Gravesande, Willem Jacob 's
,
An essay on perspective
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The PREFACE.
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This I have done ſometimes; </
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would have been very long and troubleſome.
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</
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<
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xml:space
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">In Geometry, the eaſieſt and ſhorteſt Way, is
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not always that which leads to Diſcoveries.</
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">In the following Chapter, the Practice of Per-
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ſpective upon the perſpective Plane, or Picture,
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conſider’d as upright, is explain’d: </
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xml:space
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">Wherein,
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among the different Ways laid down for the
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Solution of general Problems, you will find
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ſome effected by a Ruler only; </
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xml:space
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">ſo that after
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ſome Preparations, all Kinds of Objects may
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be drawn without Compaſſes, and that eaſier
<
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than by the common Operations. </
s
>
<
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xml:space
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">In that
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Problem, to find the Appearance of a Point
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out of the Geometrical Plane, it is commonly
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conſider’d as the Extremity of a Perpendicu-
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lar, whoſe Repreſentation muſt first be found,
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before that of the Point can be had. </
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>
<
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xml:space
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">But here
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we avoid this round-about Way, and ſhew how
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to find the Appearance of the Point given,
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without being obliged to find the Perſpective
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of its Seat.</
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<
s
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xml:space
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">As to the Appearance of a Cone and Cy-
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linder, we determine the viſible Portions of
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the Baſe, and by this means avoid the uſe-
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leſs Operations which the common Way is
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ſubject to. </
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>
<
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xml:space
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">It is very difficult, if not impoſ-
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ſible, to throw a Sphere into Perſpective, by
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means of general Problems; </
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preſentation of the Torus of a Column, it </
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