoſed Body muſt be found: </
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<
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this may be eaſily done by Prob. </
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takes in all the Caſes. </
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<
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">And in this Manner the
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Appearance of a Pyramid, an inclined Priſm,
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& </
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<
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">c. </
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<
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">may be found. </
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<
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">But nevertheleſs, it hap-
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pens ſometimes, that the Operations of the pre-
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cedent Problem may be abbreviated; </
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<
s
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">as when
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the Extremity of ſeveral Lines are found in one
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and the ſame Line, or when inclined Lines, that
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have difficult accidental Points, interſect one
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another, and ſo mutually determine each other.
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</
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<
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">This will appear manifeſt by the following Ex-
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amples.</
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<
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I.</
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">To throw ſeveral parallel Shores which ſtrengthen a
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Wall, into Perſpective.</
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<
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<
s
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">I ſuppoſe here that the Baſes of theſe Shores,
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<
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">Fig. 38.</
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which are the Places where they meet the Sur-
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face of the Ground, are all in a right Line, pa-
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rallel to the Side of the Wall; </
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<
s
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">and then the
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faid Shores may be thrown into Perſpective in
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the following Manner: </
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<
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">Having firſt found
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