Gravesande, Willem Jacob 's
,
An essay on perspective
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An ESSAY
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ſinding the reſt. </
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">But yet the Work may be
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ſhorten’d by the two precedent Problems, as we
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ſhall ſhew in the following Examples.</
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<
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I.</
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">To throw a Pentagon having one Side parallel to
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the Baſe Line, into Perſpective.</
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">Let A B C D E, be the propoſed Pentagon,
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wherein draw the Line B D which will be paral-
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lel to A E, becauſe the Pentagon is a regular
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one.</
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<
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">Now find the Repreſentation of the ſaid
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Lines A E and B D, and you will have the Re-
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preſentation of four of the Corners of the Pen-
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tagon; </
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<
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">and to determine the Repreſentation of
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the fifth Corner, find the Appearance of
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Line drawn from C to E, which in this Example
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is parallel to A B, which is ſuppoſed parallel
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to the Baſe Line.</
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<
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II.</
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">To throw a Parallelogram, divided into ſeveral
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other Parallelograms into Perſpective.</
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<
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">Let A B C D be a Parallelogram, divided
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<
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into ſeveral other Parallelograms.</
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">Draw the Line O G thro’ the Eye O parallel to
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the Side A D, cutting the Horizontal Line in G;
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<
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the Horizontal Line in F, and produce the Sides
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of the Parallelogram, and the Lines dividing it,
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to the Baſe Line; </
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A D and C B, and the Lines parallel thereto
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cut the Baſe Line, draw Lines to the Point G. </
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Alſo from the Points wherein A B and C D and
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their parallels cut the ſaid Line, draw Lines to
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the Point F, whoſe Interſections with </
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